From owner-freebsd-questions@FreeBSD.ORG Fri Jan 18 10:28:19 2013 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 96199AD9 for ; Fri, 18 Jan 2013 10:28:19 +0000 (UTC) (envelope-from freebsd-listen@fabiankeil.de) Received: from smtprelay06.ispgateway.de (smtprelay06.ispgateway.de [80.67.31.104]) by mx1.freebsd.org (Postfix) with ESMTP id 2C2F6D60 for ; Fri, 18 Jan 2013 10:28:19 +0000 (UTC) Received: from [78.35.163.76] (helo=fabiankeil.de) by smtprelay06.ispgateway.de with esmtpsa (SSLv3:AES128-SHA:128) (Exim 4.68) (envelope-from ) id 1Tw9BD-00009a-IZ; Fri, 18 Jan 2013 11:28:11 +0100 Date: Fri, 18 Jan 2013 11:20:10 +0100 From: Fabian Keil To: Eitan Adler Subject: Re: absurd I/O perf with ZFS: hangs on zfs->cv) Message-ID: <20130118112010.43ad3edb@fabiankeil.de> In-Reply-To: References: <20130117135241.434f273a@fabiankeil.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/KOxxjH47ShGJSOjGAqyLVRE"; protocol="application/pgp-signature" X-Df-Sender: Nzc1MDY3 Cc: questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Jan 2013 10:28:19 -0000 --Sig_/KOxxjH47ShGJSOjGAqyLVRE Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Eitan Adler wrote: > On 17 January 2013 07:52, Fabian Keil wrot= e: > > Eitan Adler wrote: > > I don't think there are any laptops with "large amounts of RAM" > > as far as ZFS is concerned. >=20 > Haha okay: 8GB of RAM. >=20 > >> It is taking me 45 minutes to make 5 commits to git. Something is > >> wrong here but I have no idea what I should be looking at. Any ideas? > > > > Try sysutils/zfs-stats to get a rough idea of how ZFS is using > > the available memory. >=20 > Anything in particular I should be looking for? I mainly look at the "ARC Summary" and the "ARC Efficiency" sections but I suppose all the information is useful in some situations. =20 > > If you already followed tuning advice from the Internet without > > benchmarking it, try reverting it. >=20 > I have done absolutely no tuning. Is there anything in particular I > *should* tune? A common recommendation is to disable atime for all datasets where it isn't needed as it can cause lots of unnecessary write operations. With 8 GB of RAM ZFS enables prefetching by default and I assume for the git use case it's not too useful and could hurt performance by amplifying read operations. The "Data Prefetch Efficiency" is shown by zfs-stats and if it doesn't look too impressive you might want to disable prefetching to see if it helps. If your repository isn't fresh, you could also try "git gc". My impression is that the automatic doesn't trigger frequently enough for larger repositories like /usr/src. Fabian --Sig_/KOxxjH47ShGJSOjGAqyLVRE Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iEYEARECAAYFAlD5Id0ACgkQBYqIVf93VJ1ELwCfVP+RUz5XjQauFAHqo4koPBBd nSMAoIAzDy4fhg4YoKEz1ptD4E+nUnya =HDOq -----END PGP SIGNATURE----- --Sig_/KOxxjH47ShGJSOjGAqyLVRE--