kernel/sched/psi.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 7d89d7bb921c5ae5a428df282e64ee5692e26fe0
Gitweb: https://git.kernel.org/tip/7d89d7bb921c5ae5a428df282e64ee5692e26fe0
Author: Chengming Zhou <zhouchengming@bytedance.com>
AuthorDate: Mon, 10 Oct 2022 18:42:06 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 27 Oct 2022 11:01:23 +02:00
sched/psi: Fix avgs_work re-arm in psi_avgs_work()
Pavan reported a problem that PSI avgs_work idle shutoff is not
working at all. Because PSI_NONIDLE condition would be observed in
psi_avgs_work()->collect_percpu_times()->get_recent_times() even if
only the kworker running avgs_work on the CPU.
Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off")
avoided the ping-pong wake problem when the worker sleep, psi_avgs_work()
still will always re-arm the avgs_work, so shutoff is not working.
This patch changes to consider current CPU groupc as IDLE if the
kworker running avgs_work is the only task running and no IOWAIT
or MEMSTALL sleep tasks, in which case we will shut off the avgs_work
if other CPUs' groupc are also IDLE.
One potential problem is that the brief period of non-idle time
incurred between the aggregation run and the kworker's dequeue will
be stranded in the per-cpu buckets until avgs_work run next time.
The buckets can hold 4s worth of time, and future activity will wake
the avgs_work with a 2s delay, giving us 2s worth of data we can leave
behind when shut off the avgs_work. If the kworker run other works after
avgs_work shut off and doesn't have any scheduler activities for 2s,
this maybe a problem.
Reported-by: Pavan Kondeti <quic_pkondeti@quicinc.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221010104206.12184-1-zhouchengming@bytedance.com
---
kernel/sched/psi.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index ee2ecc0..f4cdf6f 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -242,6 +242,8 @@ static void get_recent_times(struct psi_group *group, int cpu,
u32 *pchanged_states)
{
struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
+ int current_cpu = raw_smp_processor_id();
+ bool only_avgs_work = false;
u64 now, state_start;
enum psi_states s;
unsigned int seq;
@@ -256,6 +258,15 @@ static void get_recent_times(struct psi_group *group, int cpu,
memcpy(times, groupc->times, sizeof(groupc->times));
state_mask = groupc->state_mask;
state_start = groupc->state_start;
+ /*
+ * This CPU has only avgs_work kworker running, snapshot the
+ * newest times then don't need to re-arm for this groupc.
+ * Normally this kworker will sleep soon and won't wake
+ * avgs_work back up in psi_group_change().
+ */
+ if (current_cpu == cpu && groupc->tasks[NR_RUNNING] == 1 &&
+ !groupc->tasks[NR_IOWAIT] && !groupc->tasks[NR_MEMSTALL])
+ only_avgs_work = true;
} while (read_seqcount_retry(&groupc->seq, seq));
/* Calculate state time deltas against the previous snapshot */
@@ -280,6 +291,10 @@ static void get_recent_times(struct psi_group *group, int cpu,
if (delta)
*pchanged_states |= (1 << s);
}
+
+ /* Clear PSI_NONIDLE so avgs_work won't be re-armed for this groupc */
+ if (only_avgs_work)
+ *pchanged_states &= ~(1 << PSI_NONIDLE);
}
static void calc_avgs(unsigned long avg[3], int missed_periods,Hello,
Thanks for picking this up. There is a newer version which has been acked:
https://lore.kernel.org/all/20221014110551.22695-1-zhouchengming@bytedance.com/
As well another PSI patch that has been acked by Johannes:
https://lore.kernel.org/all/20220926081931.45420-1-zhouchengming@bytedance.com/
Thanks!
On 2022/10/28 14:42, tip-bot2 for Chengming Zhou wrote:
> The following commit has been merged into the sched/core branch of tip:
>
> Commit-ID: 7d89d7bb921c5ae5a428df282e64ee5692e26fe0
> Gitweb: https://git.kernel.org/tip/7d89d7bb921c5ae5a428df282e64ee5692e26fe0
> Author: Chengming Zhou <zhouchengming@bytedance.com>
> AuthorDate: Mon, 10 Oct 2022 18:42:06 +08:00
> Committer: Peter Zijlstra <peterz@infradead.org>
> CommitterDate: Thu, 27 Oct 2022 11:01:23 +02:00
>
> sched/psi: Fix avgs_work re-arm in psi_avgs_work()
>
> Pavan reported a problem that PSI avgs_work idle shutoff is not
> working at all. Because PSI_NONIDLE condition would be observed in
> psi_avgs_work()->collect_percpu_times()->get_recent_times() even if
> only the kworker running avgs_work on the CPU.
