lkml.org 
[lkml]   [2023]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [External] Re: [PATCH v2 2/2] sched/core: Avoid double calling update_rq_clock()
From


On 2023/5/10 Peter Zijlstra wrote:
> On Wed, May 10, 2023 at 04:34:50PM +0800, Hao Jia wrote:

>> For the __balance_push_cpu_stop() case, we remove update_rq_clock() from
>> the __migrate_task() function to avoid double updating the rq clock.
>> And in order to avoid missing rq clock update, add update_rq_clock()
>> call before migration_cpu_stop() calls __migrate_task().
>>
>> For the unthrottle_cfs_rq() case, we use rq_clock_start_loop_update() to
>> prevent multiple calls to update_rq_clock() in unthrottle_cfs_rq().
>>
>> Note that the rq clock has been updated before the set_rq_offline()
>> function runs, so we don't need to call update_rq_clock() in
>> unthrottle_offline_cfs_rqs().
>
> This reads like 3 separate issues -- in which case this ought to be 3
> separate patches.

I will do it in the next version.

Thanks,
Hao

>
>
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index ec7b3e0a2b20..9c712f29e5a4 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -1536,6 +1536,27 @@ static inline void rq_clock_skip_update(struct rq *rq)
>> rq->clock_update_flags |= RQCF_REQ_SKIP;
>> }
>>
>> +/*
>> + * During cpu offlining and rq wide unthrottling, we can trigger
>> + * an update_rq_clock() for several cfs and rt runqueues (Typically
>> + * when using list_for_each_entry_*)
>> + * rq_clock_start_loop_update() can be called after updating the clock
>> + * once and before iterating over the list to prevent multiple update.
>> + * After the iterative traversal, we need to call rq_clock_stop_loop_update()
>> + * to restore rq->clock_update_flags.
> ^^^^^^^
>> + */
>> +static inline void rq_clock_start_loop_update(struct rq *rq)
>> +{
>> + lockdep_assert_rq_held(rq);
>> + rq->clock_update_flags |= RQCF_ACT_SKIP;
>> +}
>> +
>> +static inline void rq_clock_stop_loop_update(struct rq *rq)
>> +{
>> + lockdep_assert_rq_held(rq);
>> + rq->clock_update_flags &= ~RQCF_ACT_SKIP;
>> +}
>
> This does not restore the flag, it clears the flag.

Thanks for your review.
I will also modify it in the next version.

Thanks,
Hao

\
 
 \ /
  Last update: 2023-05-11 06:06    [W:0.040 / U:1.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site