Commit 1066d1b6 authored by Yafang Shao's avatar Yafang Shao Committed by Peter Zijlstra
Browse files

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This patch also removes an out-of-date comment pointed by Matthew.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: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/1584408485-1921-1-git-send-email-laoar.shao@gmail.com
parent a0fe6ba6

include/linux/sched.h

+4 −2
Original line number Diff line number Diff line
@@ -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 */

kernel/sched/psi.c

+6 −6
Original line number Diff line number Diff line
@@ -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)

kernel/sched/stats.h

+5 −5
Original line number Diff line number Diff line
@@ -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 */

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