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

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Message-ID: <20130131112252.GB4587@gmail.com>
Date:	Thu, 31 Jan 2013 12:22:52 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
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


* 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?

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

( 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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