From owner-cvs-all Fri Nov 6 12:08:23 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id MAA23790 for cvs-all-outgoing; Fri, 6 Nov 1998 12:08:23 -0800 (PST) (envelope-from owner-cvs-all@FreeBSD.ORG) Received: from dingo.cdrom.com (dingo.cdrom.com [204.216.28.145]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id MAA23785; Fri, 6 Nov 1998 12:08:20 -0800 (PST) (envelope-from mike@dingo.cdrom.com) Received: from dingo.cdrom.com (localhost.cdrom.com [127.0.0.1]) by dingo.cdrom.com (8.9.1/8.8.8) with ESMTP id MAA00469; Fri, 6 Nov 1998 12:06:35 -0800 (PST) (envelope-from mike@dingo.cdrom.com) Message-Id: <199811062006.MAA00469@dingo.cdrom.com> X-Mailer: exmh version 2.0.2 2/24/98 To: Matthew Dillon cc: David Greenman , cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: sendfile.2 (was Re: cvs commit: ...) In-reply-to: Your message of "Fri, 06 Nov 1998 10:05:10 PST." <199811061805.KAA00657@apollo.backplane.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 06 Nov 1998 12:06:35 -0800 From: Mike Smith Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk > > The interesting thing about this is that the number of context switches > does not seem to be the deciding factor... otherwise I would have expected > the blocking write() case to have a more significant spread. Instead, > it appears to be the actual switch to and from user mode that is causing > the greatest overhead. The block-write() case does not return to usermode > while the non-blocking sendfile() case does. Either that, or select()ing > on a single descriptor is more expensive then I thought it was. That's about consistent with expectations; context switch from one process context to another is about as fast as it can be. Crossing the user:kernel protection boundary is not so easy - one of the major shortcomings of the i386 architecture it seems. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message