Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964807AbXBNWKi (ORCPT ); Wed, 14 Feb 2007 17:10:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964804AbXBNWKi (ORCPT ); Wed, 14 Feb 2007 17:10:38 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:36186 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964805AbXBNWKh (ORCPT ); Wed, 14 Feb 2007 17:10:37 -0500 Subject: Re: [patch] x86: split FPU state from task state From: Arjan van de Ven To: Benjamin LaHaise Cc: Ingo Molnar , Davide Libenzi , Russell King , Linux Kernel Mailing List , Linus Torvalds , Christoph Hellwig , Andrew Morton , Alan Cox , Ulrich Drepper , Zach Brown , Evgeniy Polyakov , "David S. Miller" , Suparna Bhattacharya , Thomas Gleixner In-Reply-To: <20070214220443.GN32271@kvack.org> References: <20070214103655.GB4241@flint.arm.linux.org.uk> <20070214105039.GC6801@elte.hu> <20070214110419.GC4241@flint.arm.linux.org.uk> <20070214180344.GI32271@kvack.org> <20070214200347.GK32271@kvack.org> <20070214203438.GL32271@kvack.org> <20070214214944.GA1082@elte.hu> <20070214220443.GN32271@kvack.org> Content-Type: text/plain Organization: Intel International BV Date: Wed, 14 Feb 2007 23:10:17 +0100 Message-Id: <1171491017.12771.483.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2.1 (2.8.2.1-3.fc6) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1393 Lines: 33 On Wed, 2007-02-14 at 17:04 -0500, Benjamin LaHaise wrote: > On Wed, Feb 14, 2007 at 10:49:44PM +0100, Ingo Molnar wrote: > > this can very much be done, with a straightforward extension of how we > > handle FPU state. That makes sense independently of syslets/async as > > well, so find below the standalone patch from Arjan. It's in my current > > syslet queue and works great. > > That patch adds a bunch of memory dereferences not really; you missed that most of the ->'s are actually just going to members of the union and aren't actually extra dereference. > and another allocation > to the thread creation code path -- a tax that all users must pay. so the next step, as mentioned in the changelog, to allocate only on the first FPU fault, so that it becomes a GAIN for everyone, since only threads that use FPU will use the memory. The second gain (although only on old cpus) is that you only need to allocate enough memory for your cpu, rather than 512 always. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - 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/