Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On Thu, 2018-08-02 at 11:00 +0100, Tvrtko Ursulin wrote:
> [Picking this point in the thread to reply on some points mentioned
> by
> folks in the whole thread.]
>
> I don't remember if any patches from Lionel's series actually had r-
> b's,
> but a few people including myself have certainly been reviewing them.
> If
> I had applied the final r-b I wouldn't have made much difference due
> lack of userspace and disagreement on the DoS mitigation story. So
> to
> say effectively put your money where your mouth is and review is not
> entirely fair.
>
> Suggestion to add a master sysfs switch was to alleviate the DoS
> concerns because dynamic switching has a cost towards all GPU
> clients,
> not that it just has potential to slow down media.
>
> Suggestion was also that this switch becomes immutable and defaults
> to
> "allow" on Gen11 onwards.
>
> I preferred sysfs versus a modparam since it makes testing (Both for
> developers and users (what config works better for my use case?)
> easier.)
>
> I am fine with the suggestion to drive the Gen11 part first, which
> removes the need for any of this.
>
> Patch series is already (AFAIR) nicely split so only the last patch
> needs to be dropped.
>
> If at some point we decide to revisit the Gen8/9 story, we can
> evaluate/measure whether any master switch is actually warranted. I
> think Lionel did some micro-benchmarking which showed impact is not
> so
> severe, so perhaps for real-world use cases it would be even less.
>
> I can re-read the public patches and review them, or perhaps even
> adopt
> them if they have been orphaned. Have to check with Francesco first
> before I commit to the latter.
Thank you for volunteering:).
I talked with Lionel about that and he thinks he may be able to do a
respin next week. So, please, check with him also to avoid double work.
>
> On the uAPI front interface looked fine to me.
>
> One recent interesting development are Mesa patches posted to mesa-
> dev
> (https://lists.freedesktop.org/archives/mesa-dev/2018-July/200607.htm
> l)
> which add EGL_CONTEXT_load_type extension (low/medium/high). This
> would
> need some sort of mapping between low/medium/high to more specific
> settings but still seems okay to me.
>
> This may bring another (open source?) user for the patches. Which
> Gen's
> they are interested in is also a question.
>
> Regards,
>
> Tvrtko
>
> On 24/07/2018 22:50, Bloomfield, Jon wrote:
> > Gratuitous top posting to re-kick the thread.
> >
> > For Gen11 we can't have an on/off switch anyway (media simply won't
> > run
> > with an oncompatible slice config), so let's agree on an api to
> > allow userland
> > to select the slice configuration for its contexts, for Gen11 only.
> > I'd prefer a
> > simple {MediaConfig/GeneralConfig} type context param but I really
> > don't
> > care that much.
> >
> > For gen9/10 it's arguable whether we need this at all. The effect
> > on media
> > workloads varies, but I'm guessing normal users (outside a
> > transcode
> > type environment) will never know they're missing anything. Either
> > way,
> > we can continue discussing while we progress the gen11 solution.
> >
> > Jon
> >
> > > -----Original Message-
> > > From: Intel-gfx On
> > > Behalf Of
> > > Bloomfield, Jon
> > > Sent: Wednesday, July 18, 2018 9:44 AM
> > > To: Tvrtko Ursulin ; Joonas
> > > Lahtinen
> > > ; Chris Wilson > > on.co.uk>;
> > > Landwerlin, Lionel G ; intel-
> > > g...@lists.freedesktop.org
> > > Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs
> > > entry to let users
> > > set sseu configs
> > >
> > > > -Original Message-
> > > > From: Intel-gfx On
> > > > Behalf Of
> > > > Tvrtko Ursulin
> > > > Sent: Thursday, June 14, 2018 1:29 AM
> > > > To: Joonas Lahtinen ; Chris
> > > > Wilson
> > > > ; Landwerlin, Lionel G
> > > > ; intel-...@lists.freedesktop.or
> > > > g
> > > > Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs
> > > > entry to let
> > >
> > > users
> > > > set sseu configs
> > > >
> > > >
> > > > On 13/06/2018 13:49, Joonas Lahtinen wrote:
> > > > > Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
> > > > > >
> > > > > > On 12/06/2018 11:52, Lionel Land
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
[Picking this point in the thread to reply on some points mentioned by
folks in the whole thread.]
I don't remember if any patches from Lionel's series actually had r-b's,
but a few people including myself have certainly been reviewing them. If
I had applied the final r-b I wouldn't have made much difference due
lack of userspace and disagreement on the DoS mitigation story. So to
say effectively put your money where your mouth is and review is not
entirely fair.
Suggestion to add a master sysfs switch was to alleviate the DoS
concerns because dynamic switching has a cost towards all GPU clients,
not that it just has potential to slow down media.
Suggestion was also that this switch becomes immutable and defaults to
"allow" on Gen11 onwards.
I preferred sysfs versus a modparam since it makes testing (Both for
developers and users (what config works better for my use case?) easier.)
I am fine with the suggestion to drive the Gen11 part first, which
removes the need for any of this.
Patch series is already (AFAIR) nicely split so only the last patch
needs to be dropped.
If at some point we decide to revisit the Gen8/9 story, we can
evaluate/measure whether any master switch is actually warranted. I
think Lionel did some micro-benchmarking which showed impact is not so
severe, so perhaps for real-world use cases it would be even less.
I can re-read the public patches and review them, or perhaps even adopt
them if they have been orphaned. Have to check with Francesco first
before I commit to the latter.
On the uAPI front interface looked fine to me.
One recent interesting development are Mesa patches posted to mesa-dev
(https://lists.freedesktop.org/archives/mesa-dev/2018-July/200607.html)
which add EGL_CONTEXT_load_type extension (low/medium/high). This would
need some sort of mapping between low/medium/high to more specific
settings but still seems okay to me.
This may bring another (open source?) user for the patches. Which Gen's
they are interested in is also a question.
Regards,
Tvrtko
On 24/07/2018 22:50, Bloomfield, Jon wrote:
Gratuitous top posting to re-kick the thread.
For Gen11 we can't have an on/off switch anyway (media simply won't run
with an oncompatible slice config), so let's agree on an api to allow userland
to select the slice configuration for its contexts, for Gen11 only. I'd prefer a
simple {MediaConfig/GeneralConfig} type context param but I really don't
care that much.
For gen9/10 it's arguable whether we need this at all. The effect on media
workloads varies, but I'm guessing normal users (outside a transcode
type environment) will never know they're missing anything. Either way,
we can continue discussing while we progress the gen11 solution.
Jon
-Original Message-
From: Intel-gfx On Behalf Of
Bloomfield, Jon
Sent: Wednesday, July 18, 2018 9:44 AM
To: Tvrtko Ursulin ; Joonas Lahtinen
; Chris Wilson ;
Landwerlin, Lionel G ; intel-
g...@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users
set sseu configs
-Original Message-
From: Intel-gfx On Behalf Of
Tvrtko Ursulin
Sent: Thursday, June 14, 2018 1:29 AM
To: Joonas Lahtinen ; Chris Wilson
; Landwerlin, Lionel G
; intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let
users
set sseu configs
On 13/06/2018 13:49, Joonas Lahtinen wrote:
Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
On 12/06/2018 11:52, Lionel Landwerlin wrote:
On 12/06/18 11:37, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-06-12 11:33:34)
On 12/06/18 10:20, Joonas Lahtinen wrote:
Quoting Chris Wilson (2018-06-11 18:02:37)
Quoting Lionel Landwerlin (2018-06-11 14:46:07)
On 11/06/18 13:10, Tvrtko Ursulin wrote:
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per
context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes
adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers
wouldn't
be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on
the
feature, some containers would potentially start negatively
affecting
the others (via the accumulated cost of slice re-configuration
on
context switching).
I am not familiar with typical container setups to be
authoritative
here, but intuitively I find it reasonable that a low-level
hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the
container
environment, make sure your system administrator enables
this
hardware
feature.", "Note to system administrators: Enabling this
features
may
negatively affect
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On Tue, 2018-07-24 at 21:50 +, Bloomfield, Jon wrote:
> Gratuitous top posting to re-kick the thread.
