Date: Wed, 30 Sep 2009 08:30:34 +0200 From: Attilio Rao <attilio@freebsd.org> To: Dieter <freebsd@sopwith.solgatos.com> Cc: freebsd-performance@freebsd.org Subject: Re: A specific example of a disk i/o problem (was: FreeBSD vs Ubuntu) Message-ID: <3bbf2fe10909292330t753bcad1r69ae67d7e898ee35@mail.gmail.com> In-Reply-To: <200909300226.CAA29195@sopwith.solgatos.com> References: <cone.1254242533.271161.79872.1000@zoraida.natserv.net> <200909300226.CAA29195@sopwith.solgatos.com>
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2009/9/30 Dieter <freebsd@sopwith.solgatos.com>: >> > My question is why is FreeBSD's disk i/o performance so bad? >> >> As I mentioned... this was discussed actively in slashdot. You will find >> there many good comments on this. > > All I saw in slashdot was a ffs vs ext comment. I don't believe the problems > I'm seeing are filesystem related. > >> > Not just in the benchmarks with debugging on, but in real world usage >> > where it actually matters. >> >> Are you saying this from actual experience or from reading other people's >> comments? > > Here is a specific demo of one disk i/o problem I'm seeing. Should be > easy to reproduce? > > http://lists.freebsd.org/pipermail/freebsd-performance/2008-July/003533.html > > This was over a year ago, so add 7.1 to the list of versions with the problem. > I believe that the > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 1148109, size: 4096 > messages I'm getting are the same problem. A user process is hogging > the bottleneck (disk buffer cache?) and the swapper/pager is getting starved. Sorry, do you have a PR/describing e-mail with this issue? Can you be a bit more precise? The problem reported in the earlier post, however, is interesting and worths more analysis. More speficially, would you be interested in reproducing and playing a bit with some diagnostic tool/configurations I can point you at? Attilio -- Peace can only be achieved by understanding - A. Einstein
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