Date: Fri, 16 Apr 2010 08:59:21 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-fs@freebsd.org Subject: Re: kstat.zfs.misc.arcstats.hash_collisions Message-ID: <20100416065921.GH1705@garage.freebsd.pl> In-Reply-To: <4BC790FA.3040205@icyb.net.ua> References: <4BC790FA.3040205@icyb.net.ua>
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--cf0hFtnykp6aONGL Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Apr 16, 2010 at 01:19:38AM +0300, Andriy Gapon wrote: > kstat.zfs.misc.arcstats.hash_elements: 8465 > kstat.zfs.misc.arcstats.hash_elements_max: 336855 > kstat.zfs.misc.arcstats.hash_collisions: 3463061 > kstat.zfs.misc.arcstats.hash_chains: 549 > kstat.zfs.misc.arcstats.hash_chain_max: 19 >=20 > Doesn't hash_collisions value look fishy? > I haven't looked at the code yet. Perhaps stats gathering is not correct, > perhaps something else, but collisions value is really too high for my ta= ste. The hash_collisions counter is increased every time we try to add buffer to the list and something is already there. I think more important counter here is hash_chain_max, which contains maximum number of buffers on one list ever recorded. And 19 doesn't seem like a big number. --=20 Pawel Jakub Dawidek http://www.wheelsystems.com pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --cf0hFtnykp6aONGL Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iEYEARECAAYFAkvICskACgkQForvXbEpPzRJoQCfflVq/6B6I2z52bWwDO3UEAqr oiAAnRv18eYHjFvuIbpglXAc1RB704lK =culd -----END PGP SIGNATURE----- --cf0hFtnykp6aONGL--
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