>
> For Gen11 we can't have an on/off switch anyway (media simply won't
> run
> with an oncompatible slice config), so let's agree on an api to allow
> userland
> to select the slice configuration for its contexts, for Gen11 only.
> I'd prefer a
> simple {MediaConfig/GeneralConfig} type context param but I really
> don't
> care that much.
Does anyone work on breaking the patch series for Gen11 and Gen8/9/10
with Gen11 preceding since this is required for the functional side? We
hope to have userspace media driver ICL patches available pretty soon
and would be really nice to have kernel side prepared as much as
possible... If no one is working on this, can you, Lionel, help,
please?
>
> For gen9/10 it's arguable whether we need this at all. The effect on
> media
> workloads varies, but I'm guessing normal users (outside a transcode
> type environment) will never know they're missing anything. Either
> way,
> we can continue discussing while we progress the gen11 solution.
>
> Jon
>
> > -Original Message-
> > From: Intel-gfx On Behalf
> > Of
> > Bloomfield, Jon
> > Sent: Wednesday, July 18, 2018 9:44 AM
> > To: Tvrtko Ursulin ; Joonas
> > Lahtinen
> > ; Chris Wilson > .co.uk>;
> > Landwerlin, Lionel G ; intel-
> > g...@lists.freedesktop.org
> > Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry
> > to let users
> > set sseu configs
> >
> > > -Original Message-
> > > From: Intel-gfx On
> > > Behalf Of
> > > Tvrtko Ursulin
> > > Sent: Thursday, June 14, 2018 1:29 AM
> > > To: Joonas Lahtinen ; Chris
> > > Wilson
> > > ; Landwerlin, Lionel G
> > > ; intel-gfx@lists.freedesktop.org
> > > Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs
> > > entry to let
> >
> > users
> > > set sseu configs
> > >
> > >
> > > On 13/06/2018 13:49, Joonas Lahtinen wrote:
> > > > Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
> > > > >
> > > > > On 12/06/2018 11:52, Lionel Landwerlin wrote:
> > > > > > On 12/06/18 11:37, Chris Wilson wrote:
> > > > > > > Quoting Lionel Landwerlin (2018-06-12 11:33:34)
> > > > > > > > On 12/06/18 10:20, Joonas Lahtinen wrote:
> > > > > > > > > Quoting Chris Wilson (2018-06-11 18:02:37)
> > > > > > > > > > Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> > > > > > > > > > > On 11/06/18 13:10, Tvrtko Ursulin wrote:
> > > > > > > > > > > > On 30/05/2018 15:33, Lionel Landwerlin wrote:
> > > > > > > > > > > > > There are concerns about denial of service
> > > > > > > > > > > > > around the per
> > > > > > > > > > > > > context sseu
> > > > > > > > > > > > > configuration capability. In a previous
> > > > > > > > > > > > > commit introducing the
> > > > > > > > > > > > > capability we allowed it only for capable
> > > > > > > > > > > > > users. This changes
> > > > > > > > > > > > > adds a
> > > > > > > > > > > > > new debugfs entry to let any user configure
> > > > > > > > > > > > > its own context
> > > > > > > > > > > > > powergating setup.
> > > > > > > > > > > >
> > > > > > > > > > > > As far as I understood it, Joonas' concerns
> > > > > > > > > > > > here are:
> > > > > > > > > > > >
> > > > > > > > > > > > 1) That in the containers use case individual
> > > > > > > > > > > > containers
> >
> > wouldn't
> > > be
> > > > > > > > > > > > able to turn on the sysfs toggle for them.
> > > > > > > > > > > >
> > > > > > > > > > > > 2) That also in the containers use case if box
> > > > > > > > > > > > admin turns on
> >
> > the
> > > > > > > > > > > > feature, some conta
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Gratuitous top posting to re-kick the thread.
For Gen11 we can't have an on/off switch anyway (media simply won't run
with an oncompatible slice config), so let's agree on an api to allow userland
to select the slice configuration for its contexts, for Gen11 only. I'd prefer a
simple {MediaConfig/GeneralConfig} type context param but I really don't
care that much.
For gen9/10 it's arguable whether we need this at all. The effect on media
workloads varies, but I'm guessing normal users (outside a transcode
type environment) will never know they're missing anything. Either way,
we can continue discussing while we progress the gen11 solution.
Jon
> -Original Message-
> From: Intel-gfx On Behalf Of
> Bloomfield, Jon
> Sent: Wednesday, July 18, 2018 9:44 AM
> To: Tvrtko Ursulin ; Joonas Lahtinen
> ; Chris Wilson ;
> Landwerlin, Lionel G ; intel-
> g...@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let
> users
> set sseu configs
>
> > -Original Message-
> > From: Intel-gfx On Behalf Of
> > Tvrtko Ursulin
> > Sent: Thursday, June 14, 2018 1:29 AM
> > To: Joonas Lahtinen ; Chris Wilson
> > ; Landwerlin, Lionel G
> > ; intel-gfx@lists.freedesktop.org
> > Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let
> users
> > set sseu configs
> >
> >
> > On 13/06/2018 13:49, Joonas Lahtinen wrote:
> > > Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
> > >>
> > >> On 12/06/2018 11:52, Lionel Landwerlin wrote:
> > >>> On 12/06/18 11:37, Chris Wilson wrote:
> > >>>> Quoting Lionel Landwerlin (2018-06-12 11:33:34)
> > >>>>> On 12/06/18 10:20, Joonas Lahtinen wrote:
> > >>>>>> Quoting Chris Wilson (2018-06-11 18:02:37)
> > >>>>>>> Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> > >>>>>>>> On 11/06/18 13:10, Tvrtko Ursulin wrote:
> > >>>>>>>>> On 30/05/2018 15:33, Lionel Landwerlin wrote:
> > >>>>>>>>>> There are concerns about denial of service around the per
> > >>>>>>>>>> context sseu
> > >>>>>>>>>> configuration capability. In a previous commit introducing the
> > >>>>>>>>>> capability we allowed it only for capable users. This changes
> > >>>>>>>>>> adds a
> > >>>>>>>>>> new debugfs entry to let any user configure its own context
> > >>>>>>>>>> powergating setup.
> > >>>>>>>>> As far as I understood it, Joonas' concerns here are:
> > >>>>>>>>>
> > >>>>>>>>> 1) That in the containers use case individual containers
> wouldn't
> > be
> > >>>>>>>>> able to turn on the sysfs toggle for them.
> > >>>>>>>>>
> > >>>>>>>>> 2) That also in the containers use case if box admin turns on
> the
> > >>>>>>>>> feature, some containers would potentially start negatively
> > >>>>>>>>> affecting
> > >>>>>>>>> the others (via the accumulated cost of slice re-configuration
> on
> > >>>>>>>>> context switching).
> > >>>>>>>>>
> > >>>>>>>>> I am not familiar with typical container setups to be
> authoritative
> > >>>>>>>>> here, but intuitively I find it reasonable that a low-level
> hardware
> > >>>>>>>>> switch like this would be under the control of a master domain
> > >>>>>>>>> administrator. ("If you are installing our product in the
> container
> > >>>>>>>>> environment, make sure your system administrator enables
> this
> > >>>>>>>>> hardware
> > >>>>>>>>> feature.", "Note to system administrators: Enabling this
> features
> > >>>>>>>>> may
> > >>>>>>>>> negatively affect the performance of other containers.")
> > >>>>>>>>>
> > >>>>>>>>> Alternative proposal is for the i915 to apply an "or" filter on
> > >>>>>>>>> all
> > >>>>>>>>> requested masks and
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Quoting Bloomfield, Jon (2018-07-18 19:44:14)
> > -Original Message-
> > From: Intel-gfx On Behalf Of
> > Tvrtko Ursulin
> > Sent: Thursday, June 14, 2018 1:29 AM
> > To: Joonas Lahtinen ; Chris Wilson
> > ; Landwerlin, Lionel G
> > ; intel-gfx@lists.freedesktop.org
> > Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let
> > users
> > set sseu configs
> >
> >
> > On 13/06/2018 13:49, Joonas Lahtinen wrote:
> > > Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
> > >>
> > >> On 12/06/2018 11:52, Lionel Landwerlin wrote:
> > >>> On 12/06/18 11:37, Chris Wilson wrote:
> > >>>> Quoting Lionel Landwerlin (2018-06-12 11:33:34)
> > >>>>> On 12/06/18 10:20, Joonas Lahtinen wrote:
> > >>>>>> Quoting Chris Wilson (2018-06-11 18:02:37)
> > >>>>>>> Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> > >>>>>>>> On 11/06/18 13:10, Tvrtko Ursulin wrote:
> > >>>>>>>>> On 30/05/2018 15:33, Lionel Landwerlin wrote:
> > >>>>>>>>>> There are concerns about denial of service around the per
> > >>>>>>>>>> context sseu
> > >>>>>>>>>> configuration capability. In a previous commit introducing the
> > >>>>>>>>>> capability we allowed it only for capable users. This changes
> > >>>>>>>>>> adds a
> > >>>>>>>>>> new debugfs entry to let any user configure its own context
> > >>>>>>>>>> powergating setup.
