Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262030AbVANRJ2 (ORCPT ); Fri, 14 Jan 2005 12:09:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262029AbVANRJ2 (ORCPT ); Fri, 14 Jan 2005 12:09:28 -0500 Received: from omx3-ext.sgi.com ([192.48.171.20]:44215 "EHLO omx3.sgi.com") by vger.kernel.org with ESMTP id S262028AbVANRJT (ORCPT ); Fri, 14 Jan 2005 12:09:19 -0500 Date: Fri, 14 Jan 2005 09:08:54 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Andi Kleen cc: Nick Piggin , Andrew Morton , torvalds@osdl.org, hugh@veritas.com, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org Subject: Re: page table lock patch V15 [0/7]: overview In-Reply-To: <20050114170140.GB4634@muc.de> Message-ID: References: <41E5B7AD.40304@yahoo.com.au> <41E5BC60.3090309@yahoo.com.au> <20050113031807.GA97340@muc.de> <20050113180205.GA17600@muc.de> <20050114043944.GB41559@muc.de> <20050114170140.GB4634@muc.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1132 Lines: 22 On Fri, 14 Jan 2005, Andi Kleen wrote: > > Looked at arch/i386/lib/mmx.c. It avoids the mmx ops in an interrupt > > context but the rest of the prep for mmx only saves the fpu state if its > > in use. So that code would only be used rarely. The mmx 64 bit > > instructions seem to be quite fast according to the manual. Double the > > cycles than the 32 bit instructions on Pentium M (somewhat higher on Pentium 4). > > With all the other overhead (disabling exceptions, saving register etc.) > will be likely slower. Also you would need fallback paths for CPUs > without MMX but with PAE (like Ppro). You can benchmark > it if you want, but I wouldn't be very optimistic. So the PentiumPro is a cpu with atomic 64 bit operations in a cmpxchg but no instruction to do an atomic 64 bit store or load although the architecture conceptually supports 64bit atomic stores and loads? Wild. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/