Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030304AbVLVVj1 (ORCPT ); Thu, 22 Dec 2005 16:39:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030306AbVLVVj0 (ORCPT ); Thu, 22 Dec 2005 16:39:26 -0500 Received: from mf00.sitadelle.com ([212.94.174.67]:11647 "EHLO smtp.cegetel.net") by vger.kernel.org with ESMTP id S1030304AbVLVVj0 (ORCPT ); Thu, 22 Dec 2005 16:39:26 -0500 Message-ID: <43AB1D01.5000703@cosmosbay.com> Date: Thu, 22 Dec 2005 22:39:13 +0100 From: Eric Dumazet User-Agent: Thunderbird 1.5 (Windows/20051201) MIME-Version: 1.0 To: Ingo Molnar Cc: Steven Rostedt , Pekka Enberg , Christoph Lameter , Alok N Kataria , Shobhit Dayal , Shai Fultheim , Matt Mackall , Andrew Morton , john stultz , Gunter Ohrner , linux-kernel@vger.kernel.org Subject: Re: [PATCH RT 00/02] SLOB optimizations References: <1135093460.13138.302.camel@localhost.localdomain> <20051220181921.GF3356@waste.org> <1135106124.13138.339.camel@localhost.localdomain> <84144f020512201215j5767aab2nc0a4115c4501e066@mail.gmail.com> <1135114971.13138.396.camel@localhost.localdomain> <20051221065619.GC766@elte.hu> <43A90225.4060007@cosmosbay.com> <20051221074346.GA2398@elte.hu> <43A90C07.4000003@cosmosbay.com> <20051222211132.GA21742@elte.hu> In-Reply-To: <20051222211132.GA21742@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1472 Lines: 42 Ingo Molnar a ?crit : > * Eric Dumazet wrote: > >>> in any case, on sane platforms (i386, x86_64) an irq-disable is >>> well-optimized in hardware, and is just as fast as a preempt_disable(). >> I'm afraid its not the case on current hardware. >> >> The irq enable/disable pair count for more than 50% the cpu time spent >> in kmem_cache_alloc()/kmem_cache_free()/kfree() > > because you are not using NMI based profiling? > >> oprofile results on a dual Opteron 246 : >> >> You can see the high profile numbers right after cli and popf(sti) >> instructions, popf being VERY expensive. > > that's just the profiling interrupt hitting them. You should not analyze > irq-safe code with a non-NMI profiling interrupt. > I'm using oprofile on Opteron, and AFAIK it's NMI based. # grep NMI /proc/interrupts ; sleep 1 ; grep NMI /proc/interrupts NMI: 391352095 2867983903 NMI: 391359678 2867998498 thats 7583 and 14595 NMI / second on cpu0 and cpu1 respectivly in this sample. > CLI/STI is extremely fast. (In fact in the -rt tree i'm using them > within mutexes instead of preempt_enable()/preempt_disable(), because > they are faster and generate less register side-effect.) > > Ingo > > - 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/