From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63E11C282DA for ; Wed, 17 Apr 2019 20:30:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20139206BA for ; Wed, 17 Apr 2019 20:30:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732742AbfDQUah convert rfc822-to-8bit (ORCPT ); Wed, 17 Apr 2019 16:30:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48710 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727147AbfDQUah (ORCPT ); Wed, 17 Apr 2019 16:30:37 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 527053005FF9; Wed, 17 Apr 2019 20:30:36 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-47.bos.redhat.com [10.18.17.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0208A60C64; Wed, 17 Apr 2019 20:30:34 +0000 (UTC) Subject: Re: [PATCH-tip 0/2] locking/rwsem: Rwsem rearchitecture part 2 follow-up patches To: Ingo Molnar Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner , linux-kernel@vger.kernel.org, x86@kernel.org, Davidlohr Bueso , Linus Torvalds , Tim Chen , huang ying References: <20190415205829.32707-1-longman@redhat.com> <20190416131047.GW11158@hirez.programming.kicks-ass.net> <4747d10b-e9a4-f453-ab4e-13fc984a4067@redhat.com> <20190416141747.GN4038@hirez.programming.kicks-ass.net> <18af71ce-1ef3-c6cd-4088-3b2a9bf0016e@redhat.com> <20190416173700.GQ4038@hirez.programming.kicks-ass.net> <2873c42c-f2a6-64e9-bf0f-9c86536984b7@redhat.com> <20190417055745.GA95755@gmail.com> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; prefer-encrypt=mutual; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190417055745.GA95755@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Wed, 17 Apr 2019 20:30:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/17/2019 01:57 AM, Ingo Molnar wrote: > * Waiman Long wrote: > >> On 04/16/2019 01:37 PM, Peter Zijlstra wrote: >>> On Tue, Apr 16, 2019 at 01:03:10PM -0400, Waiman Long wrote: >>>> On 04/16/2019 10:17 AM, Peter Zijlstra wrote: >>>>> On Tue, Apr 16, 2019 at 09:18:50AM -0400, Waiman Long wrote: >>>>>> On 04/16/2019 09:10 AM, Peter Zijlstra wrote: >>>>>>> On Mon, Apr 15, 2019 at 04:58:27PM -0400, Waiman Long wrote: >>>>>>>> This series contain 2 follow-up patches to alleviate the performance >>>>>>>> regression found in the page_fault1 test of the will-it-scale benchmark. >>>>>>>> This does not recover all the lost performance, but reclaim a sizeable >>>>>>>> portion of it. >>>>>>>> >>>>>>>> The regression was found on an Intel system. I have run the test on >>>>>>>> an AMD system. The regression wasn't seen there. There are only minor >>>>>>>> variations in performance. Perhaps the page fault path is quite different >>>>>>>> between Intel and AMD systems. >>>>>>> Can you please just fold this back into the appropriate patches? Trying >>>>>>> to review all the back and forth is painful. >>>>>> I will send out an update part 2 patch with patch 1 of this series >>>>>> merged into the writer spinning on reader patch. Patch 2 of this series >>>>>> will be a standalone one. >>>>> Hmm, in that case I can fold it back too. So hold off on sending it. >>>>> >>>>> I thought #2 was a fixup for an earlier patch as well. >>>> #2 is a performance fix. >>> Of this patch? >>> >>> 206038 N T Apr 13 Waiman Long (7.5K) ├─>[PATCH v4 11/16] locking/rwsem: Enable readers spinning on writer >>> >>> Fixes should have a Fixes: tag. And if the patch it fixes isn't a commit >>> yet, the patch should be refreshed to not need a fix. >> The original patch isn't wrong. This patch just introduce another idea >> to make it better. That is why I would still like to separate it as a >> distinct patch. > Yeah, I think it's better to have it in two separate patches. Basically > patch #1 has a downside for certain workloads, which the heuristics in > patch #2 improve. That's the only connection between the two patches. > > If we find some other worst-case workload then the split of the commits > would allow more finegrained examination of the effects of these > performance tunings. > > Thanks, > > Ingo As the part2 patches are still being actively modified, it doesn't look like it will make the next merge window. I am fine with postponing it to 5.3. However, I would like to request the merging of just patch 1 of the part 2 patchset. It fixes a locking selftest problem that was introduced in the part 1 patches. Thanks, Longman