>
> Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off")
> avoided the ping-pong wake problem when the worker sleep, psi_avgs_work()
> still will always re-arm the avgs_work, so shutoff is not working.
>
> This patch changes to consider current CPU groupc as IDLE if the
> kworker running avgs_work is the only task running and no IOWAIT
> or MEMSTALL sleep tasks, in which case we will shut off the avgs_work
> if other CPUs' groupc are also IDLE.
>
> One potential problem is that the brief period of non-idle time
> incurred between the aggregation run and the kworker's dequeue will
> be stranded in the per-cpu buckets until avgs_work run next time.
> The buckets can hold 4s worth of time, and future activity will wake
> the avgs_work with a 2s delay, giving us 2s worth of data we can leave
> behind when shut off the avgs_work. If the kworker run other works after
> avgs_work shut off and doesn't have any scheduler activities for 2s,
> this maybe a problem.
>
> Reported-by: Pavan Kondeti <quic_pkondeti@quicinc.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lore.kernel.org/r/20221010104206.12184-1-zhouchengming@bytedance.com
> ---
> kernel/sched/psi.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index ee2ecc0..f4cdf6f 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -242,6 +242,8 @@ static void get_recent_times(struct psi_group *group, int cpu,
> u32 *pchanged_states)
> {
> struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
> + int current_cpu = raw_smp_processor_id();
> + bool only_avgs_work = false;
> u64 now, state_start;
> enum psi_states s;
> unsigned int seq;
> @@ -256,6 +258,15 @@ static void get_recent_times(struct psi_group *group, int cpu,
> memcpy(times, groupc->times, sizeof(groupc->times));
> state_mask = groupc->state_mask;
> state_start = groupc->state_start;
> + /*
> + * This CPU has only avgs_work kworker running, snapshot the
> + * newest times then don't need to re-arm for this groupc.
> + * Normally this kworker will sleep soon and won't wake
> + * avgs_work back up in psi_group_change().
> + */
> + if (current_cpu == cpu && groupc->tasks[NR_RUNNING] == 1 &&
> + !groupc->tasks[NR_IOWAIT] && !groupc->tasks[NR_MEMSTALL])
> + only_avgs_work = true;
> } while (read_seqcount_retry(&groupc->seq, seq));
>
> /* Calculate state time deltas against the previous snapshot */
> @@ -280,6 +291,10 @@ static void get_recent_times(struct psi_group *group, int cpu,
> if (delta)
> *pchanged_states |= (1 << s);
> }
> +
> + /* Clear PSI_NONIDLE so avgs_work won't be re-armed for this groupc */
> + if (only_avgs_work)
> + *pchanged_states &= ~(1 << PSI_NONIDLE);
> }
>
> static void calc_avgs(unsigned long avg[3], int missed_periods,
On Thu, Oct 27, 2022 at 11:50 PM Chengming Zhou
<zhouchengming@bytedance.com> wrote:
>
> Hello,
>
> Thanks for picking this up. There is a newer version which has been acked:
> https://lore.kernel.org/all/20221014110551.22695-1-zhouchengming@bytedance.com/
Hmm. Indeed this seems to be an older version and not the one I asked
Peter to pick up in
https://lore.kernel.org/all/CAJuCfpHeJuZBbv-q+WXjgNHwt_caMomFPL3L9rxosXOrZz3fBw@mail.gmail.com/.
Not sure what went wrong. Peter, could you please replace this one
with https://lore.kernel.org/all/20221014110551.22695-1-zhouchengming@bytedance.com/?
Chengming, please do not top-post next time. Would be better if you
posted your note under the "Link:" field in this email.
Thanks!
