linux-kernel - Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat

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Message-ID: <87hbxwj1k3.fsf@basil.nowhere.org>
Date:	Wed, 01 Jul 2009 09:38:04 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC] Adding information of counts processes acquired how many spinlocks to schedstat

Hitoshi Mitake <mitake@....info.waseda.ac.jp> writes:

> Hi,
>
> I wrote a test patch which add information of counts processes acquired how many spinlocks to schedstat.
> After applied this patch, /proc/<PID>/sched will change like this,

The problem is that spinlocks are very common and schedstats is enabled commonly
in production kernels. You would need to demonstrate that such a change doesn't
have significant performance impact. For me it looks like it has.

Also I'm not sure exactly what good such a metric is. Do you have 
a concrete use case?

The normal way to check for lock contention or lock bouncingis to
simply profile cycles or time and see if there is a lot of CPU time in
locks.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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