Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Ingo Molnar wrote: > > CPU hotplug and changing the affinity mask are the more complex cases, > > because > > there migrating or not migrating is a correctness issue: > > > > - CPU hotplug has to be aware of this anyway,

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Ingo Molnar wrote: > > CPU hotplug and changing the affinity mask are the more complex cases, > > because > > there migrating or not migrating is a correctness issue: > > > > - CPU hotplug has to be aware of this anyway, regardless of whether

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 01:56:12PM +0200, Thomas Gleixner wrote: > A pointer to the effective mask is definitely enough. And that's what we > need for migrate_disable() as well. That still leaves the storage > requirement to MIPS. So then you're back to Ingo's proposal, right?

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 01:56:12PM +0200, Thomas Gleixner wrote: > A pointer to the effective mask is definitely enough. And that's what we > need for migrate_disable() as well. That still leaves the storage > requirement to MIPS. So then you're back to Ingo's proposal, right?

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 01:03:16PM +0200, Thomas Gleixner wrote: > > > Fair enough, but I prefer to have the ability for a temporary restriction > > of the user space visible cpus allowed mask in the core code, which can be > > used for both

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 01:03:16PM +0200, Thomas Gleixner wrote: > > > Fair enough, but I prefer to have the ability for a temporary restriction > > of the user space visible cpus allowed mask in the core code, which can be > > used for both

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 01:03:16PM +0200, Thomas Gleixner wrote: > Fair enough, but I prefer to have the ability for a temporary restriction > of the user space visible cpus allowed mask in the core code, which can be > used for both migrate_disable() and things like that MIPS FPU stuff rather >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 01:03:16PM +0200, Thomas Gleixner wrote: > Fair enough, but I prefer to have the ability for a temporary restriction > of the user space visible cpus allowed mask in the core code, which can be > used for both migrate_disable() and things like that MIPS FPU stuff rather >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 12:58:27PM +0200, Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Peter Zijlstra wrote: > > Because mainline will not get anything other than prempt_disable() for > > migrate_disable(). > > I'm not yet convinced of that. There is enough stuff which pointlessly > disables

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 12:58:27PM +0200, Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Peter Zijlstra wrote: > > Because mainline will not get anything other than prempt_disable() for > > migrate_disable(). > > I'm not yet convinced of that. There is enough stuff which pointlessly > disables

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Ingo Molnar wrote: > CPU hotplug and changing the affinity mask are the more complex cases, > because > there migrating or not migrating is a correctness issue: > > - CPU hotplug has to be aware of this anyway, regardless of whether it's > solved >via a counter of the

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Ingo Molnar wrote: > CPU hotplug and changing the affinity mask are the more complex cases, > because > there migrating or not migrating is a correctness issue: > > - CPU hotplug has to be aware of this anyway, regardless of whether it's > solved >via a counter of the

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 12:47:21PM +0200, Thomas Gleixner wrote: > > On Thu, 6 Apr 2017, Peter Zijlstra wrote: > > > > IIRC MIPS has a case where only 1 in N cores has an FPU. And once a task > > > uses FPU, it gets affined to the core that has one or

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 12:47:21PM +0200, Thomas Gleixner wrote: > > On Thu, 6 Apr 2017, Peter Zijlstra wrote: > > > > IIRC MIPS has a case where only 1 in N cores has an FPU. And once a task > > > uses FPU, it gets affined to the core that has one or

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Ingo Molnar wrote: > > > Sorry if this is a back and forth - I was somehow convinced that we do need > > to > > frob the cpus_allowed mask to get this functionality - but in hindsight I > > think the counter should be enough.

