svn commit: r351673 - in head: lib/libmemstat share/man/man9 sys/cddl/compat/opensolaris/kern sys/kern sys/vm

[Andriy Gapon]

On 04/09/2019 01:01, Mark Johnston wrote:
> Some of the vm_lowmem eventhandlers probably shouldn't be called each
> time the page daemon scans the inactive queue (every 0.1s under memory
> pressure).  ufsdirhash_lowmem and mb_reclaim in particular don't seem
> like they need to be invoked very frequently.  We could easily define
> multiple eventhandlers to differentiate between these cases, though.

My proposal is to run uma_reclaim(UMA_RECLAIM_TRIM) before invoking vm_lowmem.
If that reclaims "enough" memory, then do not call vm_lowmem at all.

Oh, and I have a related question.
Say, a zone has X items in use and Y items in cache.
After running vm_lowmem the composition changes to X - C and Y + C respectively.
Then we run uma_reclaim(UMA_RECLAIM_TRIM).
Question: is that guaranteed to free at least C items?
I am thinking about a possibility that the zone's workset size is estimated to
be at least X (and maybe even more than X + Y).  In that case UMA_RECLAIM_TRIM
won't free those C items, they will stay in the cache.  So, it seems like
releasing them was in vain, at least for the immediate reclaim.

-- 
Andriy Gapon