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Date: Mon, 7 Oct 2013 19:25:23 +0200
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Subject: Re: Call fo comments - raising vfs.ufs.dirhash_reclaimage?
From: Davide Italiano <davide@freebsd.org>
To: Ivan Voras <ivoras@freebsd.org>
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Cc: freebsd-fs@freebsd.org, FreeBSD Hackers <freebsd-hackers@freebsd.org>
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On Wed, Aug 28, 2013 at 3:56 PM, Ivan Voras <ivoras@freebsd.org> wrote:
> Hi,
>
> Prodded by davide@, I'd like to collect opinions about raising the
> vfs.ufs.dirhash_reclaimage sysctl from 5 to 60, committed at:
>
> http://svnweb.freebsd.org/changeset/base/254986
>
> What it does:
>
> Used in lowmem handler at
> http://fxr.watson.org/fxr/source/ufs/ufs/ufs_dirhash.c#L1247 when
> determining which cache entries to evict; it skips (keeps in the cache)
> entries which are younger than this number of seconds. This lowmem
> handler only frees up to 10% of the dirhash cache at a time.
>

I don't think this is correct. The first loop scans over the whole
ufsdirhash_list and there's nothing that sets the cap to 10%.
It might happen that UFS is unused for some minutes and you'll end up
with all the cache free'd.

-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare