From owner-freebsd-current Tue Apr 17 14:42:15 2001 Delivered-To: freebsd-current@freebsd.org Received: from netbank.com.br (garrincha.netbank.com.br [200.203.199.88]) by hub.freebsd.org (Postfix) with ESMTP id ABB8437B43E for ; Tue, 17 Apr 2001 14:42:10 -0700 (PDT) (envelope-from riel@conectiva.com.br) Received: from surriel.ddts.net (1-114.cwb-adsl.brasiltelecom.net.br [200.193.160.114]) by netbank.com.br (Postfix) with ESMTP id 49C394681A; Tue, 17 Apr 2001 18:42:51 -0300 (BRST) Received: from localhost (svxqxb@localhost [127.0.0.1]) by surriel.ddts.net (8.11.2/8.11.2) with ESMTP id f3HLf0f27197; Tue, 17 Apr 2001 18:41:10 -0300 Date: Tue, 17 Apr 2001 18:41:00 -0300 (BRST) From: Rik van Riel X-Sender: riel@imladris.rielhome.conectiva To: Matt Dillon Cc: Alfred Perlstein , "Justin T. Gibbs" , Doug Barton , "'current@freebsd.org'" Subject: Re: FW: Filesystem gets a huge performance boost In-Reply-To: <200104172107.f3HL7ei07632@earth.backplane.com> Message-ID: X-spambait: aardvark@kernelnewbies.org X-spammeplease: aardvark@nl.linux.org MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Tue, 17 Apr 2001, Matt Dillon wrote: > :You need to settle dude, pre-emption isn't a goal, it's mearly a > :_possible_ side effect. > : > :We're not aiming for pre-emption, we're aiming for more concurrancy. > > A goal of having more concurrency is laudable, but I think you are > ignoring the costs of doing task switches verses the likely spin time > for a mutex. The whole point of using fine-grained Mutexes is to not > have significant performance-effecting collisions in the first place, > so why bother to try to task switch if you wind up spining in one? Exactly. It makes absolutely no sense to optimise mutexes for the case of having contention. If you have contention, you need to fix the contention, not introduce all kinds of singing-dancing cool things you can do when contention happens. Rik -- Virtual memory is like a game you can't win; However, without VM there's truly nothing to lose... http://www.surriel.com/ http://www.conectiva.com/ http://distro.conectiva.com.br/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message