From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754101AbYHSJcA (ORCPT ); Tue, 19 Aug 2008 05:32:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752040AbYHSJbw (ORCPT ); Tue, 19 Aug 2008 05:31:52 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:53738 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751188AbYHSJbv (ORCPT ); Tue, 19 Aug 2008 05:31:51 -0400 Date: Tue, 19 Aug 2008 11:31:30 +0200 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: LKML , x86@kernel.org, Andi Kleen , Nick Piggin , Jens Axboe Subject: Re: [PATCH 0 of 9] x86/smp function calls: convert x86 tlb flushes to use function calls [POST 2] Message-ID: <20080819093130.GF28713@elte.hu> References: <20080819004531.GI9914@elte.hu> <48AA5C19.3010204@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48AA5C19.3010204@goop.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jeremy Fitzhardinge wrote: > Ingo Molnar wrote: > > nice stuff! > > > > I suspect the extra cost might be worth it for two reasons: 1) we could > > optimize the cross-call implementation further > > Unfortunately, I think the kmalloc fix for the RCU issue is going to > hurt quite a lot. yeah :-( Nick, is there any way to get rid of that kmalloc() in the async function call case? The whole premise of the smp_function_call() rewrite was that it's faster - and now it's measurably slower. At least we could/should perhaps standardize/generalize all the 'specific' IPI handlers into the smp_function_call() framework: if function address equals to a pre-cooked IPI entry point we could call that function without a kmalloc. As these are all hardwired, __builtin_is_constant_p() could come to the help as well. Hm? Ingo