From owner-svn-src-head@FreeBSD.ORG Tue Dec 16 19:06:29 2008 Return-Path: Delivered-To: svn-src-head@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E4EE61065693; Tue, 16 Dec 2008 19:06:29 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (bsdimp.com [199.45.160.85]) by mx1.freebsd.org (Postfix) with ESMTP id A34488FC55; Tue, 16 Dec 2008 19:06:29 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from localhost (localhost [127.0.0.1]) by harmony.bsdimp.com (8.14.2/8.14.1) with ESMTP id mBGJ48KA063565; Tue, 16 Dec 2008 12:04:08 -0700 (MST) (envelope-from imp@bsdimp.com) Date: Tue, 16 Dec 2008 12:04:12 -0700 (MST) Message-Id: <20081216.120412.1346820326.imp@bsdimp.com> To: scottl@samsco.org From: "M. Warner Losh" In-Reply-To: <4947F363.4010909@samsco.org> References: <4947D474.9040802@samsco.org> <20081216.101038.1172765453.imp@bsdimp.com> <4947F363.4010909@samsco.org> X-Mailer: Mew version 5.2 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: svn-src-head@FreeBSD.org, mav@FreeBSD.org, src-committers@FreeBSD.org, svn-src-all@FreeBSD.org Subject: Re: svn commit: r186182 - head/sys/dev/ata X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Dec 2008 19:06:30 -0000 In message: <4947F363.4010909@samsco.org> Scott Long writes: : M. Warner Losh wrote: : > In message: <4947D474.9040802@samsco.org> : > Scott Long writes: : > : Alexander Motin wrote: : > : > Author: mav : > : > Date: Tue Dec 16 16:04:40 2008 : > : > New Revision: 186182 : > : > URL: http://svn.freebsd.org/changeset/base/186182 : > : > : > : > Log: : > : > Call ata_legacy() only once on attach and save it's result. Scanning PCI : > : > configuration registers (which are not going to change) on every interrupt : > : > looks expensive, especially when interrupt is shared. Profiling shows me 3% : > : > of time spent by atapci0 on pure network load due to IRQ sharing with em0. : > : > : > : : > : Nice change. PCI Config registers are exceptionally slow to access on : > : most systems. : > : > And we've been recommending to people for years that they avoid config : > space access in interrupt handlers. Maybe it is time for something : > that checks and prints a warning? : > : : With the move to memory-mapped pci config registers, there was an : intention to allow low-end devices to put their registers into config : space. I think I recall some legacy ultra-low end devices that also : put a few required registers into config space. So while it's not ideal : to access it from an interrupt handler, I can't think of why it should : be expressly forbidden. True. I wasn't planning on banning it, just warning about it so we could be purposeful in our use of it. Likely unworkable though... Warner