linux-kernel - Re: aim7 performance regression by commit 5a50508 report from LKP

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Date:	Fri, 1 Feb 2013 18:53:13 +0800
From:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Huang Ying <ying.huang@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	linux-kernel@...r.kernel.org, lkp@...ux.intel.com
Subject: Re: aim7 performance regression by commit 5a50508 report from LKP

On Thu, Jan 31, 2013 at 12:22:52PM +0100, Ingo Molnar wrote:
> 
> * Yuanhan Liu <yuanhan.liu@...ux.intel.com> wrote:
> 
> > > or whether the lock hold times could be reduced drastically
> > 
> > I also found one, but it doesn't sound like the one will 
> > reduce lock hold times drastically:
> >
> >    vma_lock_anon_vma() seems covered too much code at
> >    expand_up/downwards.
> > 
> > Well, again, it's quite a tiny optimization for reducing the 
> > coverage.
> 
> The fundamental problem is I think that there's a single anon 
> vma lock for the whole workload, right?

Yes.
> 
> Is that really fundamentally needed, could that be spread out 
> perhaps?

I'm digging into this. 

Thanks.

	--yliu
> 
> ( But first we want to see how much of the regression we can fix 
>   in an equivalent-locking-patterns fashion - improving locking
>   is a separate matter. )
> 
> Thanks,
> 
> 	Ingo
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