Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

[Andrew Morton <akpm@osdl.org>]

"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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