From owner-freebsd-fs  Sat Apr  1 17: 3:39 2000
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Date: Sat, 1 Apr 2000 17:03:24 -0800 (PST)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <200004020103.RAA43602@apollo.backplane.com>
To: Richard Wendland <richard@netcraft.com>
Cc: Paul Richards <paul@originative.co.uk>,
	Alfred Perlstein <bright@wintelcom.net>,
	Poul-Henning Kamp <phk@critter.freebsd.dk>, current@FreeBSD.ORG,
	fs@FreeBSD.ORG
Subject: Re: FreeBSD random I/O performance issues
References:  <200003221544.PAA08760@ns0.netcraft.com>
Sender: owner-freebsd-fs@FreeBSD.ORG
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X-Loop: FreeBSD.org

    I've committed an 80% fix for the random seek / write
    performance issue.  The rest of the fix will come later
    when Kirk commits his shared-lock-buffer-cache idea.

    I've committed it into -current and will MFC it into
    -stable in a week if there aren't any problems.  I
    do not intend to MFC it into 3.x.

    This should solve most of the random-I/O latency issues
    with read-after-write on buffers.  Basically what
    had to be done was to continue to call the clustering
    code as before (so reallocblks still gets called), but 
    only issue write_behind I/O if the writes are
    generally sequential.  If the writes are random, even 
    big writes, we do not issue write-behind I/O.

				    -Matt



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