linux-kernel - Re: [PATCH 0/2] RFC: readd fair sleepers for server systems

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]

Date:	Wed, 23 May 2012 13:49:58 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Christian Ehrhardt <ehrhardt@...ux.vnet.ibm.com>
Cc:	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...nel.org>, Mike Galbraith <efault@....de>,
	linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 0/2] RFC: readd fair sleepers for server systems

On Wed, 2012-05-23 at 13:32 +0200, Christian Ehrhardt wrote:
> > Why is this, is this some weird interaction with your hypervisor?
> 
> It is not completely analyzed, as soon as debugging goes out of Linux it 
> can be kind of complex even internally. 

Is there significant steal time in these workloads? If so, does it help
if you implement
CONFIG_PARAVIRT_TIME_ACCOUNTING/paravirt_steal_rq_enabled for s390?
(although I guess we'd better loose the paravirt part of the name then).

This 'feature' subtracts steal time from the task-clock so that the
scheduler doesn't consider a task to be running when the vcpu wasn't
running as well.

Not doing that (current situation) could result in over-active
preemption because we think a task ran significantly longer than it
actually did. Same for sleeper fairness, we might think a task slept
very long (and give a bigger boost) when in fact it didn't.

--
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/