>
> As well another PSI patch that has been acked by Johannes:
> https://lore.kernel.org/all/20220926081931.45420-1-zhouchengming@bytedance.com/
>
> Thanks!
>
>
> On 2022/10/28 14:42, tip-bot2 for Chengming Zhou wrote:
> > The following commit has been merged into the sched/core branch of tip:
> >
> > Commit-ID: 7d89d7bb921c5ae5a428df282e64ee5692e26fe0
> > Gitweb: https://git.kernel.org/tip/7d89d7bb921c5ae5a428df282e64ee5692e26fe0
> > Author: Chengming Zhou <zhouchengming@bytedance.com>
> > AuthorDate: Mon, 10 Oct 2022 18:42:06 +08:00
> > Committer: Peter Zijlstra <peterz@infradead.org>
> > CommitterDate: Thu, 27 Oct 2022 11:01:23 +02:00
> >
> > sched/psi: Fix avgs_work re-arm in psi_avgs_work()
> >
> > Pavan reported a problem that PSI avgs_work idle shutoff is not
> > working at all. Because PSI_NONIDLE condition would be observed in
> > psi_avgs_work()->collect_percpu_times()->get_recent_times() even if
> > only the kworker running avgs_work on the CPU.
> >
> > Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off")
> > avoided the ping-pong wake problem when the worker sleep, psi_avgs_work()
> > still will always re-arm the avgs_work, so shutoff is not working.
> >
> > This patch changes to consider current CPU groupc as IDLE if the
> > kworker running avgs_work is the only task running and no IOWAIT
> > or MEMSTALL sleep tasks, in which case we will shut off the avgs_work
> > if other CPUs' groupc are also IDLE.
> >
> > One potential problem is that the brief period of non-idle time
> > incurred between the aggregation run and the kworker's dequeue will
> > be stranded in the per-cpu buckets until avgs_work run next time.
> > The buckets can hold 4s worth of time, and future activity will wake
> > the avgs_work with a 2s delay, giving us 2s worth of data we can leave
> > behind when shut off the avgs_work. If the kworker run other works after
> > avgs_work shut off and doesn't have any scheduler activities for 2s,
> > this maybe a problem.
> >
> > Reported-by: Pavan Kondeti <quic_pkondeti@quicinc.com>
> > Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Link: https://lore.kernel.org/r/20221010104206.12184-1-zhouchengming@bytedance.com
> > ---
> > kernel/sched/psi.c | 15 +++++++++++++++
> > 1 file changed, 15 insertions(+)
> >
> > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> > index ee2ecc0..f4cdf6f 100644
> > --- a/kernel/sched/psi.c
> > +++ b/kernel/sched/psi.c
> > @@ -242,6 +242,8 @@ static void get_recent_times(struct psi_group *group, int cpu,
> > u32 *pchanged_states)
> > {
> > struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
> > + int current_cpu = raw_smp_processor_id();
> > + bool only_avgs_work = false;
> > u64 now, state_start;
> > enum psi_states s;
> > unsigned int seq;
> > @@ -256,6 +258,15 @@ static void get_recent_times(struct psi_group *group, int cpu,
> > memcpy(times, groupc->times, sizeof(groupc->times));
> > state_mask = groupc->state_mask;
> > state_start = groupc->state_start;
> > + /*
> > + * This CPU has only avgs_work kworker running, snapshot the
> > + * newest times then don't need to re-arm for this groupc.
> > + * Normally this kworker will sleep soon and won't wake
> > + * avgs_work back up in psi_group_change().
> > + */
> > + if (current_cpu == cpu && groupc->tasks[NR_RUNNING] == 1 &&
> > + !groupc->tasks[NR_IOWAIT] && !groupc->tasks[NR_MEMSTALL])
> > + only_avgs_work = true;
> > } while (read_seqcount_retry(&groupc->seq, seq));
> >
> > /* Calculate state time deltas against the previous snapshot */
> > @@ -280,6 +291,10 @@ static void get_recent_times(struct psi_group *group, int cpu,
> > if (delta)
> > *pchanged_states |= (1 << s);
> > }
> > +
> > + /* Clear PSI_NONIDLE so avgs_work won't be re-armed for this groupc */
> > + if (only_avgs_work)
> > + *pchanged_states &= ~(1 << PSI_NONIDLE);
> > }
> >
> > static void calc_avgs(unsigned long avg[3], int missed_periods,
On Fri, Oct 28, 2022 at 08:58:03AM -0700, Suren Baghdasaryan wrote: > Not sure what went wrong. Peter, could you please replace this one Probably me being an idiot and searching on subject instead of msgid :/ I'll go fix up -- tomorrow though, it's late and I'm likely to mess it up again.
