From: Chengming Zhou <zhouchengming@bytedance.com>
To: Suren Baghdasaryan <surenb@google.com>
Cc: linux-tip-commits@vger.kernel.org,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Pavan Kondeti <quic_pkondeti@quicinc.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [tip: sched/core] sched/psi: Fix avgs_work re-arm in psi_avgs_work()
Date: Sat, 29 Oct 2022 00:05:45 +0800 [thread overview]
Message-ID: <148c15f7-5f33-b9c1-dca5-73087f078ba5@bytedance.com> (raw)
In-Reply-To: <CAJuCfpHOt1Vfc=ZtAYt_2QamOujfuFtNHAdJe7iBMmDgTLGtyw@mail.gmail.com>
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,
next prev parent reply other threads:[~2022-10-28 16:08 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 14:08 PSI idle-shutoff Pavan Kondeti
2022-09-15 6:20 ` Pavan Kondeti
2022-09-17 5:45 ` Suren Baghdasaryan
2022-10-03 6:11 ` Suren Baghdasaryan
2022-10-05 16:32 ` Suren Baghdasaryan
2022-10-09 12:41 ` Chengming Zhou
2022-10-09 13:17 ` Chengming Zhou
2022-10-10 6:18 ` Pavan Kondeti
2022-10-10 6:43 ` Pavan Kondeti
2022-10-10 6:57 ` [External] " Chengming Zhou
2022-10-10 8:30 ` Chengming Zhou
2022-10-10 9:09 ` Pavan Kondeti
2022-10-10 9:22 ` Chengming Zhou
2022-10-10 20:59 ` Suren Baghdasaryan
2022-10-10 20:33 ` Suren Baghdasaryan
2022-10-10 5:57 ` Pavan Kondeti
2022-10-10 9:01 ` Pavan Kondeti
2022-10-10 6:25 ` Pavan Kondeti
2022-10-10 10:42 ` [PATCH] sched/psi: Fix avgs_work re-arm in psi_avgs_work() Chengming Zhou
2022-10-10 21:21 ` Suren Baghdasaryan
2022-10-11 0:07 ` Chengming Zhou
2022-10-11 17:00 ` Suren Baghdasaryan
2022-10-12 2:10 ` Chengming Zhou
2022-10-12 18:24 ` Suren Baghdasaryan
2022-10-13 2:23 ` Chengming Zhou
2022-10-13 11:06 ` Chengming Zhou
2022-10-13 15:52 ` Johannes Weiner
2022-10-13 16:10 ` Suren Baghdasaryan
2022-10-14 2:03 ` Chengming Zhou
2022-10-14 2:02 ` Chengming Zhou
2022-10-28 6:42 ` [tip: sched/core] " tip-bot2 for Chengming Zhou
2022-10-28 6:50 ` [External] " Chengming Zhou
2022-10-28 15:58 ` Suren Baghdasaryan
2022-10-28 16:05 ` Chengming Zhou [this message]
2022-10-28 19:53 ` Peter Zijlstra
2022-10-29 11:55 ` Peter Zijlstra
2022-10-29 12:40 ` Chengming Zhou
2022-10-29 18:46 ` Suren Baghdasaryan
[not found] ` <20221010105710.171-1-hdanton@sina.com>
2022-10-10 21:16 ` PSI idle-shutoff Suren Baghdasaryan
[not found] ` <20221011113818.340-1-hdanton@sina.com>
2022-10-11 17:11 ` Suren Baghdasaryan
[not found] ` <20221012062034.486-1-hdanton@sina.com>
2022-10-12 15:40 ` Suren Baghdasaryan
2022-10-14 11:05 [PATCH v2] sched/psi: Fix avgs_work re-arm in psi_avgs_work() Chengming Zhou
2022-10-31 10:53 ` [tip: sched/core] " tip-bot2 for Chengming Zhou
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=148c15f7-5f33-b9c1-dca5-73087f078ba5@bytedance.com \
--to=zhouchengming@bytedance.com \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=quic_pkondeti@quicinc.com \
--cc=surenb@google.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).