> > >>>>>>>>> As far as I understood it, Joonas' concerns here are:
> > >>>>>>>>>
> > >>>>>>>>> 1) That in the containers use case individual containers wouldn't
> > be
> > >>>>>>>>> able to turn on the sysfs toggle for them.
> > >>>>>>>>>
> > >>>>>>>>> 2) That also in the containers use case if box admin turns on the
> > >>>>>>>>> feature, some containers would potentially start negatively
> > >>>>>>>>> affecting
> > >>>>>>>>> the others (via the accumulated cost of slice re-configuration on
> > >>>>>>>>> context switching).
> > >>>>>>>>>
> > >>>>>>>>> I am not familiar with typical container setups to be
> > >>>>>>>>> authoritative
> > >>>>>>>>> here, but intuitively I find it reasonable that a low-level
> > >>>>>>>>> hardware
> > >>>>>>>>> switch like this would be under the control of a master domain
> > >>>>>>>>> administrator. ("If you are installing our product in the
> > >>>>>>>>> container
> > >>>>>>>>> environment, make sure your system administrator enables this
> > >>>>>>>>> hardware
> > >>>>>>>>> feature.", "Note to system administrators: Enabling this features
> > >>>>>>>>> may
> > >>>>>>>>> negatively affect the performance of other containers.")
> > >>>>>>>>>
> > >>>>>>>>> Alternative proposal is for the i915 to apply an "or" filter on
> > >>>>>>>>> all
> > >>>>>>>>> requested masks and in that way ensure dynamic re-
> > configuration
> > >>>>>>>>> doesn't happen on context switches, but driven from userspace
> > via
> > >>>>>>>>> ioctls.
> > >>>>>>>>>
> > >>>>>>>>> In other words, should _all_ userspace agree between
> > themselves that
> > >>>>>>>>> they want to turn off a slice, they would then need to send out a
> > >>>>>>>>> concerted ioctl storm, where number of needed ioctls equals
> > the
> > >>>>>>>>> number
> > >>>>>>>>> of currently active contexts. (This may have its own performance
> > >>>>>>>>> consequences caused by the barr
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
> -Original Message-
> From: Intel-gfx On Behalf Of
> Tvrtko Ursulin
> Sent: Thursday, June 14, 2018 1:29 AM
> To: Joonas Lahtinen ; Chris Wilson
> ; Landwerlin, Lionel G
> ; intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let
> users
> set sseu configs
>
>
> On 13/06/2018 13:49, Joonas Lahtinen wrote:
> > Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
> >>
> >> On 12/06/2018 11:52, Lionel Landwerlin wrote:
> >>> On 12/06/18 11:37, Chris Wilson wrote:
> >>>> Quoting Lionel Landwerlin (2018-06-12 11:33:34)
> >>>>> On 12/06/18 10:20, Joonas Lahtinen wrote:
> >>>>>> Quoting Chris Wilson (2018-06-11 18:02:37)
> >>>>>>> Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> >>>>>>>> On 11/06/18 13:10, Tvrtko Ursulin wrote:
> >>>>>>>>> On 30/05/2018 15:33, Lionel Landwerlin wrote:
> >>>>>>>>>> There are concerns about denial of service around the per
> >>>>>>>>>> context sseu
> >>>>>>>>>> configuration capability. In a previous commit introducing the
> >>>>>>>>>> capability we allowed it only for capable users. This changes
> >>>>>>>>>> adds a
> >>>>>>>>>> new debugfs entry to let any user configure its own context
> >>>>>>>>>> powergating setup.
> >>>>>>>>> As far as I understood it, Joonas' concerns here are:
> >>>>>>>>>
> >>>>>>>>> 1) That in the containers use case individual containers wouldn't
> be
> >>>>>>>>> able to turn on the sysfs toggle for them.
> >>>>>>>>>
> >>>>>>>>> 2) That also in the containers use case if box admin turns on the
> >>>>>>>>> feature, some containers would potentially start negatively
> >>>>>>>>> affecting
> >>>>>>>>> the others (via the accumulated cost of slice re-configuration on
> >>>>>>>>> context switching).
> >>>>>>>>>
> >>>>>>>>> I am not familiar with typical container setups to be authoritative
> >>>>>>>>> here, but intuitively I find it reasonable that a low-level hardware
> >>>>>>>>> switch like this would be under the control of a master domain
> >>>>>>>>> administrator. ("If you are installing our product in the container
> >>>>>>>>> environment, make sure your system administrator enables this
> >>>>>>>>> hardware
> >>>>>>>>> feature.", "Note to system administrators: Enabling this features
> >>>>>>>>> may
> >>>>>>>>> negatively affect the performance of other containers.")
> >>>>>>>>>
> >>>>>>>>> Alternative proposal is for the i915 to apply an "or" filter on all
> >>>>>>>>> requested masks and in that way ensure dynamic re-
> configuration
> >>>>>>>>> doesn't happen on context switches, but driven from userspace
> via
> >>>>>>>>> ioctls.
> >>>>>>>>>
> >>>>>>>>> In other words, should _all_ userspace agree between
> themselves that
> >>>>>>>>> they want to turn off a slice, they would then need to send out a
> >>>>>>>>> concerted ioctl storm, where number of needed ioctls equals
> the
> >>>>>>>>> number
> >>>>>>>>> of currently active contexts. (This may have its own performance
> >>>>>>>>> consequences caused by the barriers needed to modify all
> context
> >>>>>>>>> images.)
> >>>>>>>>>
> >>>>>>>>> This was deemed acceptable the the media use case, but my
> concern is
> >>>>>>>>> the approach is not elegant and will tie us with the "or" policy in
> >>>>>>>>> the ABI. (Performance concerns I haven't evaluated yet, but
> they
> >>>>>>>>> also
> >>>>>>>
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On 13/06/2018 13:49, Joonas Lahtinen wrote:
Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
On 12/06/2018 11:52, Lionel Landwerlin wrote:
On 12/06/18 11:37, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-06-12 11:33:34)
On 12/06/18 10:20, Joonas Lahtinen wrote:
Quoting Chris Wilson (2018-06-11 18:02:37)
Quoting Lionel Landwerlin (2018-06-11 14:46:07)
On 11/06/18 13:10, Tvrtko Ursulin wrote:
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per
context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes
adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers wouldn't be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on the
feature, some containers would potentially start negatively
affecting
the others (via the accumulated cost of slice re-configuration on
context switching).
I am not familiar with typical container setups to be authoritative
here, but intuitively I find it reasonable that a low-level hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the container
environment, make sure your system administrator enables this
hardware
feature.", "Note to system administrators: Enabling this features
may
negatively affect the performance of other containers.")
Alternative proposal is for the i915 to apply an "or" filter on all
requested masks and in that way ensure dynamic re-configuration
doesn't happen on context switches, but driven from userspace via
ioctls.
In other words, should _all_ userspace agree between themselves that
they want to turn off a slice, they would then need to send out a
concerted ioctl storm, where number of needed ioctls equals the
number
of currently active contexts. (This may have its own performance
consequences caused by the barriers needed to modify all context
images.)
This was deemed acceptable the the media use case, but my concern is
the approach is not elegant and will tie us with the "or" policy in
the ABI. (Performance concerns I haven't evaluated yet, but they
also
may be significant.)
