Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932093Ab1C3NME (ORCPT ); Wed, 30 Mar 2011 09:12:04 -0400 Received: from tx2ehsobe001.messaging.microsoft.com ([65.55.88.11]:28306 "EHLO TX2EHSOBE001.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754409Ab1C3NMD (ORCPT ); Wed, 30 Mar 2011 09:12:03 -0400 X-SpamScore: -27 X-BigFish: VPS-27(zzbb2dK1418M1432N98dN9371Pzz1202hzzz32i637h668h61h) X-Spam-TCS-SCL: 0:0 X-Forefront-Antispam-Report: KIP:(null);UIP:(null);IPVD:NLI;H:ausb3twp01.amd.com;RD:none;EFVD:NLI X-WSS-ID: 0LIVGNT-01-2VK-02 X-M-MSG: Date: Wed, 30 Mar 2011 15:11:46 +0200 From: Hans Rosenfeld To: "H. Peter Anvin" CC: Brian Gerst , "tglx@linutronix.de" , "mingo@elte.hu" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "suresh.b.siddha@intel.com" , "eranian@google.com" , "Richter, Robert" , "Herrmann3, Andreas" Subject: Re: [RFC v2 8/8] x86, xsave: remove lazy allocation of xstate area Message-ID: <20110330131146.GO13@escobedo.osrc.amd.com> References: <1299698102-972771-9-git-send-email-hans.rosenfeld@amd.com> <1300894067-604408-9-git-send-email-hans.rosenfeld@amd.com> <20110329141712.GM13@escobedo.osrc.amd.com> <4D91FA76.1010908@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <4D91FA76.1010908@zytor.com> Organization: Advanced Micro Devices GmbH, Einsteinring 24, 85609 Dornach b. Muenchen; Geschaeftsfuehrer: Andrew Bowd, Alberto Bozzo; Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen; Registergericht Muenchen, HRB Nr. 43632 User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginatorOrg: amd.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 39 On Tue, Mar 29, 2011 at 11:27:50AM -0400, H. Peter Anvin wrote: > On 03/29/2011 07:17 AM, Hans Rosenfeld wrote: > >> > >> I'm not sure I like this. I did a quick test on 64-bit, and found > >> that while most if not all user processes allocated the fpu save area > >> (probably because of glibc blindly initializing the fpu), kernel > >> threads did not. This patch would force kernel threads to allocate > >> memory they would never use. > > > > Yes, up to a few kilobytes would be wasted by kernel threads. The > > related code gets much simpler. I think that is a good thing. > > > > This is silly. It shouldn't be very hard to allocate this for user > threads while avoiding the allocation for kernel threads. The only > excuse for allocating it for user threads is if it becomes part of the > kernel stack allocation. The allocation itself is not what I'm concerned about. I'm more worried about the code that always has to check whether a thread has a xstate area allocated or not. But I will try and find out to get this done the way you suggested. Meanwhile, could you please review the other patches? They are much more important to me. Hans -- %SYSTEM-F-ANARCHISM, The operating system has been overthrown -- 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/