linux-kernel - Re: [patch 3/3] sched: move sched_avg_update() to update_cpu

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:	Mon, 16 Aug 2010 10:00:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org, chris@...stnet.net,
	debian00@...ceadsl.fr, hpa@...or.com, jonathan.protzenko@...il.com,
	mans@...sr.com, psastudio@...l.ru, rjw@...k.pl,
	stephan.eicher@....de, sxxe@....de, thomas@...hlinux.org,
	venki@...gle.com, wonghow@...il.com
Subject: Re: [patch 3/3] sched: move sched_avg_update() to update_cpu_load()

On Fri, 2010-08-13 at 12:45 -0700, Suresh Siddha wrote:
> plain text document attachment (move_sched_avg_update.patch)
> Currently sched_avg_update() (which updates rt_avg stats in the rq) is getting
> called from scale_rt_power() (in the load balance context) which doesn't take
> rq->lock.

Right, but I think it doesn't need to, as its never accessed cross CPU
(except maybe for /proc/sched_debug, and who cares about that).

The (other) odd case is NO_HZ idle balancing, but there the actual CPU
won't be updating the fields, so the remote CPU doing NO_HZ idle
balancing should be good to touch it.

> Fix it by moving the sched_avg_update() to more appropriate update_cpu_load()
> where the CFS load gets updated aswell.

Right, except it breaks things a bit, at the very least you really need
that update right before reading it, otherwise you can end up with >100%
fractions, which are odd indeed ;-)


--
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/