If we go back thinking about the containers use case, then it
transpires that even though the "or" policy does prevent one
container
from affecting the other from one angle, it also prevents one
container from exercising the feature unless all containers
co-operate.
As such, we can view the original problem statement where we have an
issue if not everyone co-operates, as conceptually the same just
from
an opposite angle. (Rather than one container incurring the
increased
cost of context switches to the rest, we would have one container
preventing the optimized slice configuration to the other.)
From this follows that both proposals require complete
co-operation
from all running userspace to avoid complete control of the feature.
Since the balance between the benefit of optimized slice
configuration
(or penalty of suboptimal one), versus the penalty of increased
context switch times, cannot be know by the driver (barring
venturing
into the heuristics territory), that is another reason why I find
the
"or" policy in the driver questionable.
We can also ask a question of - If we go with the "or" policy, why
require N per-context ioctls to modify the global GPU configuration
and not instead add a global driver ioctl to modify the state?
If a future hardware requires, or enables, the per-context behaviour
in a more efficient way, we could then revisit the problem space.
In the mean time I see the "or" policy solution as adding some ABI
which doesn't do anything for many use cases without any way for the
sysadmin to enable it. At the same time master sysfs knob at least
enables the sysadmin to make a decision. Here I am thinking about a
random client environment where not all userspace co-operates,
but for
instance user is running the feature aware media stack, and
non-feature aware OpenCL/3d stack.
I guess the complete story boils down to - is the master sysfs knob
really a problem in container use cases.
Regards,
Tvrtko
Hey Tvrtko,
Thanks for summarizing a bunch of discussions.
Essentially I agree with every you wrote above.
If we have a global setting (determined by the OR policy), what's the
point of per context settings?
In Dmitry's scenario, all userspace applications will work
together to
reach the consensus so it sounds like we're reimplementing the policy
that is already existing in userspace.
Anyway, I'm implementing Joonas' suggestion. Hopefully somebody else
than me pick one or the other :)
I'll just mention the voting/consensus approach to see if anyone else
likes it.
Each context has a CONTEXT_PARAM_HINT_SSEU { small, dontcare, large }
(or some
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Quoting Tvrtko Ursulin (2018-06-12 15:02:07)
>
> On 12/06/2018 11:52, Lionel Landwerlin wrote:
> > On 12/06/18 11:37, Chris Wilson wrote:
> >> Quoting Lionel Landwerlin (2018-06-12 11:33:34)
> >>> On 12/06/18 10:20, Joonas Lahtinen wrote:
> Quoting Chris Wilson (2018-06-11 18:02:37)
> > Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> >> On 11/06/18 13:10, Tvrtko Ursulin wrote:
> >>> On 30/05/2018 15:33, Lionel Landwerlin wrote:
> There are concerns about denial of service around the per
> context sseu
> configuration capability. In a previous commit introducing the
> capability we allowed it only for capable users. This changes
> adds a
> new debugfs entry to let any user configure its own context
> powergating setup.
> >>> As far as I understood it, Joonas' concerns here are:
> >>>
> >>> 1) That in the containers use case individual containers wouldn't be
> >>> able to turn on the sysfs toggle for them.
> >>>
> >>> 2) That also in the containers use case if box admin turns on the
> >>> feature, some containers would potentially start negatively
> >>> affecting
> >>> the others (via the accumulated cost of slice re-configuration on
> >>> context switching).
> >>>
> >>> I am not familiar with typical container setups to be authoritative
> >>> here, but intuitively I find it reasonable that a low-level hardware
> >>> switch like this would be under the control of a master domain
> >>> administrator. ("If you are installing our product in the container
> >>> environment, make sure your system administrator enables this
> >>> hardware
> >>> feature.", "Note to system administrators: Enabling this features
> >>> may
> >>> negatively affect the performance of other containers.")
> >>>
> >>> Alternative proposal is for the i915 to apply an "or" filter on all
> >>> requested masks and in that way ensure dynamic re-configuration
> >>> doesn't happen on context switches, but driven from userspace via
> >>> ioctls.
> >>>
> >>> In other words, should _all_ userspace agree between themselves that
> >>> they want to turn off a slice, they would then need to send out a
> >>> concerted ioctl storm, where number of needed ioctls equals the
> >>> number
> >>> of currently active contexts. (This may have its own performance
> >>> consequences caused by the barriers needed to modify all context
> >>> images.)
> >>>
> >>> This was deemed acceptable the the media use case, but my concern is
> >>> the approach is not elegant and will tie us with the "or" policy in
> >>> the ABI. (Performance concerns I haven't evaluated yet, but they
> >>> also
> >>> may be significant.)
> >>>
> >>> If we go back thinking about the containers use case, then it
> >>> transpires that even though the "or" policy does prevent one
> >>> container
> >>> from affecting the other from one angle, it also prevents one
> >>> container from exercising the feature unless all containers
> >>> co-operate.
> >>>
> >>> As such, we can view the original problem statement where we have an
> >>> issue if not everyone co-operates, as conceptually the same just
> >>> from
> >>> an opposite angle. (Rather than one container incurring the
> >>> increased
> >>> cost of context switches to the rest, we would have one container
> >>> preventing the optimized slice configuration to the other.)
> >>>
> >>> From this follows that both proposals require complete
> >>> co-operation
> >>> from all running userspace to avoid complete control of the feature.
> >>>
> >>> Since the balance between the benefit of optimized slice
> >>> configuration
> >>> (or penalty of suboptimal one), versus the penalty of increased
> >>> context switch times, cannot be know by the driver (barring
> >>> venturing
> >>> into the heuristics territory), that is another reason why I find
> >>> the
> >>> "or" policy in the driver questionable.
> >>>
> >>> We can also ask a question of - If we go with the "or" policy, why
> >>> require N per-context ioctls to modify the global GPU configuration
> >>> and not instead add a global driver ioctl to modify the state?
> >>>
> >>> If a future hardware requires, or enables, the per-context behaviour
> >>> in a more efficient way, we could then revisit the problem space.
> >>>
> >>> In the mean time I see the "or" policy solution as adding some ABI
> >>> which doesn't do anything for many use cases without any way for the
> >>> sysadmin to enable it. At the same time master sysfs knob at least
> >>> enables the sysadmin to make a decision. Here I am thinking about a
> >>> random client environment where not all userspace co-operates,
> >>> but
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Quoting Lionel Landwerlin (2018-06-12 11:52:10) > I'm looking forward to the definition of the greater good :) > Tvrtko wanted to avoid the heuristic territory, it seems like we're just > stepping into it. If we have to make any choice, we have not just stepped, but dived head first into it. Tbh, I quite like the idea of having BPF policy hooks. (Devil will definitely be in the details!) -Chris ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On 12/06/2018 11:52, Lionel Landwerlin wrote:
On 12/06/18 11:37, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-06-12 11:33:34)
On 12/06/18 10:20, Joonas Lahtinen wrote:
Quoting Chris Wilson (2018-06-11 18:02:37)
Quoting Lionel Landwerlin (2018-06-11 14:46:07)
On 11/06/18 13:10, Tvrtko Ursulin wrote:
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per
context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes
adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers wouldn't be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on the
feature, some containers would potentially start negatively
affecting
the others (via the accumulated cost of slice re-configuration on
context switching).
I am not familiar with typical container setups to be authoritative
here, but intuitively I find it reasonable that a low-level hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the container
environment, make sure your system administrator enables this
hardware
feature.", "Note to system administrators: Enabling this features
may
negatively affect the performance of other containers.")
Alternative proposal is for the i915 to apply an "or" filter on all
requested masks and in that way ensure dynamic re-configuration
doesn't happen on context switches, but driven from userspace via
ioctls.
In other words, should _all_ userspace agree between themselves that
they want to turn off a slice, they would then need to send out a
concerted ioctl storm, where number of needed ioctls equals the
number
of currently active contexts. (This may have its own performance
consequences caused by the barriers needed to modify all context
images.)
This was deemed acceptable the the media use case, but my concern is
the approach is not elegant and will tie us with the "or" policy in
the ABI. (Performance concerns I haven't evaluated yet, but they
also
may be significant.)
If we go back thinking about the containers use case, then it
transpires that even though the "or" policy does prevent one
container
from affecting the other from one angle, it also prevents one
container from exercising the feature unless all containers
co-operate.
