linux-kernel - Re: [RFC -v3 PATCH 2/3] sched: add yield

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] [day] [month] [year] [list]

Message-ID: <4D2E88EA.3050604@redhat.com>
Date:	Thu, 13 Jan 2011 00:08:58 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mike Galbraith <efault@....de>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Avi Kiviti <avi@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [RFC -v3 PATCH 2/3] sched: add yield_to function

On 01/12/2011 10:26 PM, Mike Galbraith wrote:
> On Wed, 2011-01-12 at 22:02 -0500, Rik van Riel wrote:
>
>> Cgroups only makes the matter worse - libvirt places
>> each KVM guest into its own cgroup, so a VCPU will
>> generally always be alone on its own per-cgroup, per-cpu
>> runqueue!  That can lead to pulling a VCPU onto our local
>> CPU because we think we are alone, when in reality we
>> share the CPU with others...
>
> How can that happen?  If the task you're trying to accelerate isn't in
> your task group, the whole attempt should be a noop.

Nono, all the VCPUs from the same guest are in the same
cgroup.  However, with 4 VCPUs and 4 physical CPUs,
chances are that they're all alone on their own per-cpu,
per-cgroup cfs_rq.

However, each CPU might have other runnable processes in
other cfs_rq sched entities.

-- 
All rights reversed
--
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/