From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758291AbYHKX54 (ORCPT ); Mon, 11 Aug 2008 19:57:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754034AbYHKX5r (ORCPT ); Mon, 11 Aug 2008 19:57:47 -0400 Received: from gw.goop.org ([64.81.55.164]:55878 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753691AbYHKX5q (ORCPT ); Mon, 11 Aug 2008 19:57:46 -0400 Message-ID: <48A0D1E6.5030609@goop.org> Date: Mon, 11 Aug 2008 16:57:26 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Andi Kleen CC: Ingo Molnar , LKML , x86@kernel.org, Nick Piggin , Jens Axboe Subject: Re: [PATCH 0 of 8] x86/smp function calls: convert x86 tlb flushes to use function calls References: <87k5eu6d4f.fsf@basil.nowhere.org> <48991B84.2080704@goop.org> <20080806033736.GB24801@one.firstfloor.org> In-Reply-To: <20080806033736.GB24801@one.firstfloor.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen wrote: > Micro benchmark. Just stick RDTSC around the calls and trigger > a few remote flushes by e.g. doing mmap/munmap on a multithreaded program > running on different CPUs. > On a HT 3GHz Xeon, I see a ~35% increase in time (1830ns -> 2500ns), averaged over 1000,000 interrupts. Because it's only 2 cpu, it ends up always using the smp_call_function_single path (but via the smp_call_function_mask path). I need to try getting a more-cpu machine running native to do a proper test, esp to see if putting kmalloc on that path is very expensive or not. (Is it worth using a kmem_cache?) J