From owner-freebsd-arch Tue Feb 19 16:36:42 2002 Delivered-To: freebsd-arch@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id BEA0E37B400 for ; Tue, 19 Feb 2002 16:36:21 -0800 (PST) Received: (from dillon@localhost) by apollo.backplane.com (8.11.6/8.9.1) id g1K0a9U64733; Tue, 19 Feb 2002 16:36:09 -0800 (PST) (envelope-from dillon) Date: Tue, 19 Feb 2002 16:36:09 -0800 (PST) From: Matthew Dillon Message-Id: <200202200036.g1K0a9U64733@apollo.backplane.com> To: Jeff Roberson Cc: Julian Elischer , arch@FreeBSD.ORG Subject: Re: Prioritized bio patches. (Updated patch) References: <20020219171504.T12686-100000@mail.chesapeake.net> Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG : :First of all, I updated the patch. When I merged it in from our sources I :missed a one line change that fixed a race condition. I also changed the :priority level of NORMAL to 6 so that I could avoid all of the -1's to :index the low priority queue. : :Secondly, I ran a simple test of a kernel compile. The test system has :one disk. I did a dd of /dev/zero to a file in a users home directory :with a nice of 20 while doing a kernel compile. The original compile took :11 minutes and 32 seconds. The compile with the dd going took 15 minutes :and 12 seconds. : :I originally did this work for VOD server. The idea being that the VOD :data was guaranteed and the rest of the system would just have to wait. :... : :Jeff Jeff, this looks like really interesting stuff! Could you explain the starvation issues in more depth? e.g. if I have a nice+20 process doing disk I/O and a nice-20 process saturating the disk, is it possible for the nice-20 process to lockout the nice+20 process from doing any disk I/O? Another worry: what happens when a low priority process is holding a vnode lock while doing synchronous I/O and a high priority process wants to access the same vnode? Here I am specifically thinking about directory accesses that are incidental to a path lookup. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message