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Date: Wed, 11 May 2011 15:53:24 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Valdis.Kletnieks@vt.edu, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: mmotm 2011-04-29 - wonky VmRSS and VmHWM values after swapping
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On Tue, 10 May 2011 18:04:45 +0200
Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> > hm, me too.  After boot, hald has a get_mm_counter(mm, MM_ANONPAGES) of
> > 0xffffffffffff3c27.  Bisected to Pater's
> > mm-extended-batches-for-generic-mmu_gather.patch, can't see how it did
> > that.
> > 
> 
> I haven't quite figured out how to reproduce, but does the below cure
> things? If so, it should probably be folded into the first patch
> (mm-mmu_gather-rework.patch?) since that is the one introducing this.
> 
> ---
> Subject: mm: Fix RSS zap_pte_range() accounting
> 
> Since we update the RSS counters when breaking out of the loop and
> release the PTE lock, we should start with fresh deltas when we
> restart the gather loop.
> 
> Reported-by: Valdis.Kletnieks@vt.edu
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> Index: linux-2.6/mm/memory.c
> ===================================================================
> --- linux-2.6.orig/mm/memory.c
> +++ linux-2.6/mm/memory.c
> @@ -1120,8 +1120,8 @@ static unsigned long zap_pte_range(struc
>  	spinlock_t *ptl;
>  	pte_t *pte;
>  
> -	init_rss_vec(rss);
>  again:
> +	init_rss_vec(rss);
>  	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
>  	arch_enter_lazy_mmu_mode();
>  	do {

That fixed the negative hald VmHWM output on my test box.