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Date: Thu, 05 Apr 2007 12:01:03 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Eric Dumazet <dada1@cosmosbay.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Andrew Morton <akpm@linux-foundation.org>,
       Jakub Jelinek <jakub@redhat.com>, Ulrich Drepper <drepper@redhat.com>,
       Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
       Hugh Dickins <hugh@veritas.com>
Subject: Re: missing madvise functionality
References: <46128051.9000609@redhat.com>	<p73648dz5oa.fsf@bingen.suse.de>	<46128CC2.9090809@redhat.com>	<20070403172841.GB23689@one.firstfloor.org>	<20070403125903.3e8577f4.akpm@linux-foundation.org>	<4612B645.7030902@redhat.com>	<20070403202937.GE355@devserv.devel.redhat.com>	<20070403144948.fe8eede6.akpm@linux-foundation.org>	<4612DCC6.7000504@cosmosbay.com>	<46130BC8.9050905@yahoo.com.au>	<1175675146.6483.26.camel@twins>	<461367F6.10705@yahoo.com.au>	<20070404113447.17ccbefa.dada1@cosmosbay.com>	<46137882.6050708@yahoo.com.au> <20070404135458.4f1a7059.dada1@cosmosbay.com>
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Eric Dumazet wrote:
> On Wed, 04 Apr 2007 20:05:54 +1000
> Nick Piggin <nickpiggin@yahoo.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.