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psi: Move PF_MEMSTALL out of task->flags

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The task->flags is a 32-bits flag, in which 31 bits have already been
consumed. So it is hardly to introduce other new per process flag.
Currently there're still enough spaces in the bit-field section of
task_struct, so we can define the memstall state as a single bit in
task_struct instead.
This patch also removes an out-of-date comment pointed by Matthew.

Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/1584408485-1921-1-git-send-email-laoar.shao@gmail.com
This commit is contained in:
Yafang Shao
2020-03-16 21:28:05 -04:00
committed by Peter Zijlstra
parent a0fe6ba690
commit 1066d1b697
3 changed files with 15 additions and 13 deletions
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12
kernel/sched/psi.c
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@@ -865,17 +865,17 @@ void psi_memstall_enter(unsigned long *flags)
if (static_branch_likely(&psi_disabled))
return;
*flags = current->flags & PF_MEMSTALL;
*flags = current->in_memstall;
if (*flags)
return;
/*
* PF_MEMSTALL setting & accounting needs to be atomic wrt
* in_memstall setting & accounting needs to be atomic wrt
* changes to the task's scheduling state, otherwise we can
* race with CPU migration.
*/
rq = this_rq_lock_irq(&rf);
current->flags |= PF_MEMSTALL;
current->in_memstall = 1;
psi_task_change(current, 0, TSK_MEMSTALL);
rq_unlock_irq(rq, &rf);
@@ -898,13 +898,13 @@ void psi_memstall_leave(unsigned long *flags)
if (*flags)
return;
/*
* PF_MEMSTALL clearing & accounting needs to be atomic wrt
* in_memstall clearing & accounting needs to be atomic wrt
* changes to the task's scheduling state, otherwise we could
* race with CPU migration.
*/
rq = this_rq_lock_irq(&rf);
current->flags &= ~PF_MEMSTALL;
current->in_memstall = 0;
psi_task_change(current, TSK_MEMSTALL, 0);
rq_unlock_irq(rq, &rf);
@@ -970,7 +970,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)
} else if (task->in_iowait)
task_flags = TSK_IOWAIT;
if (task->flags & PF_MEMSTALL)
if (task->in_memstall)
task_flags |= TSK_MEMSTALL;
if (task_flags)