As such, we can view the original problem statement where we have an
issue if not everyone co-operates, as conceptually the same just
from
an opposite angle. (Rather than one container incurring the
increased
cost of context switches to the rest, we would have one container
preventing the optimized slice configuration to the other.)
From this follows that both proposals require complete
co-operation
from all running userspace to avoid complete control of the feature.
Since the balance between the benefit of optimized slice
configuration
(or penalty of suboptimal one), versus the penalty of increased
context switch times, cannot be know by the driver (barring
venturing
into the heuristics territory), that is another reason why I find
the
"or" policy in the driver questionable.
We can also ask a question of - If we go with the "or" policy, why
require N per-context ioctls to modify the global GPU configuration
and not instead add a global driver ioctl to modify the state?
If a future hardware requires, or enables, the per-context behaviour
in a more efficient way, we could then revisit the problem space.
In the mean time I see the "or" policy solution as adding some ABI
which doesn't do anything for many use cases without any way for the
sysadmin to enable it. At the same time master sysfs knob at least
enables the sysadmin to make a decision. Here I am thinking about a
random client environment where not all userspace co-operates,
but for
instance user is running the feature aware media stack, and
non-feature aware OpenCL/3d stack.
I guess the complete story boils down to - is the master sysfs knob
really a problem in container use cases.
Regards,
Tvrtko
Hey Tvrtko,
Thanks for summarizing a bunch of discussions.
Essentially I agree with every you wrote above.
If we have a global setting (determined by the OR policy), what's the
point of per context settings?
In Dmitry's scenario, all userspace applications will work
together to
reach the consensus so it sounds like we're reimplementing the policy
that is already existing in userspace.
Anyway, I'm implementing Joonas' suggestion. Hopefully somebody else
than me pick one or the other :)
I'll just mention the voting/consensus approach to see if anyone else
likes it.
Each context has a CONTEXT_PARAM_HINT_SSEU { small, dontcare, large }
(or some other abstract names).
Yeah, the param name should have the
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On 12/06/18 11:37, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-06-12 11:33:34)
On 12/06/18 10:20, Joonas Lahtinen wrote:
Quoting Chris Wilson (2018-06-11 18:02:37)
Quoting Lionel Landwerlin (2018-06-11 14:46:07)
On 11/06/18 13:10, Tvrtko Ursulin wrote:
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers wouldn't be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on the
feature, some containers would potentially start negatively affecting
the others (via the accumulated cost of slice re-configuration on
context switching).
I am not familiar with typical container setups to be authoritative
here, but intuitively I find it reasonable that a low-level hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the container
environment, make sure your system administrator enables this hardware
feature.", "Note to system administrators: Enabling this features may
negatively affect the performance of other containers.")
Alternative proposal is for the i915 to apply an "or" filter on all
requested masks and in that way ensure dynamic re-configuration
doesn't happen on context switches, but driven from userspace via ioctls.
In other words, should _all_ userspace agree between themselves that
they want to turn off a slice, they would then need to send out a
concerted ioctl storm, where number of needed ioctls equals the number
of currently active contexts. (This may have its own performance
consequences caused by the barriers needed to modify all context images.)
This was deemed acceptable the the media use case, but my concern is
the approach is not elegant and will tie us with the "or" policy in
the ABI. (Performance concerns I haven't evaluated yet, but they also
may be significant.)
If we go back thinking about the containers use case, then it
transpires that even though the "or" policy does prevent one container
from affecting the other from one angle, it also prevents one
container from exercising the feature unless all containers co-operate.
As such, we can view the original problem statement where we have an
issue if not everyone co-operates, as conceptually the same just from
an opposite angle. (Rather than one container incurring the increased
cost of context switches to the rest, we would have one container
preventing the optimized slice configuration to the other.)
From this follows that both proposals require complete co-operation
from all running userspace to avoid complete control of the feature.
Since the balance between the benefit of optimized slice configuration
(or penalty of suboptimal one), versus the penalty of increased
context switch times, cannot be know by the driver (barring venturing
into the heuristics territory), that is another reason why I find the
"or" policy in the driver questionable.
We can also ask a question of - If we go with the "or" policy, why
require N per-context ioctls to modify the global GPU configuration
and not instead add a global driver ioctl to modify the state?
If a future hardware requires, or enables, the per-context behaviour
in a more efficient way, we could then revisit the problem space.
In the mean time I see the "or" policy solution as adding some ABI
which doesn't do anything for many use cases without any way for the
sysadmin to enable it. At the same time master sysfs knob at least
enables the sysadmin to make a decision. Here I am thinking about a
random client environment where not all userspace co-operates, but for
instance user is running the feature aware media stack, and
non-feature aware OpenCL/3d stack.
I guess the complete story boils down to - is the master sysfs knob
really a problem in container use cases.
Regards,
Tvrtko
Hey Tvrtko,
Thanks for summarizing a bunch of discussions.
Essentially I agree with every you wrote above.
If we have a global setting (determined by the OR policy), what's the
point of per context settings?
In Dmitry's scenario, all userspace applications will work together to
reach the consensus so it sounds like we're reimplementing the policy
that is already existing in userspace.
Anyway, I'm implementing Joonas' suggestion. Hopefully somebody else
than me pick one or the other :)
I'll just mention the voting/consensus approach to see if anyone else
likes it.
Each context has a CONTEXT_PARAM_HINT_SSEU { small, dontcare, large }
(or some other abstract names).
Yeah, the param name should have the word _HINT_ in it when it's not a
definitive set.
There's no global setter across
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Quoting Lionel Landwerlin (2018-06-12 11:33:34)
> On 12/06/18 10:20, Joonas Lahtinen wrote:
> > Quoting Chris Wilson (2018-06-11 18:02:37)
> >> Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> >>> On 11/06/18 13:10, Tvrtko Ursulin wrote:
> On 30/05/2018 15:33, Lionel Landwerlin wrote:
> > There are concerns about denial of service around the per context sseu
> > configuration capability. In a previous commit introducing the
> > capability we allowed it only for capable users. This changes adds a
> > new debugfs entry to let any user configure its own context
> > powergating setup.
> As far as I understood it, Joonas' concerns here are:
>
> 1) That in the containers use case individual containers wouldn't be
> able to turn on the sysfs toggle for them.
>
> 2) That also in the containers use case if box admin turns on the
> feature, some containers would potentially start negatively affecting
> the others (via the accumulated cost of slice re-configuration on
> context switching).
>
> I am not familiar with typical container setups to be authoritative
> here, but intuitively I find it reasonable that a low-level hardware
> switch like this would be under the control of a master domain
> administrator. ("If you are installing our product in the container
> environment, make sure your system administrator enables this hardware
> feature.", "Note to system administrators: Enabling this features may
> negatively affect the performance of other containers.")
>
> Alternative proposal is for the i915 to apply an "or" filter on all
> requested masks and in that way ensure dynamic re-configuration
> doesn't happen on context switches, but driven from userspace via ioctls.
>
> In other words, should _all_ userspace agree between themselves that
> they want to turn off a slice, they would then need to send out a
> concerted ioctl storm, where number of needed ioctls equals the number
> of currently active contexts. (This may have its own performance
> consequences caused by the barriers needed to modify all context images.)
>
> This was deemed acceptable the the media use case, but my concern is
> the approach is not elegant and will tie us with the "or" policy in
> the ABI. (Performance concerns I haven't evaluated yet, but they also
> may be significant.)
>
> If we go back thinking about the containers use case, then it
> transpires that even though the "or" policy does prevent one container
> from affecting the other from one angle, it also prevents one
> container from exercising the feature unless all containers co-operate.
>
> As such, we can view the original problem statement where we have an
> issue if not everyone co-operates, as conceptually the same just from
> an opposite angle. (Rather than one container incurring the increased
> cost of context switches to the rest, we would have one container
> preventing the optimized slice configuration to the other.)
>
> From this follows that both proposals require complete co-operation
> from all running userspace to avoid complete control of the feature.
>
> Since the balance between the benefit of optimized slice configuration
> (or penalty of suboptimal one), versus the penalty of increased
> context switch times, cannot be know by the driver (barring venturing
> into the heuristics territory), that is another reason why I find the
> "or" policy in the driver questionable.
