linux-kernel - Re: [PATCH 0/3] v2 Make hierarchical RCU less IPI-happy and add more tracing

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Date:	Tue, 14 Apr 2009 11:34:41 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, anton@...ba.org,
	akpm@...ux-foundation.org, dipankar@...ibm.com,
	manfred@...orfullife.com, cl@...ux-foundation.org,
	josht@...ux.vnet.ibm.com, schamp@....com, niv@...ibm.com,
	dvhltc@...ibm.com, ego@...ibm.com, laijs@...fujitsu.com,
	rostedt@...dmis.org, peterz@...radead.org, penberg@...helsinki.fi,
	andi@...stfloor.org, tglx@...utronix.de
Subject: Re: [PATCH 0/3] v2 Make hierarchical RCU less IPI-happy and add
	more tracing


* Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:

> This three-patch set fixes a hierarchical-RCU performance bug 
> located by Anton Blanchard.  This bug affects certain high-end 
> floating-point computation-heavy workloads with closely spaced 
> barrier-synchronized iterations, where an interruption of any one 
> CPU's processing during a given iteration slows the system as a 
> whole.  This bug manifests itself as excessive resched IPIs, and 
> is strictly a performance regression. It does not affect 
> correctness.
> 
> The first patch provides the fix for the problem, the second patch 
> adds the tracing, and the third patch adds the documentation for 
> the tracing.
> 
> Located-by: Anton Blanchard <anton@....ibm.com>
> Tested-by: Anton Blanchard <anton@....ibm.com>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

i've applied the first patch to tip:core/urgent (for .30) and the 
second and third one to tip:core/rcu (for .31).

Thanks Paul,

	Ingo
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