Date: Mon, 22 Nov 2004 16:08:11 +0100 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: des@des.no (=?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?=) Cc: arch@freebsd.org Subject: Re: anticipatory I/O scheduling Message-ID: <24318.1101136091@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 22 Nov 2004 15:12:51 %2B0100." <xzpu0rigefw.fsf@dwp.des.no>
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In message <xzpu0rigefw.fsf@dwp.des.no>, =?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?= writes: >I just ran across this paper and started wondering why I'd never heard >of it before: > ><URL:http://www.cs.rice.edu/~ssiyer/r/antsched/>; > >To summarize, the authors rewrote the I/O scheduling algorithm in >FreeBSD 4.3 and got massive performance improvements for Apache, and >smaller but noticeable improvements for AFS and TPC-B. > >Has anyone looked into this? Yes. It's very hard to implement it correctly because you need a very rapid timer (order of microseconds). It is my plan to make disksort algorithms changeable on a per disk basis to encourage experimentation in this area. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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