>
> We can also ask a question of - If we go with the "or" policy, why
> require N per-context ioctls to modify the global GPU configuration
> and not instead add a global driver ioctl to modify the state?
>
> If a future hardware requires, or enables, the per-context behaviour
> in a more efficient way, we could then revisit the problem space.
>
> In the mean time I see the "or" policy solution as adding some ABI
> which doesn't do anything for many use cases without any way for the
> sysadmin to enable it. At the same time master sysfs knob at least
> enables the sysadmin to make a decision. Here I am thinking about a
> random client environment where not all userspace co-operates, but for
> instance user is running the feature aware media stack, and
> non-feature aware OpenCL/3d stack.
>
> I guess the complete story boils down to - is the master sysfs knob
> really a problem in container use cases.
>
> Regards,
>
> Tvrtko
> >>> Hey Tvrtko,
> >>>
> >>> Thanks for summarizing a bunch of discussions.
> >>> Essentially I agree with every you wrote above.
> >>>
> >>> If we have a global setting (determined by the OR policy), what's the
> >>> point of per context settings?
> >>>
> >>> In Dmitry's scenario,
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On 12/06/18 10:20, Joonas Lahtinen wrote:
Quoting Chris Wilson (2018-06-11 18:02:37)
Quoting Lionel Landwerlin (2018-06-11 14:46:07)
On 11/06/18 13:10, Tvrtko Ursulin wrote:
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers wouldn't be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on the
feature, some containers would potentially start negatively affecting
the others (via the accumulated cost of slice re-configuration on
context switching).
I am not familiar with typical container setups to be authoritative
here, but intuitively I find it reasonable that a low-level hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the container
environment, make sure your system administrator enables this hardware
feature.", "Note to system administrators: Enabling this features may
negatively affect the performance of other containers.")
Alternative proposal is for the i915 to apply an "or" filter on all
requested masks and in that way ensure dynamic re-configuration
doesn't happen on context switches, but driven from userspace via ioctls.
In other words, should _all_ userspace agree between themselves that
they want to turn off a slice, they would then need to send out a
concerted ioctl storm, where number of needed ioctls equals the number
of currently active contexts. (This may have its own performance
consequences caused by the barriers needed to modify all context images.)
This was deemed acceptable the the media use case, but my concern is
the approach is not elegant and will tie us with the "or" policy in
the ABI. (Performance concerns I haven't evaluated yet, but they also
may be significant.)
If we go back thinking about the containers use case, then it
transpires that even though the "or" policy does prevent one container
from affecting the other from one angle, it also prevents one
container from exercising the feature unless all containers co-operate.
As such, we can view the original problem statement where we have an
issue if not everyone co-operates, as conceptually the same just from
an opposite angle. (Rather than one container incurring the increased
cost of context switches to the rest, we would have one container
preventing the optimized slice configuration to the other.)
From this follows that both proposals require complete co-operation
from all running userspace to avoid complete control of the feature.
Since the balance between the benefit of optimized slice configuration
(or penalty of suboptimal one), versus the penalty of increased
context switch times, cannot be know by the driver (barring venturing
into the heuristics territory), that is another reason why I find the
"or" policy in the driver questionable.
We can also ask a question of - If we go with the "or" policy, why
require N per-context ioctls to modify the global GPU configuration
and not instead add a global driver ioctl to modify the state?
If a future hardware requires, or enables, the per-context behaviour
in a more efficient way, we could then revisit the problem space.
In the mean time I see the "or" policy solution as adding some ABI
which doesn't do anything for many use cases without any way for the
sysadmin to enable it. At the same time master sysfs knob at least
enables the sysadmin to make a decision. Here I am thinking about a
random client environment where not all userspace co-operates, but for
instance user is running the feature aware media stack, and
non-feature aware OpenCL/3d stack.
I guess the complete story boils down to - is the master sysfs knob
really a problem in container use cases.
Regards,
Tvrtko
Hey Tvrtko,
Thanks for summarizing a bunch of discussions.
Essentially I agree with every you wrote above.
If we have a global setting (determined by the OR policy), what's the
point of per context settings?
In Dmitry's scenario, all userspace applications will work together to
reach the consensus so it sounds like we're reimplementing the policy
that is already existing in userspace.
Anyway, I'm implementing Joonas' suggestion. Hopefully somebody else
than me pick one or the other :)
I'll just mention the voting/consensus approach to see if anyone else
likes it.
Each context has a CONTEXT_PARAM_HINT_SSEU { small, dontcare, large }
(or some other abstract names).
Yeah, the param name should have the word _HINT_ in it when it's not a
definitive set.
There's no global setter across containers, only a scenario when
everyone agrees or not. Tallying up the votes and going
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Quoting Chris Wilson (2018-06-11 18:02:37)
> Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> > On 11/06/18 13:10, Tvrtko Ursulin wrote:
> > >
> > > On 30/05/2018 15:33, Lionel Landwerlin wrote:
> > >> There are concerns about denial of service around the per context sseu
> > >> configuration capability. In a previous commit introducing the
> > >> capability we allowed it only for capable users. This changes adds a
> > >> new debugfs entry to let any user configure its own context
> > >> powergating setup.
> > >
> > > As far as I understood it, Joonas' concerns here are:
> > >
> > > 1) That in the containers use case individual containers wouldn't be
> > > able to turn on the sysfs toggle for them.
> > >
> > > 2) That also in the containers use case if box admin turns on the
> > > feature, some containers would potentially start negatively affecting
> > > the others (via the accumulated cost of slice re-configuration on
> > > context switching).
> > >
> > > I am not familiar with typical container setups to be authoritative
> > > here, but intuitively I find it reasonable that a low-level hardware
> > > switch like this would be under the control of a master domain
> > > administrator. ("If you are installing our product in the container
> > > environment, make sure your system administrator enables this hardware
> > > feature.", "Note to system administrators: Enabling this features may
> > > negatively affect the performance of other containers.")
> > >
> > > Alternative proposal is for the i915 to apply an "or" filter on all
> > > requested masks and in that way ensure dynamic re-configuration
> > > doesn't happen on context switches, but driven from userspace via ioctls.
> > >
> > > In other words, should _all_ userspace agree between themselves that
> > > they want to turn off a slice, they would then need to send out a
> > > concerted ioctl storm, where number of needed ioctls equals the number
> > > of currently active contexts. (This may have its own performance
> > > consequences caused by the barriers needed to modify all context images.)
> > >
> > > This was deemed acceptable the the media use case, but my concern is
> > > the approach is not elegant and will tie us with the "or" policy in
> > > the ABI. (Performance concerns I haven't evaluated yet, but they also
> > > may be significant.)
> > >
> > > If we go back thinking about the containers use case, then it
> > > transpires that even though the "or" policy does prevent one container
> > > from affecting the other from one angle, it also prevents one
> > > container from exercising the feature unless all containers co-operate.
> > >
> > > As such, we can view the original problem statement where we have an
> > > issue if not everyone co-operates, as conceptually the same just from
> > > an opposite angle. (Rather than one container incurring the increased
> > > cost of context switches to the rest, we would have one container
> > > preventing the optimized slice configuration to the other.)
> > >
> > > From this follows that both proposals require complete co-operation
> > > from all running userspace to avoid complete control of the feature.
> > >
> > > Since the balance between the benefit of optimized slice configuration
> > > (or penalty of suboptimal one), versus the penalty of increased
> > > context switch times, cannot be know by the driver (barring venturing
> > > into the heuristics territory), that is another reason why I find the
> > > "or" policy in the driver questionable.
> > >
> > > We can also ask a question of - If we go with the "or" policy, why
> > > require N per-context ioctls to modify the global GPU configuration
> > > and not instead add a global driver ioctl to modify the state?
> > >
> > > If a future hardware requires, or enables, the per-context behaviour
> > > in a more efficient way, we could then revisit the problem space.
> > >
> > > In the mean time I see the "or" policy solution as adding some ABI
> > > which doesn't do anything for many use cases without any way for the
> > > sysadmin to enable it. At the same time master sysfs knob at least
> > > enables the sysadmin to make a decision. Here I am thinking about a
> > > random client environment where not all userspace co-operates, but for
> > > instance user is running the feature aware media stack, and
> > > non-feature aware OpenCL/3d stack.
