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Commit be807b64 authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Patrick Daly
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psi: introduce state_mask to represent stalled psi states 

The psi monitoring patches will need to determine the same states as
record_times().  To avoid calculating them twice, maintain a state mask
that can be consulted cheaply.  Do this in a separate patch to keep the
churn in the main feature patch at a minimum.

This adds 4-byte state_mask member into psi_group_cpu struct which results
in its first cacheline-aligned part becoming 52 bytes long.  Add explicit
values to enumeration element counters that affect psi_group_cpu struct
size.

Link: http://lkml.kernel.org/r/20190124211518.244221-4-surenb@google.com


Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Change-Id: Ic088406df80432d2e8f315a6d8b6181b28fd435f
Patch-mainline: linux-mm @ 03/19/2019, 23:56
Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent 680e58e7

include/linux/psi_types.h

+6 −3
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ enum psi_task_count { 
	NR_IOWAIT,

	NR_MEMSTALL,

	NR_RUNNING,

	NR_PSI_TASK_COUNTS,

	NR_PSI_TASK_COUNTS = 3,

};



/* Task state bitmasks */
@@ -24,7 +24,7 @@ enum psi_res { 
	PSI_IO,

	PSI_MEM,

	PSI_CPU,

	NR_PSI_RESOURCES,

	NR_PSI_RESOURCES = 3,

};



/*
@@ -41,7 +41,7 @@ enum psi_states { 
	PSI_CPU_SOME,

	/* Only per-CPU, to weigh the CPU in the global average: */

	PSI_NONIDLE,

	NR_PSI_STATES,

	NR_PSI_STATES = 6,

};



struct psi_group_cpu {
@@ -53,6 +53,9 @@ struct psi_group_cpu { 
	/* States of the tasks belonging to this group */

	unsigned int tasks[NR_PSI_TASK_COUNTS];



	/* Aggregate pressure state derived from the tasks */

	u32 state_mask;



	/* Period time sampling buckets for each state of interest (ns) */

	u32 times[NR_PSI_STATES];

kernel/sched/psi.c

+19 −10
Original line number Diff line number Diff line
@@ -213,17 +213,17 @@ static bool test_state(unsigned int *tasks, enum psi_states state) 
static void get_recent_times(struct psi_group *group, int cpu, u32 *times)

{

	struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);

	unsigned int tasks[NR_PSI_TASK_COUNTS];

	u64 now, state_start;

	enum psi_states s;

	unsigned int seq;

	int s;

	u32 state_mask;



	/* Snapshot a coherent view of the CPU state */

	do {

		seq = read_seqcount_begin(&groupc->seq);

		now = cpu_clock(cpu);

		memcpy(times, groupc->times, sizeof(groupc->times));

		memcpy(tasks, groupc->tasks, sizeof(groupc->tasks));

		state_mask = groupc->state_mask;

		state_start = groupc->state_start;

	} while (read_seqcount_retry(&groupc->seq, seq));
@@ -239,7 +239,7 @@ static void get_recent_times(struct psi_group *group, int cpu, u32 *times) 
		 * (u32) and our reported pressure close to what's

		 * actually happening.

		 */

		if (test_state(tasks, s))

		if (state_mask & (1 << s))

			times[s] += now - state_start;



		delta = times[s] - groupc->times_prev[s];
@@ -407,15 +407,15 @@ static void record_times(struct psi_group_cpu *groupc, int cpu, 
	delta = now - groupc->state_start;

	groupc->state_start = now;



	if (test_state(groupc->tasks, PSI_IO_SOME)) {

	if (groupc->state_mask & (1 << PSI_IO_SOME)) {

		groupc->times[PSI_IO_SOME] += delta;

		if (test_state(groupc->tasks, PSI_IO_FULL))

		if (groupc->state_mask & (1 << PSI_IO_FULL))

			groupc->times[PSI_IO_FULL] += delta;

	}



	if (test_state(groupc->tasks, PSI_MEM_SOME)) {

	if (groupc->state_mask & (1 << PSI_MEM_SOME)) {

		groupc->times[PSI_MEM_SOME] += delta;

		if (test_state(groupc->tasks, PSI_MEM_FULL))

		if (groupc->state_mask & (1 << PSI_MEM_FULL))

			groupc->times[PSI_MEM_FULL] += delta;

		else if (memstall_tick) {

			u32 sample;
@@ -436,10 +436,10 @@ static void record_times(struct psi_group_cpu *groupc, int cpu, 
		}

	}



	if (test_state(groupc->tasks, PSI_CPU_SOME))

	if (groupc->state_mask & (1 << PSI_CPU_SOME))

		groupc->times[PSI_CPU_SOME] += delta;



	if (test_state(groupc->tasks, PSI_NONIDLE))

	if (groupc->state_mask & (1 << PSI_NONIDLE))

		groupc->times[PSI_NONIDLE] += delta;

}
@@ -448,6 +448,8 @@ static void psi_group_change(struct psi_group *group, int cpu, 
{

	struct psi_group_cpu *groupc;

	unsigned int t, m;

	enum psi_states s;

	u32 state_mask = 0;



	groupc = per_cpu_ptr(group->pcpu, cpu);
@@ -480,6 +482,13 @@ static void psi_group_change(struct psi_group *group, int cpu, 
		if (set & (1 << t))

			groupc->tasks[t]++;



	/* Calculate state mask representing active states */

	for (s = 0; s < NR_PSI_STATES; s++) {

		if (test_state(groupc->tasks, s))

			state_mask |= (1 << s);

	}

	groupc->state_mask = state_mask;



	write_seqcount_end(&groupc->seq);

}