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Ingo Molnar wrote: > > > Sorry if this is a back and forth - I was somehow convinced that we do need > > to > > frob the cpus_allowed mask to get this functionality - but in hindsight I > > think the counter should be enough. > > > > I.e. just

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 11:25:42AM +0200, Sebastian Andrzej Siewior wrote: > > > I.e. just have a counter and these two APIs: > > > > > > static inline void migrate_disable(void) > > > { > > >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 11:25:42AM +0200, Sebastian Andrzej Siewior wrote: > > > I.e. just have a counter and these two APIs: > > > > > > static inline void migrate_disable(void) > > > { > > >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 12:47:21PM +0200, Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Peter Zijlstra wrote: > > IIRC MIPS has a case where only 1 in N cores has an FPU. And once a task > > uses FPU, it gets affined to the core that has one or something like > > that. > > > > Of course, nothing

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 12:47:21PM +0200, Thomas Gleixner wrote: > On Thu, 6 Apr 2017, Peter Zijlstra wrote: > > IIRC MIPS has a case where only 1 in N cores has an FPU. And once a task > > uses FPU, it gets affined to the core that has one or something like > > that. > > > > Of course, nothing

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 11:46:33AM +0200, Sebastian Andrzej Siewior wrote: > > On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote: > > > On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > > > > While converting the existing

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 11:46:33AM +0200, Sebastian Andrzej Siewior wrote: > > On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote: > > > On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > > > > While converting the existing

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Ingo Molnar wrote: > Sorry if this is a back and forth - I was somehow convinced that we do need > to > frob the cpus_allowed mask to get this functionality - but in hindsight I > think > the counter should be enough. > > I.e. just have a counter and these two APIs: > >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, 6 Apr 2017, Ingo Molnar wrote: > Sorry if this is a back and forth - I was somehow convinced that we do need > to > frob the cpus_allowed mask to get this functionality - but in hindsight I > think > the counter should be enough. > > I.e. just have a counter and these two APIs: > >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 11:46:33AM +0200, Sebastian Andrzej Siewior wrote: > On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote: > > On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > > > While converting the existing users I tried to stick with the rules > > > above

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 11:46:33AM +0200, Sebastian Andrzej Siewior wrote: > On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote: > > On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > > > While converting the existing users I tried to stick with the rules > > > above

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote: > On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > > While converting the existing users I tried to stick with the rules > > above however… well mostly CPUFREQ tries to temporary switch the CPU > > mask to do

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-06 11:32:24 [+0200], Peter Zijlstra wrote: > On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > > While converting the existing users I tried to stick with the rules > > above however… well mostly CPUFREQ tries to temporary switch the CPU > > mask to do

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 11:25:42AM +0200, Sebastian Andrzej Siewior wrote: > > I.e. just have a counter and these two APIs: > > > > static inline void migrate_disable(void) > > { > > current->migration_disabled++; > plus > if (current->migration_disabled ==

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 11:25:42AM +0200, Sebastian Andrzej Siewior wrote: > > I.e. just have a counter and these two APIs: > > > > static inline void migrate_disable(void) > > { > > current->migration_disabled++; > plus > if (current->migration_disabled ==

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 11:35:45AM +0200, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 10:01:39AM +0200, Ingo Molnar wrote: > > I.e. just have a counter and these two APIs: > > > > static inline void migrate_disable(void) > > { > > current->migration_disabled++;

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 11:35:45AM +0200, Peter Zijlstra wrote: > On Thu, Apr 06, 2017 at 10:01:39AM +0200, Ingo Molnar wrote: > > I.e. just have a counter and these two APIs: > > > > static inline void migrate_disable(void) > > { > > current->migration_disabled++;

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 10:01:39AM +0200, Ingo Molnar wrote: > I.e. just have a counter and these two APIs: > > static inline void migrate_disable(void) > { > current->migration_disabled++; > } > > ... > > static inline void

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Thu, Apr 06, 2017 at 10:01:39AM +0200, Ingo Molnar wrote: > I.e. just have a counter and these two APIs: > > static inline void migrate_disable(void) > { > current->migration_disabled++; > } > > ... > > static inline void

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Wed, Apr 05, 2017 at 09:39:43AM +0200, Ingo Molnar wrote: > > While converting the existing users I tried to stick with the rules > > above however… well mostly CPUFREQ tries to temporary switch the CPU > > mask to do something on a certain CPU and then switches the mask back it > > its

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Wed, Apr 05, 2017 at 09:39:43AM +0200, Ingo Molnar wrote: > > While converting the existing users I tried to stick with the rules > > above however… well mostly CPUFREQ tries to temporary switch the CPU > > mask to do something on a certain CPU and then switches the mask back it > > its

