Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932186AbbFDP6y (ORCPT ); Thu, 4 Jun 2015 11:58:54 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:57145 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932125AbbFDP6x (ORCPT ); Thu, 4 Jun 2015 11:58:53 -0400 X-Originating-IP: 50.43.43.179 Date: Thu, 4 Jun 2015 08:58:13 -0700 From: Josh Triplett To: Denys Vlasenko Cc: Ingo Molnar , Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] x86/asm/entry/32: Remove unnecessary optimization in stub32_clone Message-ID: <20150604155813.GA7829@x> References: <1433339930-20880-1-git-send-email-dvlasenk@redhat.com> <1433339930-20880-2-git-send-email-dvlasenk@redhat.com> <20150603163856.GA1744@x> <55702363.7090108@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55702363.7090108@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2137 Lines: 50 On Thu, Jun 04, 2015 at 12:07:31PM +0200, Denys Vlasenko wrote: > On 06/03/2015 06:38 PM, Josh Triplett wrote: > > On Wed, Jun 03, 2015 at 03:58:50PM +0200, Denys Vlasenko wrote: > >> Really swap arguments #4 and #5 in stub32_clone instead of "optimizing" > >> it into a move. > >> > >> Yes, tls_val is currently unused. Yes, on some CPUs XCHG is a little bit > >> more expensive than MOV. But a cycle or two on an expensive syscall like > >> clone() is way below noise floor, and this optimization is simply not worth > >> the obfuscation of logic. > > [...] > >> This is a resend. > >> > >> There was a patch by Josh Triplett > >> "x86: Opt into HAVE_COPY_THREAD_TLS, for both 32-bit and 64-bit" > >> sent on May 11, > >> which does the same thing as part of a bigger cleanup. > >> He was supportive of this patch because of comments. > >> He will simply have to drop one hunk from his patch. > > > > Strictly speaking, nothing needs this until clone starts paying > > attention to its tls argument, which only happens in my cleanup series > > that includes this change. So what's the purpose of driving this patch > > separately? > > You wanted my comments in this patch to go in: > > On 04/22/2015 07:10 PM, Josh Triplett wrote: > > I do think my two-patch HAVE_COPY_THREAD_TLS series should go in fixing > > this, but I'd like to see the final version of Denys' comment added on > > top of it (with an update to the type and name of the tls argument to > > match the changes to sys_clone). > > If your patch will go in first, I'll send a patch adding only the comment. > > Since for now your patch did not make it yet, I'm submitting > a patch which adds both a comment and the insn change. Ah, I see. My two-patch series is currently sitting in -mm; would you consider providing a version of the patch that adds the comment for Andrew to apply on top of those? - Josh Triplett -- 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/