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

Martin J. Bligh
2005-11-04T15:19:56Z

> 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.