Date: Fri, 4 Nov 2005 09:38:33 -0800
From: Andrew Morton <akpm@osdl.org>
To: "Martin J. Bligh" <mbligh@mbligh.org>
Cc: pj@sgi.com, bron@bronze.corp.sgi.com, pbadari@gmail.com, jdike@addtoit.com,
       rob@landley.net, nickpiggin@yahoo.com.au, gh@us.ibm.com, mingo@elte.hu,
       kamezawa.hiroyu@jp.fujitsu.com, haveblue@us.ibm.com, mel@csn.ul.ie,
       kravetz@us.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
       lhms-devel@lists.sourceforge.net
Subject: Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19
Message-Id: <20051104093833.0db634f0.akpm@osdl.org>
In-Reply-To: <325200000.1131117596@[10.10.2.4]>
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"Martin J. Bligh" <mbligh@mbligh.org> wrote:
>
> > Seriously, it does appear that doing it per-task is adequate for your
> > needs, and it is certainly more general.
> > 
> > 
> > 
> > I cannot understand why you decided to count only the number of
> > direct-reclaim events, via a "digitally filtered, constant time based,
> > event frequency meter".
> > 
> > a) It loses information.  If we were to export the number of pages
> >    reclaimed from the mm, filtering can be done in userspace.
> > 
> > b) It omits reclaim performed by kswapd and by other tasks (ok, it's
> >    very cpuset-specific).
> > 
> > c) It only counts synchronous try_to_free_pages() attempts.  What if an
> >    attempt only freed pagecache, or didbn't manage to free anything?
> > 
> > d) It doesn't notice if kswapd is swapping the heck out of your
> >    not-allocating-any-memory-now process.
> > 
> > 
> > I think all the above can be addressed by exporting per-task (actually
> > per-mm) reclaim info.  (I haven't put much though into what info that
> > should be - page reclaim attempts, mmapped reclaims, swapcache reclaims,
> > etc)
> 
> I've been looking at similar things. When we page out / free something from 
> a shared library that 10 tasks have mapped, who does that count against
> for pressure?

Count pte unmappings and minor faults and account them against the
mm_struct, I guess.
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