linux-kernel - Re: vfsmount lock issues on very large ppc64 box

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Date:	Sat, 16 Jul 2011 19:04:28 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Anton Blanchard <anton@...ba.org>
Cc:	npiggin@...nel.dk, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: vfsmount lock issues on very large ppc64 box

On Sun, Jul 17, 2011 at 10:50:27AM +1000, Anton Blanchard wrote:
> Looking closer, all of these calls are in pipefs and sockfs.
> Since we never mount either filesystem they never get a long term
> reference and we always end up in the very slow write brlock path
> that takes a lock for each online CPU.
> 
> Here is a quick hack that takes a long term reference on pipefs
> and sockfs which fixes the problem. Any thoughts on how we should
> fix it properly?

I know Tim and Andi have been looking into this ... I forget what their
fix was though.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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