From owner-freebsd-smp Sat Dec 14 10:39:26 1996 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.4/8.8.4) id KAA26358 for smp-outgoing; Sat, 14 Dec 1996 10:39:26 -0800 (PST) Received: from dyson.iquest.net (dyson.iquest.net [198.70.144.127]) by freefall.freebsd.org (8.8.4/8.8.4) with ESMTP id KAA26347 for ; Sat, 14 Dec 1996 10:39:23 -0800 (PST) Received: (from root@localhost) by dyson.iquest.net (8.8.2/8.6.9) id NAA00208; Sat, 14 Dec 1996 13:38:47 -0500 (EST) From: "John S. Dyson" Message-Id: <199612141838.NAA00208@dyson.iquest.net> Subject: Re: some questions concerning TLB shootdowns in FreeBSD To: peter@spinner.dialix.com (Peter Wemm) Date: Sat, 14 Dec 1996 13:38:47 -0500 (EST) Cc: smp@freebsd.org, haertel@ichips.intel.com In-Reply-To: <199612141503.XAA17454@spinner.DIALix.COM> from "Peter Wemm" at Dec 14, 96 11:03:51 pm Reply-To: dyson@freebsd.org X-Mailer: ELM [version 2.4 PL24 ME8] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-smp@freebsd.org X-Loop: FreeBSD.org Precedence: bulk > > I'm still digesting it, I am almost worried that we might (shudder!) > be forced into doing an IPI to stop all the cpu's *before* the > current cpu changes the page tables, then letting them do the tlb > flush and letting them proceed. If this actually is a real problem > this means a much bigger code impact. > The way that I see it, is that the current pmap code is highly optimized for single processor operation. If I was you, I would try to just try to get something working correctly algorithmically -- almost ignoring performance issues. Of course, when performance is easy -- go for that also. Alot of things like single page invalidates inside of loops appear that they could be evil for multi-processor applications (imagine an inter- processor interrupt for every loop!?!?.) I think that you (we or us), will have to look at the performance for the SMP direction, and it might even entail large differences in pmap eventually. Hopefully, we will all be able to isolate the differences for the maintenance of sanity :-). John