linux-kernel - Re: [PATCH v8 00/25] timer: Move from a push remote at enqueue to a pull at expiry model

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Date:   Thu, 19 Oct 2023 15:47:26 +0200
From:   Anna-Maria Behnsen <anna-maria@...utronix.de>
To:     "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "jstultz@...gle.com" <jstultz@...gle.com>,
        "riel@...riel.com" <riel@...riel.com>,
        "lukasz.luba@....com" <lukasz.luba@....com>,
        "kprateek.nayak@....com" <kprateek.nayak@....com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "frederic@...nel.org" <frederic@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        "arjan@...radead.org" <arjan@...radead.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "ggherdovich@...e.cz" <ggherdovich@...e.cz>,
        "gautham.shenoy@....com" <gautham.shenoy@....com>
Subject: Re: [PATCH v8 00/25] timer: Move from a push remote at enqueue to a
 pull at expiry model

"Pandruvada, Srinivas" <srinivas.pandruvada@...el.com> writes:

> Hi Maria,
>
> On Wed, 2023-10-04 at 14:34 +0200, Anna-Maria Behnsen wrote:
>> Hi,
>> 
>> 
>
> [...]
>
>> 
>> The proper solution to this problem is to always queue the timers on
>> the
>> local CPU and allow the non pinned timers to be pulled onto a busy
>> CPU at
>> expiry time.
>
> Thanks for these patches. I am looking for saving power during video
> playback with our low power daemon. I use cgroup v2 isolation to keep
> some CPUs idle (CPU 0-11) and video is played on a single module (CPU
> 12-15).
>
> I have some kernelshark pictures at below link. The traces are
> collected with sched, timer and irq. With 6.6-rc5, you can see some
> timers still expires on CPUs which I want to keep idle. With timer
> patches added, they are mostly pulled to busy CPU. 
>
> https://imgur.com/a/8nF5OoP
>
> I can share the .dat files, but they are too big to attach here.

Thanks a lot for testing! The images are totally fine (at least for
me). As there are still some issues in v8, I'll have to post a new
version...

Thanks,

	Anna-Maria