On Fri, Oct 28, 2022 at 09:53:57PM +0200, Peter Zijlstra wrote: > On Fri, Oct 28, 2022 at 08:58:03AM -0700, Suren Baghdasaryan wrote: > > > Not sure what went wrong. Peter, could you please replace this one > > Probably me being an idiot and searching on subject instead of msgid :/ > > I'll go fix up -- tomorrow though, it's late and I'm likely to mess it > up again. Can you please check queue.git/sched/core ; did I get it right this time?
On 2022/10/29 19:55, Peter Zijlstra wrote: > On Fri, Oct 28, 2022 at 09:53:57PM +0200, Peter Zijlstra wrote: >> On Fri, Oct 28, 2022 at 08:58:03AM -0700, Suren Baghdasaryan wrote: >> >>> Not sure what went wrong. Peter, could you please replace this one >> >> Probably me being an idiot and searching on subject instead of msgid :/ >> >> I'll go fix up -- tomorrow though, it's late and I'm likely to mess it >> up again. > > Can you please check queue.git/sched/core ; did I get it right this > time? I just checked that three patches, LGTM. And would you mind picking up this, by the way? https://lore.kernel.org/all/20220926081931.45420-1-zhouchengming@bytedance.com/ Thanks!
On Sat, Oct 29, 2022 at 5:42 AM Chengming Zhou <zhouchengming@bytedance.com> wrote: > > On 2022/10/29 19:55, Peter Zijlstra wrote: > > On Fri, Oct 28, 2022 at 09:53:57PM +0200, Peter Zijlstra wrote: > >> On Fri, Oct 28, 2022 at 08:58:03AM -0700, Suren Baghdasaryan wrote: > >> > >>> Not sure what went wrong. Peter, could you please replace this one > >> > >> Probably me being an idiot and searching on subject instead of msgid :/ > >> > >> I'll go fix up -- tomorrow though, it's late and I'm likely to mess it > >> up again. > > > > Can you please check queue.git/sched/core ; did I get it right this > > time? > > I just checked that three patches, LGTM. Yep, all three patches are correct. Thanks! > > And would you mind picking up this, by the way? > > https://lore.kernel.org/all/20220926081931.45420-1-zhouchengming@bytedance.com/ > > Thanks!
On 2022/10/28 23:58, Suren Baghdasaryan wrote:
> On Thu, Oct 27, 2022 at 11:50 PM Chengming Zhou
> <zhouchengming@bytedance.com> wrote:
>>
>> Hello,
>>
>> Thanks for picking this up. There is a newer version which has been acked:
>> https://lore.kernel.org/all/20221014110551.22695-1-zhouchengming@bytedance.com/
>
> Hmm. Indeed this seems to be an older version and not the one I asked
> Peter to pick up in
> https://lore.kernel.org/all/CAJuCfpHeJuZBbv-q+WXjgNHwt_caMomFPL3L9rxosXOrZz3fBw@mail.gmail.com/.
> Not sure what went wrong. Peter, could you please replace this one
> with https://lore.kernel.org/all/20221014110551.22695-1-zhouchengming@bytedance.com/?
Oh, I didn't notice that email.
>
> Chengming, please do not top-post next time. Would be better if you
> posted your note under the "Link:" field in this email.
Got it, I will do next time.
Thanks!
> Thanks!
>
>>
>> As well another PSI patch that has been acked by Johannes:
>> https://lore.kernel.org/all/20220926081931.45420-1-zhouchengming@bytedance.com/
>>
>> Thanks!
