Date: Thu, 11 Mar 1999 14:00:01 -0800 (PST) From: "Kenneth D. Merry" <ken@plutotech.com> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/10398: Tagged queueing makes IBM DCAS-34330 slow Message-ID: <199903112200.OAA40009@freefall.freebsd.org>
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The following reply was made to PR kern/10398; it has been noted by GNATS. From: "Kenneth D. Merry" <ken@plutotech.com> To: hokada@isl.melco.co.jp (Hideaki Okada) Cc: freebsd-gnats-submit@FreeBSD.ORG Subject: Re: kern/10398: Tagged queueing makes IBM DCAS-34330 slow Date: Thu, 11 Mar 1999 14:50:22 -0700 (MST) Hideaki Okada wrote... > > Ken, > > Thanks for your support. Sorry I took so long to respond. > > So, the first thing to try is your bonnie test above, with write caching > > enabled and with write caching disabled. > > > The next thing to try is to change the number of tags on the fly and > > try to determine whether there is a point where performance drops off > > completely. > > Here are results of bonnie, measured configurations are: > WCE=1, tags=1, 2, 3, 4, 8, 16, 32, 64 > WCE=0, tags=1, 4, 16, 64 > > -------Sequential Output-------- ---Sequential Input-- --Random-- > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- > MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU > CONFIGURATION > Number of Tags > write cache enabled > NO 100 7222 89.2 6801 21.8 2347 8.5 7330 93.3 7368 14.6 226.5 4.7 > 2 100 7263 90.3 6357 20.3 2730 9.9 7025 90.5 7321 14.9 209.4 4.6 > 3 100 7115 88.1 6406 20.8 2289 8.9 7307 93.9 7335 15.0 212.6 4.5 Yeah, it looks like there is a reasonable dropoff in write performance from 1 transaction to two. It also looks like turning off write caching is a very bad thing to do with that drive. I'll put in a quirk entry to disable tagged queueing. Ken -- Kenneth Merry ken@plutotech.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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