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > While converting the existing users I tried to stick with the rules > above however… well mostly CPUFREQ tries to temporary switch the CPU > mask to do something on a certain CPU and then switches the mask back it > its

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On Tue, Apr 04, 2017 at 08:42:02PM +0200, Sebastian Andrzej Siewior wrote: > While converting the existing users I tried to stick with the rules > above however… well mostly CPUFREQ tries to temporary switch the CPU > mask to do something on a certain CPU and then switches the mask back it > its

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-06 10:01:39 [+0200], Ingo Molnar wrote: > > * Sebastian Andrzej Siewior wrote: > > > On 2017-04-06 08:16:22 [+0200], Ingo Molnar wrote: > > > > > > * Sebastian Andrzej Siewior wrote: > > > > > > > On 2017-04-05 09:39:43 [+0200], Ingo

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-06 10:01:39 [+0200], Ingo Molnar wrote: > > * Sebastian Andrzej Siewior wrote: > > > On 2017-04-06 08:16:22 [+0200], Ingo Molnar wrote: > > > > > > * Sebastian Andrzej Siewior wrote: > > > > > > > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > > > > > > > So maybe we

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Sebastian Andrzej Siewior wrote: > On 2017-04-06 08:16:22 [+0200], Ingo Molnar wrote: > > > > * Sebastian Andrzej Siewior wrote: > > > > > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > > > > > So maybe we could add the following

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Sebastian Andrzej Siewior wrote: > On 2017-04-06 08:16:22 [+0200], Ingo Molnar wrote: > > > > * Sebastian Andrzej Siewior wrote: > > > > > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > > > > > So maybe we could add the following facility: > > > > > > > > ptr =

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-06 08:16:22 [+0200], Ingo Molnar wrote: > > * Sebastian Andrzej Siewior wrote: > > > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > > > So maybe we could add the following facility: > > > > > > ptr = sched_migrate_to_cpu_save(cpu); > > > > > >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-06 08:16:22 [+0200], Ingo Molnar wrote: > > * Sebastian Andrzej Siewior wrote: > > > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > > > So maybe we could add the following facility: > > > > > > ptr = sched_migrate_to_cpu_save(cpu); > > > > > > ... > > > > > >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Sebastian Andrzej Siewior wrote: > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > So maybe we could add the following facility: > > > > ptr = sched_migrate_to_cpu_save(cpu); > > > > ... > > > > sched_migrate_to_cpu_restore(ptr); BTW., and

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Sebastian Andrzej Siewior wrote: > On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > > > So maybe we could add the following facility: > > > > ptr = sched_migrate_to_cpu_save(cpu); > > > > ... > > > > sched_migrate_to_cpu_restore(ptr); BTW., and I'm sure this has come up

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > So maybe we could add the following facility: > > ptr = sched_migrate_to_cpu_save(cpu); > > ... > > sched_migrate_to_cpu_restore(ptr); > > ... and use it in the cpufreq code. Then -rt could simply define >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

On 2017-04-05 09:39:43 [+0200], Ingo Molnar wrote: > > So maybe we could add the following facility: > > ptr = sched_migrate_to_cpu_save(cpu); > > ... > > sched_migrate_to_cpu_restore(ptr); > > ... and use it in the cpufreq code. Then -rt could simply define >

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Sebastian Andrzej Siewior wrote: > In commit 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed() > wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not > much difference in !RT but in RT we used this to implement > migrate_disable(). Within a

Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

* Sebastian Andrzej Siewior wrote: > In commit 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed() > wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not > much difference in !RT but in RT we used this to implement > migrate_disable(). Within a migrate_disable()

[RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

In commit 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed() wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not much difference in !RT but in RT we used this to implement migrate_disable(). Within a migrate_disable() section the CPU mask is restricted to single CPU

[RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask

In commit 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed() wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not much difference in !RT but in RT we used this to implement migrate_disable(). Within a migrate_disable() section the CPU mask is restricted to single CPU