Date: Wed, 03 Dec 2008 15:05:50 +1100 From: Jan Mikkelsen <janm@transactionware.com> To: freebsd-stable@freebsd.org Subject: Re: 7.1-PRERELEASE: arcmsr write performance problem Message-ID: <4936059E.4050905@transactionware.com> In-Reply-To: <34C71E28-F128-4F83-80EF-75768172A59D@hiwaay.net> References: <2515BCEE3A2F4CBA8FFB9F1C052924AA@jmlaptop> <4934CB77.30906@transactionware.com> <34C71E28-F128-4F83-80EF-75768172A59D@hiwaay.net>
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David Kelly wrote: > > On Dec 1, 2008, at 11:45 PM, Jan Mikkelsen wrote: > >> Replying to my own post ... >> >> I have done a test on the same machine comparing 6.3-p1 to 7.1-PRE. >> The performance is the expected ~6MB/s (because of the lack of cache) >> on 6.3-p1, so the BIOS change doesn't seem to be at fault. >> >> This seems to be a regression somewhere between 6.3 to 7.1. The Areca >> driver is the same in 6.3 and 7.1, so the problem seems to be elsewhere. >> >> I think this is more than just a "performance" problem. The >> observations with gstat showing extremely high ms/w values (I have >> seen them as high as 22000) makes it look like IO completion >> interrupts are being lost. >> >> Any suggestions on where to look next? Are there obvious candidates? > > > ATA maximum block transfer has dropped from 128k to 64k in 7.x. Am not > sure where the handle is to tweak it back up but has slowed peak thruput > on my Dell PE400SC. Can watch with "systat -v" Interesting, thanks. > Worse, I have a stripped array of 2 drives that won't transfer more than > 43k at a chunk because apparently the stripe metadata didn't align > nicely on 64k multiples. I know the partitions start at 64kB multiples in my case. I did, however, reduce the RAID-6 stripe size to 4kB (from 64kB) and that improved things slightly, but the throughput on 7.1 is still slower by about a factor of a about 6 (measured by untaring ~3GB across ~167k files into a fresh filesystem). And on 7.1 the machine is unusable during much of the time. > -- > David Kelly N4HHE, dkelly@HiWAAY.net > ======================================================================== > Whom computers would destroy, they must first drive mad.
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