Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6;
Date:   Tue, 28 Nov 2023 09:45:47 +0800
From:   Oliver Sang <oliver.sang@intel.com>
To:     Yosry Ahmed <yosryahmed@google.com>
CC:     <oe-lkp@lists.linux.dev>, <lkp@intel.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Domenico Cerasuolo <cerasuolodomenico@gmail.com>,
        <cgroups@vger.kernel.org>, <linux-mm@kvack.org>,
        <ying.huang@intel.com>, <feng.tang@intel.com>,
        <fengwei.yin@intel.com>, Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Ivan Babrou <ivan@cloudflare.com>, Tejun Heo <tj@kernel.org>,
        Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        "Waiman Long" <longman@redhat.com>, <kernel-team@cloudflare.com>,
        Wei Xu <weixugc@google.com>, Greg Thelen <gthelen@google.com>,
        <linux-kernel@vger.kernel.org>, <oliver.sang@intel.com>
Subject: Re: [PATCH v3 3/5] mm: memcg: make stats flushing threshold per-memcg
Message-ID: <ZWVGS2rNgueGH8uU@xsang-OptiPlex-9020>
References: <20231116022411.2250072-4-yosryahmed@google.com>
 <202311221542.973f16ad-oliver.sang@intel.com>
 <CAJD7tkYnn6CxSJdo0QJ1hc6cFY_qWLuJ0=S6g_Pm=GBV+Ss-jw@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CAJD7tkYnn6CxSJdo0QJ1hc6cFY_qWLuJ0=S6g_Pm=GBV+Ss-jw@mail.gmail.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?WWp1bnlUMnFVSjN4cG9kbnpBZFF1aU5tWjJ4MWozck5YVGlLUWgwUk93SUth?=
 =?utf-8?B?dlRpa0UvZ1E0UXBiakJ3R21TVXp0TUNlK0lxOEYwWStnUC8xTDF1U1V3TmRo?=
 =?utf-8?B?N2VnTjdXV25sSEZNeTU1U0gvQ281YitnQWhWWE94SURJaDdZc3FpK3RQek15?=
 =?utf-8?B?YWg3MjJYSEU3QjlsS0VoMFR0bkVzUEdqTTlxOERienFCVWlGVGJrdHBwRVJu?=
 =?utf-8?B?aFBpbDAreGlrV3kvelNSYU9xenJiclYyR3hhRWRxckFxQVNVc1MyUWIxaFJj?=
 =?utf-8?B?NjNIdmJjUy9pYVYvdWxubVo1RmpNcXYyMHlFOTF2V1Fvd3dPZWFzVk0zV2FC?=
 =?utf-8?B?R2ZIYWFidVZHeDhuaUNqTDlyYmxjZDhraXVPclA2QmtBWUhiMVZjVnhkL01J?=
 =?utf-8?B?ZFg3WXQ1d2t3dmVoU1ZGWWZmVjVWQUVIZ1FNaExkRTFxZGE1UkZaNkoxZ0g5?=
 =?utf-8?B?MzlXQlVCeHQxblArRDhOZ3ViVC9vajhhK2JPdmZSNlRQd3h2QTA5VmY0ZG1O?=
 =?utf-8?B?emh6M0poQVVnRUhLdnFDTnNnVHQ5MkZhR09iK1VXWmFMcmIzb1orNW9UYTlX?=
 =?utf-8?B?WEI5K05wZEI4UHgyWmdYSUlvSGV0N3IzT001TWtWRlhXVldlN3BOTW9lOWZy?=
 =?utf-8?B?aE13WkxuczRHRkw3VUdSNFpEazcxdkFhbjE5M3lMQUEyT1ZkVC9BMWFySS9j?=
 =?utf-8?B?R3BCaVNxSnV2MVVRdWRJL2taOTN4TkJXNnBIT25pVnJMMnVZcG80VDgwcGVT?=
 =?utf-8?B?dmx5ZjVReWFnYmxCREY4WkdBdlJGeGw4U3FNMi9ac1VtZjZlb3BvQU95a1pz?=
 =?utf-8?B?ZFQvc2crVS9wLzNoK3UxQ0ZUenNxaUJoUHRqQXNaOWhORm5LMHlReXZVS045?=
 =?utf-8?B?dFF0RnBjWks2cUhsTTM3cE8vOUJTQmF1cWtCYXRtSC9tUVNSRFk5VnhwbVBU?=
 =?utf-8?B?MGRxZFR1Q1BDR01iOHR1NzdjM2JaRVVCNGJoalZ0ekFmSVdzVVlmTlRGeTFJ?=
 =?utf-8?B?WnJVWUIrOGUwMGNLZ0RaVW9Sd2pHWmsyMEZlTlZRa0Zick56UklPUVZ4L2hV?=
 =?utf-8?B?cDdYZXdpQXRkMmtiL2pwY0M0Z21wYm1qK3h4ZTdSYkl6eXc3bDNCTWVucUU0?=
 =?utf-8?B?ellZVWVrcHlmRlp5MWdTMXdrY0lEY0lEUWNyOXAvS0pTZTkvTVp5bllLR2FG?=
 =?utf-8?B?ajZQc1FJQ0VrcjhHV2N4SURkNFdCZGFFUUVmZG5RTW11OGxVaTRwNEorY1pJ?=
 =?utf-8?B?Uk5IUGdZM1FBOVRTS1ExUEpIVzJ6VDVJRDk4amZ6OE45ejNPTzRjakxPZXlY?=
 =?utf-8?B?SlR3cnBxamhYRExySjF4OUpYUnZaMGdpZFR0eEJKVDlwUHQ0YkorSFRtYjNk?=
 =?utf-8?B?eHRWWVJ4SlJzRVBvZkg1Zk5PeC8rOUJaSFJRczFDam9tMVdMRXhGcWpBNnZ3?=
 =?utf-8?B?NEM2T29CQjVOdVkxWVhGMWlqYkUwdURVWWVLNVVuZytQODZ4eGdtK0dwQVN6?=
 =?utf-8?B?U3dSM1gwblM2LzV0ajU1ck1nYnptMldISXNTSm94VUdFQ2MrSGdPZXh6NVNU?=
 =?utf-8?B?eTFZcWJYenptZ0lWbkR0ZjAzY29BeCtRU2tWbUw0N1Q0a1U2cG9nbWZqdjFH?=
 =?utf-8?B?ZmxEN1IxY3dOS2FRVW9sSUYrYUlWc2tEK0xwM0hSTUNFUEs5eTNyU0ZXeUo3?=
 =?utf-8?B?clI4RHJGS1hrVzdXTnIzamlsd2RISEtKYVVxNUZGcTBQdXhwdGsyQjduYkNy?=
 =?utf-8?B?dklmMHJQbG91K2FpRlpaUUtaVUFPUUNycDBicW4va1ovb1BRNmxpQlZ3aW8x?=
 =?utf-8?B?WUxKWDNmU25CWE5sY1VUUWxFZ3g3RndjSnB1emtEMlI4REFESkRKbDhrM0Ra?=
 =?utf-8?B?T0pXUVNXSDVlYTJYcCtPU2pRQ2ladXd3YkRsSU9KQXkxT3I4MjE3SEgrOVhr?=
 =?utf-8?B?NS9ZUEJEMkVRS3ZBaTlETzdQMUdrS1BkaUNhdkJ3NXp4QjlLSVkvSlJ3c09z?=
 =?utf-8?B?MENLeEVjK2duU1VNdmtKcDlpZU00cDhHY2lWc3o0T04zRlg5TXJ1YnkreThK?=
 =?utf-8?B?d1ovcy9KYnBTNGtNSXNIZ2VEdVRtNlBtRVhGTzg3Y1RpNjdsSGpQbThDb0c0?=
 =?utf-8?B?YzM0K3VJaytNQUlPajJxV0JoMVZOTm8zMjhOck1mMDlmR0NmZFhnUlhsMUF1?=
 =?utf-8?B?QUE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: e90d6e89-0dcb-44d7-243c-08dbefb3c5b4
X-MS-Exchange-CrossTenant-AuthSource: LV3PR11MB8603.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Nov 2023 01:45:59.9400
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: wZRUh/W+CoAzY6WeZwj1rYKupV/j4ezOD3See93pUkTfX6LowhxPM9fX7QsexGk4SmmPsjtE6lVqvYrsxn+KPg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR11MB7005
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on pete.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (pete.vger.email [0.0.0.0]); Mon, 27 Nov 2023 17:46:22 -0800 (PST)

