From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754302Ab3JJHyu (ORCPT ); Thu, 10 Oct 2013 03:54:50 -0400 Received: from mail-ee0-f43.google.com ([74.125.83.43]:40996 "EHLO mail-ee0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996Ab3JJHys (ORCPT ); Thu, 10 Oct 2013 03:54:48 -0400 Date: Thu, 10 Oct 2013 09:54:44 +0200 From: Ingo Molnar To: Tim Chen Cc: Ingo Molnar , Andrew Morton , Linus Torvalds , Andrea Arcangeli , Alex Shi , Andi Kleen , Michel Lespinasse , Davidlohr Bueso , Matthew R Wilcox , Dave Hansen , Peter Zijlstra , Rik van Riel , Peter Hurley , "Paul E.McKenney" , Jason Low , Waiman Long , linux-kernel@vger.kernel.org, linux-mm Subject: Re: [PATCH v8 0/9] rwsem performance optimizations Message-ID: <20131010075444.GD17990@gmail.com> References: <1380753493.11046.82.camel@schen9-DESK> <20131003073212.GC5775@gmail.com> <1381186674.11046.105.camel@schen9-DESK> <20131009061551.GD7664@gmail.com> <1381336441.11046.128.camel@schen9-DESK> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1381336441.11046.128.camel@schen9-DESK> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Tim Chen wrote: > The throughput of pure mmap with mutex is below vs pure mmap is below: > > % change in performance of the mmap with pthread-mutex vs pure mmap > #threads vanilla all rwsem without optspin > patches > 1 3.0% -1.0% -1.7% > 5 7.2% -26.8% 5.5% > 10 5.2% -10.6% 22.1% > 20 6.8% 16.4% 12.5% > 40 -0.2% 32.7% 0.0% > > So with mutex, the vanilla kernel and the one without optspin both run > faster. This is consistent with what Peter reported. With optspin, the > picture is more mixed, with lower throughput at low to moderate number > of threads and higher throughput with high number of threads. So, going back to your orignal table: > % change in performance of the mmap with pthread-mutex vs pure mmap > #threads vanilla all without optspin > 1 3.0% -1.0% -1.7% > 5 7.2% -26.8% 5.5% > 10 5.2% -10.6% 22.1% > 20 6.8% 16.4% 12.5% > 40 -0.2% 32.7% 0.0% > > In general, vanilla and no-optspin case perform better with > pthread-mutex. For the case with optspin, mmap with pthread-mutex is > worse at low to moderate contention and better at high contention. it appears that 'without optspin' appears to be a pretty good choice - if it wasn't for that '1 thread' number, which, if I correctly assume is the uncontended case, is one of the most common usecases ... How can the single-threaded case get slower? None of the patches should really cause noticeable overhead in the non-contended case. That looks weird. It would also be nice to see the 2, 3, 4 thread numbers - those are the most common contention scenarios in practice - where do we see the first improvement in performance? Also, it would be nice to include a noise/sttdev figure, it's really hard to tell whether -1.7% is statistically significant. Thanks, Ingo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f179.google.com (mail-pd0-f179.google.com [209.85.192.179]) by kanga.kvack.org (Postfix) with ESMTP id 0E14C6B0031 for ; Thu, 10 Oct 2013 03:54:50 -0400 (EDT) Received: by mail-pd0-f179.google.com with SMTP id v10so2214433pde.24 for ; Thu, 10 Oct 2013 00:54:50 -0700 (PDT) Received: by mail-ee0-f54.google.com with SMTP id e53so947575eek.13 for ; Thu, 10 Oct 2013 00:54:47 -0700 (PDT) Date: Thu, 10 Oct 2013 09:54:44 +0200 From: Ingo Molnar Subject: Re: [PATCH v8 0/9] rwsem performance optimizations Message-ID: <20131010075444.GD17990@gmail.com> References: <1380753493.11046.82.camel@schen9-DESK> <20131003073212.GC5775@gmail.com> <1381186674.11046.105.camel@schen9-DESK> <20131009061551.GD7664@gmail.com> <1381336441.11046.128.camel@schen9-DESK> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1381336441.11046.128.camel@schen9-DESK> Sender: owner-linux-mm@kvack.org List-ID: To: Tim Chen Cc: Ingo Molnar , Andrew Morton , Linus Torvalds , Andrea Arcangeli , Alex Shi , Andi Kleen , Michel Lespinasse , Davidlohr Bueso , Matthew R Wilcox , Dave Hansen , Peter Zijlstra , Rik van Riel , Peter Hurley , "Paul E.McKenney" , Jason Low , Waiman Long , linux-kernel@vger.kernel.org, linux-mm * Tim Chen wrote: > The throughput of pure mmap with mutex is below vs pure mmap is below: > > % change in performance of the mmap with pthread-mutex vs pure mmap > #threads vanilla all rwsem without optspin > patches > 1 3.0% -1.0% -1.7% > 5 7.2% -26.8% 5.5% > 10 5.2% -10.6% 22.1% > 20 6.8% 16.4% 12.5% > 40 -0.2% 32.7% 0.0% > > So with mutex, the vanilla kernel and the one without optspin both run > faster. This is consistent with what Peter reported. With optspin, the > picture is more mixed, with lower throughput at low to moderate number > of threads and higher throughput with high number of threads. So, going back to your orignal table: > % change in performance of the mmap with pthread-mutex vs pure mmap > #threads vanilla all without optspin > 1 3.0% -1.0% -1.7% > 5 7.2% -26.8% 5.5% > 10 5.2% -10.6% 22.1% > 20 6.8% 16.4% 12.5% > 40 -0.2% 32.7% 0.0% > > In general, vanilla and no-optspin case perform better with > pthread-mutex. For the case with optspin, mmap with pthread-mutex is > worse at low to moderate contention and better at high contention. it appears that 'without optspin' appears to be a pretty good choice - if it wasn't for that '1 thread' number, which, if I correctly assume is the uncontended case, is one of the most common usecases ... How can the single-threaded case get slower? None of the patches should really cause noticeable overhead in the non-contended case. That looks weird. It would also be nice to see the 2, 3, 4 thread numbers - those are the most common contention scenarios in practice - where do we see the first improvement in performance? Also, it would be nice to include a noise/sttdev figure, it's really hard to tell whether -1.7% is statistically significant. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org