linux-kernel - Re: CPU scheduler question/problem

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: <1232725219.4826.131.camel@laptop>
Date:	Fri, 23 Jan 2009 16:40:19 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Pawel Dziekonski <dzieko@...il.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: CPU scheduler question/problem

On Thu, 2009-01-22 at 22:34 +0100, Pawel Dziekonski wrote:
> question: is there a way to better balance processes over different
> cores and do it automagically?

Hard, the load-balancing code is a bunch of heuristics that work 'well'
for most of the things.

The pipe workload you mentioned has would behave that way because pipes
'assume' a produces/consumer behaviour, and thus are more likely to
place both tasks on the same cpu -- but will eventually pull them apart
if they want to run concurrently.

You might enable SCHED_DEBUG=y and try

 echo NO_SYNC_WAKEUPS > /debug/sched_features

For that particular load.

About your quantum chemistry application -- you say they share a
workload, does that mean they synchronize a lot on locks? If so, the
scheduler might, at times of serialization, think it is a
produces/consumer load and move tasks together, and then later, when
they run independently, move them apart again.

I'm afraid you'll have to share a bit more of how your application works
in order to get a more informed answer.

--
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/