2021-02-07 07:26:08

by Chengming Zhou

Subject: [PATCH] psi: Add PSI_CPU_FULL state

The FULL state doesn't exist for the CPU resource at the system level,
but exist at the cgroup level, means all non-idle tasks in a cgroup are
delayed on the CPU resource which used by others outside of the cgroup.

Co-developed-by: Muchun Song <[email protected]>
Signed-off-by: Muchun Song <[email protected]>
Signed-off-by: Chengming Zhou <[email protected]>
---
include/linux/psi_types.h | 3 ++-
kernel/sched/psi.c | 14 +++++++++++---
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index b95f3211566a..0a23300d49af 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -50,9 +50,10 @@ enum psi_states {
PSI_MEM_SOME,
PSI_MEM_FULL,
PSI_CPU_SOME,
+ PSI_CPU_FULL,
/* Only per-CPU, to weigh the CPU in the global average: */
PSI_NONIDLE,
- NR_PSI_STATES = 6,
+ NR_PSI_STATES = 7,
};

enum psi_aggregators {
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 39d758a15a57..c572ad529d87 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -34,7 +34,10 @@
* delayed on that resource such that nobody is advancing and the CPU
* goes idle. This leaves both workload and CPU unproductive.
*
- * (Naturally, the FULL state doesn't exist for the CPU resource.)
+ * Naturally, the FULL state doesn't exist for the CPU resource at the
+ * system level, but exist at the cgroup level, means all non-idle tasks
+ * in a cgroup are delayed on the CPU resource which used by others outside
+ * of the cgroup.
*
* SOME = nr_delayed_tasks != 0
* FULL = nr_delayed_tasks != 0 && nr_running_tasks == 0
@@ -225,6 +228,8 @@ static bool test_state(unsigned int *tasks, enum psi_states state)
return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING];
case PSI_CPU_SOME:
return tasks[NR_RUNNING] > tasks[NR_ONCPU];
+ case PSI_CPU_FULL:
+ return tasks[NR_RUNNING] && !tasks[NR_ONCPU];
case PSI_NONIDLE:
return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||
tasks[NR_RUNNING];
@@ -678,8 +683,11 @@ static void record_times(struct psi_group_cpu *groupc, int cpu,
}
}

- if (groupc->state_mask & (1 << PSI_CPU_SOME))
+ if (groupc->state_mask & (1 << PSI_CPU_SOME)) {
groupc->times[PSI_CPU_SOME] += delta;
+ if (groupc->state_mask & (1 << PSI_CPU_FULL))
+ groupc->times[PSI_CPU_FULL] += delta;
+ }

if (groupc->state_mask & (1 << PSI_NONIDLE))
groupc->times[PSI_NONIDLE] += delta;
@@ -1018,7 +1026,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
group->avg_next_update = update_averages(group, now);
mutex_unlock(&group->avgs_lock);

- for (full = 0; full < 2 - (res == PSI_CPU); full++) {
+ for (full = 0; full < 2; full++) {
unsigned long avg[3];
u64 total;
int w;
--
2.11.0

2021-02-08 20:02:26

by Johannes Weiner

Subject: Re: [PATCH] psi: Add PSI_CPU_FULL state

On Sun, Feb 07, 2021 at 03:24:02PM +0800, Chengming Zhou wrote:
> The FULL state doesn't exist for the CPU resource at the system level,
> but exist at the cgroup level, means all non-idle tasks in a cgroup are
> delayed on the CPU resource which used by others outside of the cgroup.
>
> Co-developed-by: Muchun Song <[email protected]>
> Signed-off-by: Muchun Song <[email protected]>
> Signed-off-by: Chengming Zhou <[email protected]>

Acked-by: Johannes Weiner <[email protected]>

That metric's come up in our production environment recently as well,
it makes a lot of sense.

In addition to outside competition, this also applies to downtimes
enforced by cpu.max - another cgroup usecase that is worth mentioning
in the changelog & code comment.

Thanks

2021-02-09 01:53:33

by Chengming Zhou

Subject: Re: [External] Re: [PATCH] psi: Add PSI_CPU_FULL state

在 2021/2/9 上午2:18, Johannes Weiner 写道:

> On Sun, Feb 07, 2021 at 03:24:02PM +0800, Chengming Zhou wrote:
>> The FULL state doesn't exist for the CPU resource at the system level,
>> but exist at the cgroup level, means all non-idle tasks in a cgroup are
>> delayed on the CPU resource which used by others outside of the cgroup.
>>
>> Co-developed-by: Muchun Song <[email protected]>
>> Signed-off-by: Muchun Song <[email protected]>
>> Signed-off-by: Chengming Zhou <[email protected]>
> Acked-by: Johannes Weiner <[email protected]>
>
> That metric's come up in our production environment recently as well,
> it makes a lot of sense.
>
> In addition to outside competition, this also applies to downtimes
> enforced by cpu.max - another cgroup usecase that is worth mentioning
> in the changelog & code comment.

Thank you, I will add this and send patch-v2.

> Thanks