linux-kernel - Re: Slow vmalloc in 2.6.35-rc3

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Message-ID: <4C271736.5010102@redhat.com>
Date:	Sun, 27 Jun 2010 12:17:42 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Nick Piggin <npiggin@...e.de>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Slow vmalloc in 2.6.35-rc3

On 06/24/2010 06:14 PM, Nick Piggin wrote:
> On Thu, Jun 24, 2010 at 12:19:32PM +0300, Avi Kivity wrote:
>    
>> I see really slow vmalloc performance on 2.6.35-rc3:
>>      
> Can you try this patch?
> http://userweb.kernel.org/~akpm/mmotm/broken-out/mm-vmap-area-cache.patch
>    

The patch completely eliminates the problem.

>>
>> It seems completely wrong - iterating 8 levels of a binary tree
>> shouldn't take half a millisecond.
>>      
> It's not iterating down the tree, it's iterating through the
> nodes to find a free area. Slows down because lazy vunmap means
> that quite a lot of little areas build up right at the start of
> our search start address. The vmap cache should hopefully fix
> it up.
>    

I see, thanks.

-- 
error compiling committee.c: too many arguments to function

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