[CFT] ZFS v15 patch (version 3)

Peter Jeremy peterjeremy at acm.org
Fri Jul 9 23:22:17 UTC 2010

On 2010-Jul-08 23:30:33 +0200, Martin Matuska <mm at FreeBSD.org> wrote:
>> Looking at the patchset, the most critical issue (IMHO) that doesn't
>> appear to have been addressed is the interaction between ZFS ARC and
>> the VM cache used by UFS/NFS: arc_memory_throttle() is still making
>> decisions solely on the amount of "free" memory, without considering
>> "inactive" or "cache".  I am running a slight variant of a patch by
>Regarding ARC, you might want to try the revision 209227 from head that
>is scheduled for MFC on 18.7.2010:

That patch appears to address issues with unreasonable arc sizing but
doesn't alter the throttling algorithm: FreeBSD's "traditional" VM
management algorithm (used by everything except ZFS) minimises space
marked as "free" by preferentially keeping cached data in the "cache"
or "inactive" queues.  ZFS uses its own caching which solely uses the
"free" list to determine memory availability.  This means ZFS can't
apply any pressure to the FreeBSD VM system and runs in a virtually
permanent state of memory starvation.

In any case, I have applied that patch as it appears useful.

Peter Jeremy
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