Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751600AbdLUIRL (ORCPT ); Thu, 21 Dec 2017 03:17:11 -0500 Received: from mx2.suse.de ([195.135.220.15]:45199 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751084AbdLUIRJ (ORCPT ); Thu, 21 Dec 2017 03:17:09 -0500 Date: Thu, 21 Dec 2017 09:17:06 +0100 From: Michal Hocko To: kemi Cc: Greg Kroah-Hartman , Andrew Morton , Vlastimil Babka , Mel Gorman , Johannes Weiner , Christopher Lameter , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Pavel Tatashin , David Rientjes , Sebastian Andrzej Siewior , Dave , Andi Kleen , Tim Chen , Jesper Dangaard Brouer , Ying Huang , Aaron Lu , Aubrey Li , Linux MM , Linux Kernel Subject: Re: [PATCH v2 3/5] mm: enlarge NUMA counters threshold size Message-ID: <20171221081706.GA4831@dhcp22.suse.cz> References: <1513665566-4465-1-git-send-email-kemi.wang@intel.com> <1513665566-4465-4-git-send-email-kemi.wang@intel.com> <20171219124045.GO2787@dhcp22.suse.cz> <439918f7-e8a3-c007-496c-99535cbc4582@intel.com> <20171220101229.GJ4831@dhcp22.suse.cz> <268b1b6e-ff7a-8f1a-f97c-f94e14591975@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <268b1b6e-ff7a-8f1a-f97c-f94e14591975@intel.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2281 Lines: 55 On Thu 21-12-17 16:06:50, kemi wrote: > > > On 2017年12月20日 18:12, Michal Hocko wrote: > > On Wed 20-12-17 13:52:14, kemi wrote: > >> > >> > >> On 2017年12月19日 20:40, Michal Hocko wrote: > >>> On Tue 19-12-17 14:39:24, Kemi Wang wrote: > >>>> We have seen significant overhead in cache bouncing caused by NUMA counters > >>>> update in multi-threaded page allocation. See 'commit 1d90ca897cb0 ("mm: > >>>> update NUMA counter threshold size")' for more details. > >>>> > >>>> This patch updates NUMA counters to a fixed size of (MAX_S16 - 2) and deals > >>>> with global counter update using different threshold size for node page > >>>> stats. > >>> > >>> Again, no numbers. > >> > >> Compare to vanilla kernel, I don't think it has performance improvement, so > >> I didn't post performance data here. > >> But, if you would like to see performance gain from enlarging threshold size > >> for NUMA stats (compare to the first patch), I will do that later. > > > > Please do. I would also like to hear _why_ all counters cannot simply > > behave same. In other words why we cannot simply increase > > stat_threshold? Maybe calculate_normal_threshold needs a better scaling > > for larger machines. > > > > I will add this performance data to changelog in V3 patch series. > > Test machine: 2-sockets skylake platform (112 CPUs, 62G RAM) > Benchmark: page_bench03 > Description: 112 threads do single page allocation/deallocation in parallel. > before after > (enlarge threshold size) > CPU cycles 722 379(-47.5%) Please describe the numbers some more. Is this an average? What is the std? Can you see any difference with a more generic workload? > Some thinking about that: > a) the overhead due to cache bouncing caused by NUMA counter update in fast path > severely increase with more and more CPUs cores What is an effect on a smaller system with fewer CPUs? > b) AFAIK, the typical usage scenario (similar at least)for which this optimization can > benefit is 10/40G NIC used in high-speed data center network of cloud service providers. I would expect those would disable the numa accounting altogether. -- Michal Hocko SUSE Labs