Messages in this thread | | | Date | Thu, 6 Apr 2017 08:16:22 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC PATCH] kernel: sched: Provide a pointer to the valid CPU mask |
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* Sebastian Andrzej Siewior <bigeasy@linutronix.de> 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 before, but why doesn't migrate_disable() use a simple per task flag that the scheduler migration code takes into account?
It should be functionally equivalent to the current solution, and it appears to have a heck of a smaller cross section with the rest of the scheduler.
I.e.:
static inline void migrate_disable(void) { current->migration_disabled++; }
...
static inline void migrate_enable(void) { current->migration_disabled--; }
or so? Then add this flag as a condition to can_migrate_task() et al.
While we generally dislike such flags as they wreck havoc with the scheduler if overused, the cpus_allowed based solution has the exact same effect so it's not like it's a step backwards - and it should also be much faster and less intrusive.
Am I missing some complication?
Thanks,
Ingo
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