linux-kernel - Re: missing madvise functionality

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Date:	Thu, 05 Apr 2007 12:01:03 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Eric Dumazet <dada1@...mosbay.com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jakub Jelinek <jakub@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Rik van Riel <riel@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Hugh Dickins <hugh@...itas.com>
Subject: Re: missing madvise functionality

Eric Dumazet wrote:
> On Wed, 04 Apr 2007 20:05:54 +1000
> Nick Piggin <nickpiggin@...oo.com.au> wrote:
> 
>>>@@ -1638,7 +1652,7 @@ find_extend_vma(struct mm_struct * mm, u
>>> 	unsigned long start;
>>> 
>>> 	addr &= PAGE_MASK;
>>>-	vma = find_vma(mm,addr);
>>>+	vma = find_vma(mm,addr,&current->vmacache);
>>> 	if (!vma)
>>> 		return NULL;
>>> 	if (vma->vm_start <= addr)
>>
>>So now you can have current calling find_extend_vma on someone else's mm
>>but using their cache. So you're going to return current's vma, or current
>>is going to get one of mm's vmas in its cache :P
> 
> 
> This was not a working patch, just to throw the idea, since the answers I got showed I was not understood.
> 
> In this case, find_extend_vma() should of course have one struct vm_area_cache * argument, like find_vma()
> 
> One single cache on one mm is not scalable. oprofile badly hits it on a dual cpu config.

Oh, what sort of workload are you using to show this? The only reason that I
didn't submit my thread cache patches was that I didn't show a big enough
improvement.

-- 
SUSE Labs, Novell Inc.
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