ZFS arc_reclaim_needed: better cooperation with pagedaemon

Andriy Gapon avg at freebsd.org
Mon Aug 23 07:32:02 UTC 2010

on 23/08/2010 10:28 Artem Belevich said the following:
> If we could also deal with zone fragmentation issue you've written in
> another thread, that should bring ZFS even closer to being usable
> without shaman-style (the one with lots of muttering, swearing and
> dancing around) tuning.
> Actually, it may be worth trying your test with re-enabled UMA
> allocator for ARC. Now that pagedaemon will be running, it would also
> invoke UMA's low memory handlers and those should be able to give some
> memory back to the system.

I tried, but still no go (for my taste).
The fragmentation is too high and very significant portion of memory is
effectively lost to it.
E.g. ARC may think that it uses only 1GB but another 1GB is used by free items
in ZFS zones (of 4GB total).

Andriy Gapon

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