- On Apr 16, 2018, at 4:58 PM, Mathieu Desnoyers
mathieu.desnoy...@efficios.com wrote:
> - On Apr 16, 2018, at 3:26 PM, Linus Torvalds
> torva...@linux-foundation.org
> wrote:
>
>> On Mon, Apr 16, 2018 at 12:21 PM, Mathieu Desnoyers
>> wrote:
>>>
>>> And I try very hard to avoid being
- On Apr 16, 2018, at 3:26 PM, Linus Torvalds torva...@linux-foundation.org
wrote:
> On Mon, Apr 16, 2018 at 12:21 PM, Mathieu Desnoyers
> wrote:
>>
>> And I try very hard to avoid being told I'm the one breaking
>> user-space. ;-)
>
> You *can't* be breaking user space. User space doesn't
On Mon, Apr 16, 2018 at 12:21 PM, Mathieu Desnoyers
wrote:
>
> And I try very hard to avoid being told I'm the one breaking
> user-space. ;-)
You *can't* be breaking user space. User space doesn't use this yet.
That's actually why I'd like to start with the minimal set - to make
sure we don't in
- On Apr 16, 2018, at 2:39 PM, Linus Torvalds torva...@linux-foundation.org
wrote:
> On Mon, Apr 16, 2018 at 11:35 AM, Mathieu Desnoyers
> wrote:
>> Specifically for single-stepping, the __rseq_table section introduced
>> at user-level will allow newer debuggers and tools which do line and
>
On Mon, Apr 16, 2018 at 11:35 AM, Mathieu Desnoyers
wrote:
> Specifically for single-stepping, the __rseq_table section introduced
> at user-level will allow newer debuggers and tools which do line and
> instruction-level single-stepping to skip over rseq critical sections.
> However, this breaks
- On Apr 14, 2018, at 6:44 PM, Andy Lutomirski l...@amacapital.net wrote:
> On Thu, Apr 12, 2018 at 12:43 PM, Linus Torvalds
> wrote:
>> On Thu, Apr 12, 2018 at 12:27 PM, Mathieu Desnoyers
>> wrote:
>>> The cpu_opv system call executes a vector of operations on behalf of
>>> user-space on a
> Single-stepping is only a subset of the rseq limitations addressed
> by cpu_opv. Anoher major limitation is algorithms requiring data
> migration between per-cpu data structures safely against CPU hotplug,
> and without having to change the cpu affinity mask. This is the case
And how many people
- On Apr 12, 2018, at 4:23 PM, Andi Kleen a...@firstfloor.org wrote:
>> Can we plan on merging just the plain rseq parts *without* this all
>> first, and then see the cpu_opv thing as a "maybe future expansion"
>> part.
>
> That would be the right way to go. I doubt anybody really needs cpu_o
On Thu, Apr 12, 2018 at 12:43 PM, Linus Torvalds
wrote:
> On Thu, Apr 12, 2018 at 12:27 PM, Mathieu Desnoyers
> wrote:
>> The cpu_opv system call executes a vector of operations on behalf of
>> user-space on a specific CPU with preemption disabled. It is inspired
>> by readv() and writev() system
- On Apr 13, 2018, at 12:37 PM, Linus Torvalds
torva...@linux-foundation.org wrote:
> On Fri, Apr 13, 2018 at 5:16 AM, Mathieu Desnoyers
> wrote:
>> The vmalloc space needed by cpu_opv is bound by the number of pages
>> a cpu_opv call can touch.
>
> No it's not.
>
> You can have a thousand
On Fri, Apr 13, 2018 at 5:16 AM, Mathieu Desnoyers
wrote:
> The vmalloc space needed by cpu_opv is bound by the number of pages
> a cpu_opv call can touch.
No it's not.
You can have a thousand different processes doing cpu_opv at the same time.
A *single* cpu_opv may me limited toi "only" a meg
- On Apr 12, 2018, at 4:07 PM, Linus Torvalds torva...@linux-foundation.org
wrote:
> On Thu, Apr 12, 2018 at 12:59 PM, Mathieu Desnoyers
> wrote:
>>
>> What are your concerns about page pinning ?
>
> Pretty much everything.
>
> It's the most complex part by far, and the vmalloc space is a
> Can we plan on merging just the plain rseq parts *without* this all
> first, and then see the cpu_opv thing as a "maybe future expansion"
> part.
That would be the right way to go. I doubt anybody really needs cpu_opv.
We already have other code (e.g. vgettimeofday) which cannot
be single stepp
On Thu, Apr 12, 2018 at 12:59 PM, Mathieu Desnoyers
wrote:
>
> What are your concerns about page pinning ?
Pretty much everything.
It's the most complex part by far, and the vmalloc space is a limited
resource on 32-bit architectures.
> Do you have an alternative approach in mind ?
Do everythi
- On Apr 12, 2018, at 3:43 PM, Linus Torvalds torva...@linux-foundation.org
wrote:
> On Thu, Apr 12, 2018 at 12:27 PM, Mathieu Desnoyers
> wrote:
>> The cpu_opv system call executes a vector of operations on behalf of
>> user-space on a specific CPU with preemption disabled. It is inspired
>
On Thu, Apr 12, 2018 at 12:27 PM, Mathieu Desnoyers
wrote:
> The cpu_opv system call executes a vector of operations on behalf of
> user-space on a specific CPU with preemption disabled. It is inspired
> by readv() and writev() system calls which take a "struct iovec"
> array as argument.
Do we r
The cpu_opv system call executes a vector of operations on behalf of
user-space on a specific CPU with preemption disabled. It is inspired
by readv() and writev() system calls which take a "struct iovec"
array as argument.
The operations available are: comparison, memcpy, add, or, and, xor,
left s
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