Date: Thu, 05 Jun 2008 18:23:39 -0500 From: Kirk Strauser <kirk@strauser.com> To: Kris Kennaway <kris@FreeBSD.org> Cc: freebsd-questions@freebsd.org Subject: Re: Poor read() performance, and I can't profile it Message-ID: <4848757B.30408@strauser.com> In-Reply-To: <484867E3.3070705@FreeBSD.org> References: <200806051508.29424.kirk@strauser.com> <4848523E.2010604@FreeBSD.org> <200806051617.54400.kirk@strauser.com> <484867E3.3070705@FreeBSD.org>
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Kris Kennaway wrote: > No, if it's reading in 16 byte units it will explain the terrible > performance. No, it's actually doing 4096-byte reads. That was just an example of what I meant. Since I wrote that, though, I wrote a program to do 1,000,000 seeks to position 0, and it ran immeasurably fast. I'm guessing that lseek() is optimized to not do anything if you ask it to move to the position you're already at. Any other thoughts? There definitely aren't any setbuf() calls, and no matter what it still takes 100 times more kernel overhead on Linux than FreeBSD. Speaking of which, I think my next experiment will be to try the Linux binaries on FreeBSD and see if it behaves similarly. -- Kirk Strauser
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