ZFS arc_reclaim_needed: better cooperation with pagedaemon

[Andriy Gapon]

on 23/08/2010 02:52 Artem Belevich said the following:
> Do you by any chance have a graph showing kstat.zfs.misc.arcstats.size
> behavior in addition to the stuff included on your graphs now?  

Yes, I do and not by a chance :-)

> All I
> can tell from your graphs is that v_free_count+v_cache_count shifted a
> bit lower relative to v_free_target+v_cache_min.

Don't belittle those graphs :-)
Remember that the "fuchsia" line is when pagedaemon is woken up.

> It would be
> interesting to see what effect your patch has on ARC itself,
> especially when ARC will start giving up memory and when does it stop
> shrinking.

In an extreme case it stops at arc_c_min as expected.  An extreme case is when
userland application(s) demand a lot of memory fast.

Now the graphs:
http://people.freebsd.org/~avg/arc1.png
http://people.freebsd.org/~avg/arc2.png
http://people.freebsd.org/~avg/pages.png
http://people.freebsd.org/~avg/arc3.png

What do you see?  What do you think?

-- 
Andriy Gapon