Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753786AbYKQTng (ORCPT ); Mon, 17 Nov 2008 14:43:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751982AbYKQTn2 (ORCPT ); Mon, 17 Nov 2008 14:43:28 -0500 Received: from out1.smtp.messagingengine.com ([66.111.4.25]:44733 "EHLO out1.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751760AbYKQTn1 (ORCPT ); Mon, 17 Nov 2008 14:43:27 -0500 Message-Id: <1226951006.21581.1285268501@webmail.messagingengine.com> X-Sasl-Enc: miKpvuoRtIb839Pju62XFX/0CquxEuYFsn0UOrqlAdiL 1226951006 From: "Alexander van Heukelum" To: "Cyrill Gorcunov" , "Andi Kleen" Cc: "Ingo Molnar" , "LKML" , "Alexander van Heukelum" , "Glauber Costa" Content-Disposition: inline Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 X-Mailer: MessagingEngine.com Webmail Interface References: <1226845741-12470-1-git-send-email-heukelum@fastmail.fm> <1226845741-12470-2-git-send-email-heukelum@fastmail.fm> <20081117125317.GK6703@one.firstfloor.org> <1226936257.32609.1285214311@webmail.messagingengine.com> <20081117182340.GN6703@one.firstfloor.org> <20081117192216.GA9944@localhost> Subject: Re: [RFC] x86: save_args out of line In-Reply-To: <20081117192216.GA9944@localhost> Date: Mon, 17 Nov 2008 20:43:26 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 66 On Mon, 17 Nov 2008 22:22:16 +0300, "Cyrill Gorcunov" said: > [Andi Kleen - Mon, Nov 17, 2008 at 07:23:40PM +0100] > ... > | > | Ok. Hopefully it's worth the effort. The branch misprediction bubble > | should not be too bad, perhaps it'll make up for the other cycles > | you're adding. But even if it doesn't decreasing cache line foot print > is > | always a good thing. > ... > > May I turn in? :) Sure! > Original .macro interrupt func has > > testl $3, CS(%rdi) > je 1f > SWAPGS > 1: incl %gs:pda_irqcount inc changes flags... > jne 2f > pop %rax > mov %gs:pda_irqstackptr,%rsp > push %rax > 2: TRACE_IRQS_OFF > > Wouldn't we help the branch predictor a bit by > > testl $3, CS(%rdi) > je 1f > SWAPGS > jne 2f ... so this is not the same. > 1: pop %rax > mov %gs:pda_irqstackptr,%rsp > push %rax > 2: incl %gs:pda_irqcount > TRACE_IRQS_OFF > > I hope I didn't miss anything but maybe it's just a churning > or plain wrong. Don't shoot me :) I'm sure it helps the branch predictor, though ;). Alexander > - Cyrill - -- Alexander van Heukelum heukelum@fastmail.fm -- http://www.fastmail.fm - A fast, anti-spam email service. -- 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/