> > >
> > > I guess the complete story boils down to - is the master sysfs knob
> > > really a problem in container use cases.
> > >
> > > Regards,
> > >
> > > Tvrtko
> >
> > Hey Tvrtko,
> >
> > Thanks for summarizing a bunch of discussions.
> > Essentially I agree with every you wrote above.
> >
> > If we have a global setting (determined by the OR policy), what's the
> > point of per context settings?
> >
> > In Dmitry's scenario, all userspace applications will work together to
> > reach the consensus so it sounds like we're reimplementing the policy
> > that is
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
Quoting Lionel Landwerlin (2018-06-11 14:46:07)
> On 11/06/18 13:10, Tvrtko Ursulin wrote:
> >
> > On 30/05/2018 15:33, Lionel Landwerlin wrote:
> >> There are concerns about denial of service around the per context sseu
> >> configuration capability. In a previous commit introducing the
> >> capability we allowed it only for capable users. This changes adds a
> >> new debugfs entry to let any user configure its own context
> >> powergating setup.
> >
> > As far as I understood it, Joonas' concerns here are:
> >
> > 1) That in the containers use case individual containers wouldn't be
> > able to turn on the sysfs toggle for them.
> >
> > 2) That also in the containers use case if box admin turns on the
> > feature, some containers would potentially start negatively affecting
> > the others (via the accumulated cost of slice re-configuration on
> > context switching).
> >
> > I am not familiar with typical container setups to be authoritative
> > here, but intuitively I find it reasonable that a low-level hardware
> > switch like this would be under the control of a master domain
> > administrator. ("If you are installing our product in the container
> > environment, make sure your system administrator enables this hardware
> > feature.", "Note to system administrators: Enabling this features may
> > negatively affect the performance of other containers.")
> >
> > Alternative proposal is for the i915 to apply an "or" filter on all
> > requested masks and in that way ensure dynamic re-configuration
> > doesn't happen on context switches, but driven from userspace via ioctls.
> >
> > In other words, should _all_ userspace agree between themselves that
> > they want to turn off a slice, they would then need to send out a
> > concerted ioctl storm, where number of needed ioctls equals the number
> > of currently active contexts. (This may have its own performance
> > consequences caused by the barriers needed to modify all context images.)
> >
> > This was deemed acceptable the the media use case, but my concern is
> > the approach is not elegant and will tie us with the "or" policy in
> > the ABI. (Performance concerns I haven't evaluated yet, but they also
> > may be significant.)
> >
> > If we go back thinking about the containers use case, then it
> > transpires that even though the "or" policy does prevent one container
> > from affecting the other from one angle, it also prevents one
> > container from exercising the feature unless all containers co-operate.
> >
> > As such, we can view the original problem statement where we have an
> > issue if not everyone co-operates, as conceptually the same just from
> > an opposite angle. (Rather than one container incurring the increased
> > cost of context switches to the rest, we would have one container
> > preventing the optimized slice configuration to the other.)
> >
> > From this follows that both proposals require complete co-operation
> > from all running userspace to avoid complete control of the feature.
> >
> > Since the balance between the benefit of optimized slice configuration
> > (or penalty of suboptimal one), versus the penalty of increased
> > context switch times, cannot be know by the driver (barring venturing
> > into the heuristics territory), that is another reason why I find the
> > "or" policy in the driver questionable.
> >
> > We can also ask a question of - If we go with the "or" policy, why
> > require N per-context ioctls to modify the global GPU configuration
> > and not instead add a global driver ioctl to modify the state?
> >
> > If a future hardware requires, or enables, the per-context behaviour
> > in a more efficient way, we could then revisit the problem space.
> >
> > In the mean time I see the "or" policy solution as adding some ABI
> > which doesn't do anything for many use cases without any way for the
> > sysadmin to enable it. At the same time master sysfs knob at least
> > enables the sysadmin to make a decision. Here I am thinking about a
> > random client environment where not all userspace co-operates, but for
> > instance user is running the feature aware media stack, and
> > non-feature aware OpenCL/3d stack.
> >
> > I guess the complete story boils down to - is the master sysfs knob
> > really a problem in container use cases.
> >
> > Regards,
> >
> > Tvrtko
>
> Hey Tvrtko,
>
> Thanks for summarizing a bunch of discussions.
> Essentially I agree with every you wrote above.
>
> If we have a global setting (determined by the OR policy), what's the
> point of per context settings?
>
> In Dmitry's scenario, all userspace applications will work together to
> reach the consensus so it sounds like we're reimplementing the policy
> that is already existing in userspace.
>
> Anyway, I'm implementing Joonas' suggestion. Hopefully somebody else
> than me pick one or the other :)
I'll just mention the voting/consensus approach to see if anyone else
likes it.
Each
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On 11/06/18 13:10, Tvrtko Ursulin wrote:
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers wouldn't be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on the
feature, some containers would potentially start negatively affecting
the others (via the accumulated cost of slice re-configuration on
context switching).
I am not familiar with typical container setups to be authoritative
here, but intuitively I find it reasonable that a low-level hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the container
environment, make sure your system administrator enables this hardware
feature.", "Note to system administrators: Enabling this features may
negatively affect the performance of other containers.")
Alternative proposal is for the i915 to apply an "or" filter on all
requested masks and in that way ensure dynamic re-configuration
doesn't happen on context switches, but driven from userspace via ioctls.
In other words, should _all_ userspace agree between themselves that
they want to turn off a slice, they would then need to send out a
concerted ioctl storm, where number of needed ioctls equals the number
of currently active contexts. (This may have its own performance
consequences caused by the barriers needed to modify all context images.)
This was deemed acceptable the the media use case, but my concern is
the approach is not elegant and will tie us with the "or" policy in
the ABI. (Performance concerns I haven't evaluated yet, but they also
may be significant.)
If we go back thinking about the containers use case, then it
transpires that even though the "or" policy does prevent one container
from affecting the other from one angle, it also prevents one
container from exercising the feature unless all containers co-operate.
As such, we can view the original problem statement where we have an
issue if not everyone co-operates, as conceptually the same just from
an opposite angle. (Rather than one container incurring the increased
cost of context switches to the rest, we would have one container
preventing the optimized slice configuration to the other.)
From this follows that both proposals require complete co-operation
from all running userspace to avoid complete control of the feature.
Since the balance between the benefit of optimized slice configuration
(or penalty of suboptimal one), versus the penalty of increased
context switch times, cannot be know by the driver (barring venturing
into the heuristics territory), that is another reason why I find the
"or" policy in the driver questionable.
We can also ask a question of - If we go with the "or" policy, why
require N per-context ioctls to modify the global GPU configuration
and not instead add a global driver ioctl to modify the state?
If a future hardware requires, or enables, the per-context behaviour
in a more efficient way, we could then revisit the problem space.
In the mean time I see the "or" policy solution as adding some ABI
which doesn't do anything for many use cases without any way for the
sysadmin to enable it. At the same time master sysfs knob at least
enables the sysadmin to make a decision. Here I am thinking about a
random client environment where not all userspace co-operates, but for
instance user is running the feature aware media stack, and
non-feature aware OpenCL/3d stack.
I guess the complete story boils down to - is the master sysfs knob
really a problem in container use cases.
Regards,
Tvrtko
Hey Tvrtko,
Thanks for summarizing a bunch of discussions.
Essentially I agree with every you wrote above.
If we have a global setting (determined by the OR policy), what's the
point of per context settings?
In Dmitry's scenario, all userspace applications will work together to
reach the consensus so it sounds like we're reimplementing the policy
that is already existing in userspace.
Anyway, I'm implementing Joonas' suggestion. Hopefully somebody else
than me pick one or the other :)
Cheers,
-
Lionel
___
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
On 30/05/2018 15:33, Lionel Landwerlin wrote:
There are concerns about denial of service around the per context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes adds a
new debugfs entry to let any user configure its own context
powergating setup.
As far as I understood it, Joonas' concerns here are:
1) That in the containers use case individual containers wouldn't be
able to turn on the sysfs toggle for them.
2) That also in the containers use case if box admin turns on the
feature, some containers would potentially start negatively affecting
the others (via the accumulated cost of slice re-configuration on
context switching).
