Re: vfsmount lock issues on very large ppc64 box

From: Tim Chen
Date: Mon Jul 18 2011 - 12:38:56 EST

On Sat, 2011-07-16 at 19:04 -0600, Matthew Wilcox wrote:
> 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.

I've sent out a trial patch a while ago on this problem, but didn't get
a response back. Nick or Al, can you take another look at this patch now
that other folks are also running into this issue?



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