linux-kernel - Re: [PATCH] sched: fix env->src

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Message-ID: <20130213140843.GA21308@brouette>
Date:	Wed, 13 Feb 2013 15:08:43 +0100
From:	Damien Wyart <damien.wyart@...il.com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linaro-dev@...ts.linaro.org,
	peterz@...radead.org, mingo@...nel.org,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] sched: fix env->src_cpu for active migration

* Vincent Guittot <vincent.guittot@...aro.org> [2013-02-13 13:08]:
> Damien,
> Regarding your sched_domain config and especially the flags field, you
> should not be impacted by my patch because
> - need_active_balance is the only new place that use env->src_cpu in
> the load_balance function
> - and your machine will never test the condition: "env->src_cpu >
> env->dst_cpu" in need_active_balance because  SD_ASYM_PACKING is not
> set in your config

> Have you tested the patch with others that could have modified the
> load_balance function ?

Yes, sorry, I should have been more precise in my initial report: your
patch was not applied on top of vanilla 3.8-rc7, but a few other patches
were also present. Seems the ones impacting load_balance are from
Frederic's nohz work
(http://git.kernel.org/?p=linux/kernel/git/frederic/linux-dynticks.git;a=shortlog;h=refs/heads/3.8-rc6-nohz4)

The patches from there modifying load_balance are:
- "sched: Update nohz rq clock before searching busiest group on load balancing"
- "sched: Update clock of nohz busiest rq before balancing"

In this test, I did not use any kernel parameter related to this
patchset (full_nohz, etc.).

I am adding Frederic in Cc, not sure if the breakage is to be
investigated on your side or his...


Thanks for your explanations,
-- 
Damien
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