linux-kernel - Re: [tip:sched/core] sched: Add 'autogroup' scheduling feature: automated per session task groups

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: <AANLkTi=3-FpuzXZ8xoEWCPhKrwydDOj0m4n-eEh-2BdT@mail.gmail.com>
Date:	Mon, 20 Dec 2010 21:16:47 +0530
From:	Bharata B Rao <bharata.rao@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	mathieu.desnoyers@...icios.com, torvalds@...ux-foundation.org,
	efault@....de, pjt@...gle.com, markus@...ppelsdorf.de,
	tglx@...utronix.de, oleg@...hat.com, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched: Add 'autogroup' scheduling feature:
 automated per session task groups

On Mon, Dec 20, 2010 at 6:49 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> On Mon, 2010-12-20 at 18:38 +0530, Bharata B Rao wrote:
>> The autogroup patchset removes the display of cgroup name from
>> sched_debug output.
>
> Hrmph.. that wasn't supposed to happen, care to send a patch to fix that
> up?

There are two aspects here:

- Printing cgroup name for per-CPU cfs_rqs shouldn't be affected by
  autogroup and the old code should work here.
- Printing cgroup name for tasks depends on task_group(), which has
been changed by autogroup patch. I haven't really looked deep into
autogroup patch, but from whatever I can gather, Mike had a reason
to remove this bit from sched_debug. The task groups created for
autogroups don't have cgroups associated with them and hence no
dentries and hence no pathnames.

I guess we could do fix this as shown in the attached patch.

>
>
>> Also, with tg_shares_up improvements, the leaf cfs_rqs are maintained
>> on rq->leaf_cfs_rq_list only if they carry any load. But the code to
>> display cfs_rq information for sched_debug isn't updated and hence
>> information from a few cfs_rqs are missing from sched_debug.
>
> Well, that's a _good_ thing, right?
>
> I mean, if we know they're empty, and don't contribute to schedule, why
> bother displaying them?

In addition to tasks, we do display other details pertaining to the cfs_rq.
I thought, having a complete view of all the cfs_rqs in the system would
be better and consistent than obtaining different cfs_rqs on different
captures of /proc/sched_debug.

Regards,
Bharata.
-- 
http://bharata.sulekha.com/blog/posts.htm, http://raobharata.wordpress.com/

Download attachment "fix-sched-debug.patch" of type "application/octet-stream" (2636 bytes)