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

["Martin J. Bligh" <mbligh@mbligh.org>]

> 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?

M.

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