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psi: Move PF_MEMSTALL out of task->flags 

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This patch also removes an out-of-date comment pointed by Matthew.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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6
include/linux/sched.h
View File

@ -785,9 +785,12 @@ struct task_struct {
unsigned frozen:1;
#endif
#ifdef CONFIG_BLK_CGROUP
/* to be used once the psi infrastructure lands upstream. */
unsigned use_memdelay:1;
#endif
#ifdef CONFIG_PSI
/* Stalled due to lack of memory */
unsigned in_memstall:1;
#endif
unsigned long atomic_flags; /* Flags requiring atomic access. */
@ -1480,7 +1483,6 @@ extern struct pid *cad_pid;
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_MEMSTALL 0x01000000 /* Stalled due to lack of memory */
#define PF_UMH 0x02000000 /* I'm an Usermodehelper process */
#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */
#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */

12
kernel/sched/psi.c
View File

@ -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)

10
kernel/sched/stats.h
View File

@ -70,7 +70,7 @@ static inline void psi_enqueue(struct task_struct *p, bool wakeup)
return;
if (!wakeup || p->sched_psi_wake_requeue) {
if (p->flags & PF_MEMSTALL)
if (p->in_memstall)
set |= TSK_MEMSTALL;
if (p->sched_psi_wake_requeue)
p->sched_psi_wake_requeue = 0;
@ -90,7 +90,7 @@ static inline void psi_dequeue(struct task_struct *p, bool sleep)
return;
if (!sleep) {
if (p->flags & PF_MEMSTALL)
if (p->in_memstall)
clear |= TSK_MEMSTALL;
} else {
/*
@ -117,14 +117,14 @@ static inline void psi_ttwu_dequeue(struct task_struct *p)
* deregister its sleep-persistent psi states from the old
* queue, and let psi_enqueue() know it has to requeue.
*/
if (unlikely(p->in_iowait || (p->flags & PF_MEMSTALL))) {
if (unlikely(p->in_iowait || p->in_memstall)) {
struct rq_flags rf;
struct rq *rq;
int clear = 0;
if (p->in_iowait)
clear |= TSK_IOWAIT;
if (p->flags & PF_MEMSTALL)
if (p->in_memstall)
clear |= TSK_MEMSTALL;
rq = __task_rq_lock(p, &rf);
@ -149,7 +149,7 @@ static inline void psi_task_tick(struct rq *rq)
if (static_branch_likely(&psi_disabled))
return;
if (unlikely(rq->curr->flags & PF_MEMSTALL))
if (unlikely(rq->curr->in_memstall))
psi_memstall_tick(rq->curr, cpu_of(rq));
}
#else /* CONFIG_PSI */