Date: Tue, 13 Mar 2001 09:17:47 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Alfred Perlstein <bright@wintelcom.net> Cc: Soren Schmidt <sos@freebsd.dk>, Kevin Oberman <oberman@es.net>, scsi@FreeBSD.ORG, gibbs@FreeBSD.ORG Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <Pine.BSF.4.21.0103130909370.2425-100000@besplex.bde.org> In-Reply-To: <20010312132922.Y18351@fw.wintelcom.net>
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On Mon, 12 Mar 2001, Alfred Perlstein wrote: > > > 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 I originally made it flush the cache if a write contained 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... :( I just put "options ATA_ENABLE_WC" in all my config files. Changing the default for write caching from enabled to disabled in rev.1.92 of ata_disk.c was a huge pessimisation, but it is probably currently required for soft updates. I don't use soft updates ... Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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