Subject: Re: [patch] latency tracer, 2.6.15-rc7
From: Lee Revell <rlrevell@joe-job.com>
To: paulmck@us.ibm.com
Cc: Linus Torvalds <torvalds@osdl.org>, Ingo Molnar <mingo@elte.hu>,
       Dave Jones <davej@redhat.com>, Hugh Dickins <hugh@veritas.com>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       Eric Dumazet <dada1@cosmosbay.com>,
       Dipankar Sarma <dipankar@in.ibm.com>
In-Reply-To: <20051231042902.GA3428@us.ibm.com>
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	 <1135908980.4568.10.camel@mindpipe> <20051230080032.GA26152@elte.hu>
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	 <Pine.LNX.4.64.0512301701320.3249@g5.osdl.org>
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	 <Pine.LNX.4.64.0512301726190.3249@g5.osdl.org>
	 <1136001615.3050.5.camel@mindpipe>  <20051231042902.GA3428@us.ibm.com>
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Date: Fri, 30 Dec 2005 23:54:14 -0500
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On Fri, 2005-12-30 at 20:29 -0800, Paul E. McKenney wrote:
> This should help in UP configurations, or in SMP configurations where
> all CPUs are doing call_rcu_bh() very frequently.  I would not expect
> it to help in cases where one of several CPUs is frequently executing
> call_rcu_bh(), but where the other CPUs are either CPU-bound in user
> space or are in a tickful idle state. 

This and net/decnet/dn_route.c are the only two uses of call_rcu_bh in
the kernel.  And this one does not seem to be invoked frequently, it
took ~48 hours to show up in the latency tracer.  Of course a server
workload might call it all the time.

Lee

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