From owner-freebsd-fs@FreeBSD.ORG Fri Apr 16 06:59:26 2010 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 41C0B1065677 for ; Fri, 16 Apr 2010 06:59:26 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: from mail.garage.freebsd.pl (chello089077043238.chello.pl [89.77.43.238]) by mx1.freebsd.org (Postfix) with ESMTP id 856798FC21 for ; Fri, 16 Apr 2010 06:59:25 +0000 (UTC) Received: by mail.garage.freebsd.pl (Postfix, from userid 65534) id 4940945CD9; Fri, 16 Apr 2010 08:59:24 +0200 (CEST) Received: from localhost (chello089077043238.chello.pl [89.77.43.238]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.garage.freebsd.pl (Postfix) with ESMTP id 1D93F45E90; Fri, 16 Apr 2010 08:59:19 +0200 (CEST) Date: Fri, 16 Apr 2010 08:59:21 +0200 From: Pawel Jakub Dawidek To: Andriy Gapon Message-ID: <20100416065921.GH1705@garage.freebsd.pl> References: <4BC790FA.3040205@icyb.net.ua> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="cf0hFtnykp6aONGL" Content-Disposition: inline In-Reply-To: <4BC790FA.3040205@icyb.net.ua> User-Agent: Mutt/1.4.2.3i X-PGP-Key-URL: http://people.freebsd.org/~pjd/pjd.asc X-OS: FreeBSD 9.0-CURRENT i386 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mail.garage.freebsd.pl X-Spam-Level: X-Spam-Status: No, score=-0.6 required=4.5 tests=BAYES_00,RCVD_IN_SORBS_DUL autolearn=no version=3.0.4 Cc: freebsd-fs@freebsd.org Subject: Re: kstat.zfs.misc.arcstats.hash_collisions X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Apr 2010 06:59:26 -0000 --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--