hi, Yosry Ahmed,

On Mon, Nov 27, 2023 at 01:13:44PM -0800, Yosry Ahmed wrote:
> On Wed, Nov 22, 2023 at 5:54 AM kernel test robot <oliver.sang@intel.com> wrote:
> >
> >
> >
> > Hello,
> >
> > kernel test robot noticed a -30.2% regression of will-it-scale.per_thread_ops on:
> >
> >
> > commit: c7fbfc7b4e089c4a9b292b1973a42a5761c1342f ("[PATCH v3 3/5] mm: memcg: make stats flushing threshold per-memcg")
> > url: https://github.com/intel-lab-lkp/linux/commits/Yosry-Ahmed/mm-memcg-change-flush_next_time-to-flush_last_time/20231116-103300
> > base: https://git.kernel.org/cgit/linux/kernel/git/akpm/mm.git mm-everything
> > patch link: https://lore.kernel.org/all/20231116022411.2250072-4-yosryahmed@google.com/
> > patch subject: [PATCH v3 3/5] mm: memcg: make stats flushing threshold per-memcg
> >
> > testcase: will-it-scale
> > test machine: 104 threads 2 sockets (Skylake) with 192G memory
> > parameters:
> >
> >         nr_task: 50%
> >         mode: thread
> >         test: fallocate2
> >         cpufreq_governor: performance
> >
> >
> 
> This regression was also reported in v2, and I explicitly mention it
> in the cover letter here:
> https://lore.kernel.org/lkml/20231116022411.2250072-1-yosryahmed@google.com/

got it. this also reminds us to read cover letter for a patch set in the
future. Thanks!

> 
> In a nutshell, I think this microbenchmark regression does not
> represent real workloads. On the other hand, there are demonstrated
> benefits on real workloads from this series in terms of stats reading
> time.
> 

ok, if there are future versions of this patch, or when it is merged, we will
ignore similar results.

just a small question, since we focus on microbenchmark, if we found other
regression (or improvement) on tests other than will-it-scale::fallocate,
do you want us to send report or just ignore them, either?