Date: Tue, 10 Jun 1997 12:52:44 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: henrich@crh.cl.msu.edu (Charles Henrich) Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Extremely poor interactive response under heave SCSI load Message-ID: <199706101752.MAA00375@dyson.iquest.net> In-Reply-To: <19970605184813.26023@crh.cl.msu.edu> from Charles Henrich at "Jun 5, 97 06:48:13 pm"
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> Has anyone else noticed that a system with a large mount of unused (hence disk > cache) ram while under heavy SCSI load (or not so heavy really, e.g: > tar tvf crh.tgz > /tmp/crh.tgz.ls) causes interactive response to go into the > toilet, and any other disk I/O takes an eternity to complete? For example, > when doing that tar tvf of a 650mb file, it took over 30 seconds for mutt to > load and run, any operation that hit disk was delayed at least 30 seconds.. > Any ideas on a rememdy/tunable for this? (Im using an adaptec 2940) > There are a couple of potential causes for the problem. I have played with versions of the vfs_bio code that reserves a certain portion of the active cache for reads. It did help. The problem with adding it to the FreeBSD code base is that it is heuristic, and it would have to withstand signficant amounts of testing before burdening the users with it (the new "feature" :-)). John
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