Date: Mon, 12 Mar 2001 13:29:22 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: Soren Schmidt <sos@freebsd.dk> Cc: Kevin Oberman <oberman@es.net>, scsi@FreeBSD.ORG, gibbs@FreeBSD.ORG Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <20010312132922.Y18351@fw.wintelcom.net> In-Reply-To: <200103122120.WAA10675@freebsd.dk>; from sos@freebsd.dk on Mon, Mar 12, 2001 at 10:20:32PM %2B0100 References: <20010312125905.X18351@fw.wintelcom.net> <200103122120.WAA10675@freebsd.dk>
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Moved to -scsi... Justin, as Mr. SCSI (can i call you that? :) ) I'd like to ask you something * Soren Schmidt <sos@freebsd.dk> [010312 13:20] wrote: > It seems Alfred Perlstein wrote: > > > > Prior to March 1 I could dd a 4 GB slice in 580 seconds (or a bit > > > > under 10 minutes). After March 1 the same exact command took just > > > > under 40 minutes to complete. The same was seen copying a 2 GB > > > > slice. It increased from 5 minutes to 20 minutes. No kernel > > > > configuration changes were made. > > > > > > This is worse than expected, try to use option ATA_ENABLE_WC > > > and see what gives, if its not back to normal we have to look elsewhere. > > > > Mr ATA, is there no ATA command to "syncronize cache" like in SCSI? > > Yes, there is, and the ATA driver even uses it, the problem is WHEN > to use it. I originally made it flush the cache if a write contained > the BIO_ORDERED bit, but that doesn't work with softupdates.. > If somebody can come up with a way to tell me when I need to flush > the write cache, then I'll happily add that.. Justin, I've heard that SCSI knows when to send sync-cache commands to the disks, how does the driver know when to do this based on the bio request? It'd be nice to get this fixed for 4.3 because I've noticed terrible perf for laptops because of the complete lack of write caching... :( -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] Daemon News Magazine in your snail-mail! http://magazine.daemonnews.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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