From owner-cvs-all Tue Dec 7 14: 9:41 1999 Delivered-To: cvs-all@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 0B1DC14A09; Tue, 7 Dec 1999 14:09:28 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id OAA31610; Tue, 7 Dec 1999 14:09:28 -0800 (PST) (envelope-from dillon) Date: Tue, 7 Dec 1999 14:09:28 -0800 (PST) From: Matthew Dillon Message-Id: <199912072209.OAA31610@apollo.backplane.com> To: Mike Smith Cc: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/kern kern_shutdown.c References: <199912071824.KAA02863@mass.cdrom.com> Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk :> It only issues writes for buffers that can be written out of order, :> then waits for the SCSI command to complete before issuing the :> dependancies. : :It'd be interesting to elide the wait and see if this improved :throughput. It's not (really) much of a safeguard once you assume that :disks/downstream caches are write-buffering things anyway. : :(Making that behaviour default would not be a good idea, but it'd be : interesting to see what impact it might have.) It would have no impact at all. Softupdates is an asynchronous mechanism and it is able to parallelize I/O significantly -- for example, it is fully able to commit 10 data blocks simultaniously, it is simply that it will not commit the indirect block elements pointing to those data blocks (recursively) until the data block commit has completed. I do not assume that disks/downstream caches are returning completion on the SCSI request prior to the physical write to the media (or other non-volatile storage) completing. This is totally unrelated to using ordered or unordered tags. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message