Date: Thu, 05 Jun 2008 22:53:18 +0200 From: Kris Kennaway <kris@FreeBSD.org> To: Kirk Strauser <kirk@strauser.com> Cc: freebsd-questions@freebsd.org Subject: Re: Poor read() performance, and I can't profile it Message-ID: <4848523E.2010604@FreeBSD.org> In-Reply-To: <200806051508.29424.kirk@strauser.com> References: <200806051508.29424.kirk@strauser.com>
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Kirk Strauser wrote: > I'm running a command (dumprecspg from my XBaseToPg project) on a FreeBSD 7 > server. I've noticed that throughput on that program is a lot lower than I > would have expected, and further investigation found it spending most of its > time in the kernel, presumably in read() [1]. > > I was testing the same software on my desktop PC when I noticed that it ran > *much* faster, and found that it was spending only about 1% as much time in > the kernel on Linux as it was on FreeBSD. > > I ran a quick-and-dirty comparison of the same software on two different > machines, the FreeBSD server being by far the more powerful of the two. I > ran the same command on both machines from various filesystems (to rule out > differences in drive performance), and posted the output of zsh's "time" > command for the fastest run in each setting. The results are below. > > Any ideas what could be causing this horrible performance? I'm willing to > try just about anything. ktrace(1) and check for the buffer size in use. It is probably too small. Kris
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