I am not familiar with typical container setups to be authoritative
here, but intuitively I find it reasonable that a low-level hardware
switch like this would be under the control of a master domain
administrator. ("If you are installing our product in the container
environment, make sure your system administrator enables this hardware
feature.", "Note to system administrators: Enabling this features may
negatively affect the performance of other containers.")
Alternative proposal is for the i915 to apply an "or" filter on all
requested masks and in that way ensure dynamic re-configuration doesn't
happen on context switches, but driven from userspace via ioctls.
In other words, should _all_ userspace agree between themselves that
they want to turn off a slice, they would then need to send out a
concerted ioctl storm, where number of needed ioctls equals the number
of currently active contexts. (This may have its own performance
consequences caused by the barriers needed to modify all context images.)
This was deemed acceptable the the media use case, but my concern is the
approach is not elegant and will tie us with the "or" policy in the ABI.
(Performance concerns I haven't evaluated yet, but they also may be
significant.)
If we go back thinking about the containers use case, then it transpires
that even though the "or" policy does prevent one container from
affecting the other from one angle, it also prevents one container from
exercising the feature unless all containers co-operate.
As such, we can view the original problem statement where we have an
issue if not everyone co-operates, as conceptually the same just from an
opposite angle. (Rather than one container incurring the increased cost
of context switches to the rest, we would have one container preventing
the optimized slice configuration to the other.)
From this follows that both proposals require complete co-operation
from all running userspace to avoid complete control of the feature.
Since the balance between the benefit of optimized slice configuration
(or penalty of suboptimal one), versus the penalty of increased context
switch times, cannot be know by the driver (barring venturing into the
heuristics territory), that is another reason why I find the "or" policy
in the driver questionable.
We can also ask a question of - If we go with the "or" policy, why
require N per-context ioctls to modify the global GPU configuration and
not instead add a global driver ioctl to modify the state?
If a future hardware requires, or enables, the per-context behaviour in
a more efficient way, we could then revisit the problem space.
In the mean time I see the "or" policy solution as adding some ABI which
doesn't do anything for many use cases without any way for the sysadmin
to enable it. At the same time master sysfs knob at least enables the
sysadmin to make a decision. Here I am thinking about a random client
environment where not all userspace co-operates, but for instance user
is running the feature aware media stack, and non-feature aware
OpenCL/3d stack.
I guess the complete story boils down to - is the master sysfs knob
really a problem in container use cases.
Regards,
Tvrtko
v2: Rename sysfs entry (Tvrtko)
Lock interruptible the device in sysfs (Tvrtko)
Fix dropped error code in getting dynamic sseu value (Tvrtko)
s/dev_priv/i915/ (Tvrtko)
v3: Drop locked function suffix (Tvrtko)
Signed-off-by: Lionel Landwerlin
---
drivers/gpu/drm/i915/i915_drv.h | 16 +++---
drivers/gpu/drm/i915/i915_gem_context.c | 38 +++
drivers/gpu/drm/i915/i915_sysfs.c | 40 +
3 files changed, 90 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b2386c37437d..5aa96a6650b4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1842,6 +1842,8 @@ struct drm_i915_private {
struct ida hw_ida;
#define MAX_CONTEXT_HW_ID (1<<21) /* exclusive */
#define GEN11_MAX_CONTEXT_HW_ID (1<<11) /* exclusive */
+
+ bool dynamic_sseu;
} contexts;
u32 fdi_rx_config;
@@ -3259,6 +3261,10
[Intel-gfx] [PATCH v9 7/7] drm/i915: add a sysfs entry to let users set sseu configs
There are concerns about denial of service around the per context sseu
configuration capability. In a previous commit introducing the
capability we allowed it only for capable users. This changes adds a
new debugfs entry to let any user configure its own context
powergating setup.
v2: Rename sysfs entry (Tvrtko)
Lock interruptible the device in sysfs (Tvrtko)
Fix dropped error code in getting dynamic sseu value (Tvrtko)
s/dev_priv/i915/ (Tvrtko)
v3: Drop locked function suffix (Tvrtko)
Signed-off-by: Lionel Landwerlin
---
drivers/gpu/drm/i915/i915_drv.h | 16 +++---
drivers/gpu/drm/i915/i915_gem_context.c | 38 +++
drivers/gpu/drm/i915/i915_sysfs.c | 40 +
3 files changed, 90 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b2386c37437d..5aa96a6650b4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1842,6 +1842,8 @@ struct drm_i915_private {
struct ida hw_ida;
#define MAX_CONTEXT_HW_ID (1<<21) /* exclusive */
#define GEN11_MAX_CONTEXT_HW_ID (1<<11) /* exclusive */
+
+ bool dynamic_sseu;
} contexts;
u32 fdi_rx_config;
@@ -3259,6 +3261,10 @@ i915_gem_context_lookup(struct drm_i915_file_private
*file_priv, u32 id)
return ctx;
}
+int i915_gem_contexts_set_dynamic_sseu(struct drm_i915_private *i915,
+ bool allowed);
+bool i915_gem_contexts_get_dynamic_sseu(struct drm_i915_private *i915);
+
int i915_perf_open_ioctl(struct drm_device *dev, void *data,
struct drm_file *file);
int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
@@ -3859,11 +3865,13 @@ intel_engine_prepare_sseu(struct intel_engine_cs
*engine,
struct drm_i915_private *i915 = engine->i915;
/*
-* If i915/perf is active, we want a stable powergating configuration
-* on the system. The most natural configuration to take in that case
-* is the default (i.e maximum the hardware can do).
+* If i915/perf is active or dynamic sseu configuration is not allowed
+* (through sysfs), we want a stable powergating configuration on the
+* system. The most natural configuration to take in that case is the
+* default (i.e maximum the hardware can do).
*/
- return i915->perf.oa.exclusive_stream ?
+ return (i915->perf.oa.exclusive_stream ||
+ !i915->contexts.dynamic_sseu) ?
intel_device_default_sseu(i915) : sseu;
}
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c
b/drivers/gpu/drm/i915/i915_gem_context.c
index 79029815c21f..453bdc976be3 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -1118,6 +1118,44 @@ int i915_gem_context_reset_stats_ioctl(struct drm_device
*dev,
return ret;
}
+int i915_gem_contexts_set_dynamic_sseu(struct drm_i915_private *i915,
+ bool allowed)
+{
+ struct intel_engine_cs *engine = i915->engine[RCS];
+ struct i915_gem_context *ctx;
+ int ret = 0;
+
+ lockdep_assert_held(>drm.struct_mutex);
+
+ if (!engine->emit_rpcs_config)
+ return -ENODEV;
+
+ if (allowed == i915->contexts.dynamic_sseu)
+ return 0;
+
+ i915->contexts.dynamic_sseu = allowed;
+
+ list_for_each_entry(ctx, >contexts.list, link) {
+ struct intel_context *ce = to_intel_context(ctx, engine);
+
+ ret = i915_gem_context_reconfigure_sseu(ctx, engine, ce->sseu);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+bool i915_gem_contexts_get_dynamic_sseu(struct drm_i915_private *i915)
+{
+ struct intel_engine_cs *engine = i915->engine[RCS];
+
+ if (!engine->emit_rpcs_config)
+ return false;
+
+ return i915->contexts.dynamic_sseu;
+}
+
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/mock_context.c"
#include "selftests/i915_gem_context.c"
diff --git a/drivers/gpu/drm/i915/i915_sysfs.c
b/drivers/gpu/drm/i915/i915_sysfs.c
index e5e6f6bb2b05..d895054d245e 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -483,6 +483,44 @@ static ssize_t gt_rp_mhz_show(struct device *kdev, struct
device_attribute *attr
return snprintf(buf, PAGE_SIZE, "%d\n", val);
}
+static ssize_t allow_dynamic_sseu_show(struct device *kdev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct drm_i915_private *i915 = kdev_minor_to_i915(kdev);
+ bool value = i915_gem_contexts_get_dynamic_sseu(i915);
+
+ return snprintf(buf, PAGE_SIZE, "%d\n", value);
+}
+
+static ssize_t allow_dynamic_sseu_store(struct device *kdev,
+