>>
>>
>> On 2022/10/28 14:42, tip-bot2 for Chengming Zhou wrote:
>>> The following commit has been merged into the sched/core branch of tip:
>>>
>>> Commit-ID: 7d89d7bb921c5ae5a428df282e64ee5692e26fe0
>>> Gitweb: https://git.kernel.org/tip/7d89d7bb921c5ae5a428df282e64ee5692e26fe0
>>> Author: Chengming Zhou <zhouchengming@bytedance.com>
>>> AuthorDate: Mon, 10 Oct 2022 18:42:06 +08:00
>>> Committer: Peter Zijlstra <peterz@infradead.org>
>>> CommitterDate: Thu, 27 Oct 2022 11:01:23 +02:00
>>>
>>> sched/psi: Fix avgs_work re-arm in psi_avgs_work()
>>>
>>> Pavan reported a problem that PSI avgs_work idle shutoff is not
>>> working at all. Because PSI_NONIDLE condition would be observed in
>>> psi_avgs_work()->collect_percpu_times()->get_recent_times() even if
>>> only the kworker running avgs_work on the CPU.
>>>
>>> Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off")
>>> avoided the ping-pong wake problem when the worker sleep, psi_avgs_work()
>>> still will always re-arm the avgs_work, so shutoff is not working.
>>>
>>> This patch changes to consider current CPU groupc as IDLE if the
>>> kworker running avgs_work is the only task running and no IOWAIT
>>> or MEMSTALL sleep tasks, in which case we will shut off the avgs_work
>>> if other CPUs' groupc are also IDLE.
>>>
>>> One potential problem is that the brief period of non-idle time
>>> incurred between the aggregation run and the kworker's dequeue will
>>> be stranded in the per-cpu buckets until avgs_work run next time.
>>> The buckets can hold 4s worth of time, and future activity will wake
>>> the avgs_work with a 2s delay, giving us 2s worth of data we can leave
>>> behind when shut off the avgs_work. If the kworker run other works after
>>> avgs_work shut off and doesn't have any scheduler activities for 2s,
>>> this maybe a problem.
>>>
>>> Reported-by: Pavan Kondeti <quic_pkondeti@quicinc.com>
>>> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>>> Link: https://lore.kernel.org/r/20221010104206.12184-1-zhouchengming@bytedance.com
>>> ---
>>> kernel/sched/psi.c | 15 +++++++++++++++
>>> 1 file changed, 15 insertions(+)
>>>
>>> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
>>> index ee2ecc0..f4cdf6f 100644
>>> --- a/kernel/sched/psi.c
>>> +++ b/kernel/sched/psi.c
>>> @@ -242,6 +242,8 @@ static void get_recent_times(struct psi_group *group, int cpu,
>>> u32 *pchanged_states)
>>> {
>>> struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
>>> + int current_cpu = raw_smp_processor_id();
>>> + bool only_avgs_work = false;
>>> u64 now, state_start;
>>> enum psi_states s;
>>> unsigned int seq;
>>> @@ -256,6 +258,15 @@ static void get_recent_times(struct psi_group *group, int cpu,
>>> memcpy(times, groupc->times, sizeof(groupc->times));
>>> state_mask = groupc->state_mask;
>>> state_start = groupc->state_start;
>>> + /*
>>> + * This CPU has only avgs_work kworker running, snapshot the
>>> + * newest times then don't need to re-arm for this groupc.
>>> + * Normally this kworker will sleep soon and won't wake
>>> + * avgs_work back up in psi_group_change().
>>> + */
>>> + if (current_cpu == cpu && groupc->tasks[NR_RUNNING] == 1 &&
>>> + !groupc->tasks[NR_IOWAIT] && !groupc->tasks[NR_MEMSTALL])
>>> + only_avgs_work = true;
>>> } while (read_seqcount_retry(&groupc->seq, seq));
>>>
>>> /* Calculate state time deltas against the previous snapshot */
>>> @@ -280,6 +291,10 @@ static void get_recent_times(struct psi_group *group, int cpu,
>>> if (delta)
>>> *pchanged_states |= (1 << s);
>>> }
>>> +
>>> + /* Clear PSI_NONIDLE so avgs_work won't be re-armed for this groupc */
>>> + if (only_avgs_work)
>>> + *pchanged_states &= ~(1 << PSI_NONIDLE);
>>> }
>>>
>>> static void calc_avgs(unsigned long avg[3], int missed_periods,
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