linux-kernel - Re: [PATCH] sched: fix erroneous sysct_sched_nr

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

Message-ID: <1305018638.2914.35.camel@laptop>
Date:	Tue, 10 May 2011 11:10:38 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Vladimir Davydov <VDavydov@...allels.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Nikhil Rao <ncrao@...gle.com>, Mike Galbraith <efault@....de>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Stephan Barwolf <stephan.baerwolf@...ilmenau.de>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>
Subject: Re: [PATCH] sched: fix erroneous sysct_sched_nr_migrate logic

On Fri, 2011-05-06 at 14:02 +0400, Vladimir Davydov wrote:
> 
> But looking through the code, I found the definition: 
> 
> /*  * Number of tasks to iterate in a single balance run.  * Limited
> because this is done with IRQs disabled.  */ const_debug unsigned int
> sysctl_sched_nr_migrate = 32; 
> 
> However, AFAIS from the code, the number of tasks to iterate is
> virtually unlimited. So I conclude either the comment is confusing, or
> the logic is wrong. 
> 

Right, so I mostly agree with your (haven't actually read your patch
yet), the one worry I have is that we'll get stuck endlessly trying to
balance the first cgroup and when there's enough tasks in there but not
enough weight, we'll get stuck not making much progress.

This is one of the many things with the whole cgroup mess that needs
proper sorting out.

So yes, I agree with your interpretation of the sysctl, but I don't
think a straight fwd accounting 'fix' will actually result in a better
kernel.



--
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/