linux-kernel - Re: [PATCH V2 3/3] workqueue: Schedule work on non-idle cpu instead of current one

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAKohpokdhtB0bx2xyoMXXTW2O499X_y4Yg_wmqKM82rxK2-u=Q@mail.gmail.com>
Date:	Mon, 1 Oct 2012 09:17:28 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	vincent.guittot@...aro.org, Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, pjt@...gle.com,
	paul.mckenney@...aro.org, tglx@...utronix.de,
	suresh.b.siddha@...el.com, venki@...gle.com, mingo@...hat.com,
	peterz@...radead.org, robin.randhawa@....com,
	Steve.Bannister@....com, Arvind.Chauhan@....com,
	amit.kucheria@...aro.org, linaro-dev@...ts.linaro.org,
	patches@...aro.org
Subject: Re: [PATCH V2 3/3] workqueue: Schedule work on non-idle cpu instead
 of current one

On 1 October 2012 06:02, Tejun Heo <tj@...nel.org> wrote:
> It isn't about the CPU being actually idle?

No. Being idle only from scheduler's perspective. :)

> Also, if it's only about timers, shouldn't it be enough to implement
> it for timer and delayed_work?

What if we need a timer, which must re-arm itself + schedule a work?
delayed_work will not be sufficient in that case, and we would need
to use normal work.

If i am not wrong, there can be other future users of this routine too.
@Vincent: Can you please comment on this?

> It would be great if you explain what you're trying to achieve how.  I
> can't tell what you're aiming for and why that would be beneficial
> from these submissions.

Following slides are implemented by Vincent and presented during LPC.
Please have a look at them, they explain the problem statement well:

http://www.linuxplumbersconf.org/2012/wp-content/uploads/2012/08/lpc2012-sched-timer-workqueue.pdf

Specifically slides: 12 & 19.

There aren't too many users with this behavior, but even a single user
will be sufficient not to let the cpu get idle at all. And that will result in
less power saving.

--
viresh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/