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Sat, 17 Aug 2019 19:15:23 +0000 From: Roman Gushchin To: Greg KH CC: Andrew Morton , "linux-mm@kvack.org" , Michal Hocko , Johannes Weiner , "linux-kernel@vger.kernel.org" , Kernel Team , "stable@vger.kernel.org" , Yafang Shao Subject: Re: [PATCH] Partially revert "mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones" Thread-Topic: [PATCH] Partially revert "mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones" Thread-Index: AQHVVJVnJCTepTfXpE2m8ikuyJkTSKb+4vkAgADUEgA= Date: Sat, 17 Aug 2019 19:15:23 +0000 Message-ID: <20190817191518.GB11125@castle> References: <20190817004726.2530670-1-guro@fb.com> <20190817063616.GA11747@kroah.com> In-Reply-To: <20190817063616.GA11747@kroah.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: MWHPR1701CA0012.namprd17.prod.outlook.com (2603:10b6:301:14::22) To DM6PR15MB2635.namprd15.prod.outlook.com (2603:10b6:5:1a6::24) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [2620:10d:c090:180::61b1] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 3dca784f-2915-4a71-6726-08d723474093 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:DM6PR15MB2569; 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charset="us-ascii" Content-ID: <0467F09FF93E174C859D845E827A4C37@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 3dca784f-2915-4a71-6726-08d723474093 X-MS-Exchange-CrossTenant-originalarrivaltime: 17 Aug 2019 19:15:23.1135 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 6mPtGVpZ0ZdJnOfRrtBxC28DNZjVrHiBTsKoXAXrXvLXC1Ikj28wJR///rX4BxrC X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR15MB2569 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-17_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=760 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908170209 X-FB-Internal: deliver X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Aug 17, 2019 at 08:36:16AM +0200, Greg KH wrote: > On Fri, Aug 16, 2019 at 05:47:26PM -0700, Roman Gushchin wrote: > > Commit 766a4c19d880 ("mm/memcontrol.c: keep local VM counters in sync > > with the hierarchical ones") effectively decreased the precision of > > per-memcg vmstats_local and per-memcg-per-node lruvec percpu counters. > >=20 > > That's good for displaying in memory.stat, but brings a serious regress= ion > > into the reclaim process. > >=20 > > One issue I've discovered and debugged is the following: > > lruvec_lru_size() can return 0 instead of the actual number of pages > > in the lru list, preventing the kernel to reclaim last remaining > > pages. Result is yet another dying memory cgroups flooding. > > The opposite is also happening: scanning an empty lru list > > is the waste of cpu time. > >=20 > > Also, inactive_list_is_low() can return incorrect values, preventing > > the active lru from being scanned and freed. It can fail both because > > the size of active and inactive lists are inaccurate, and because > > the number of workingset refaults isn't precise. In other words, > > the result is pretty random. > >=20 > > I'm not sure, if using the approximate number of slab pages in > > count_shadow_number() is acceptable, but issues described above > > are enough to partially revert the patch. > >=20 > > Let's keep per-memcg vmstat_local batched (they are only used for > > displaying stats to the userspace), but keep lruvec stats precise. > > This change fixes the dead memcg flooding on my setup. > >=20 > > Fixes: 766a4c19d880 ("mm/memcontrol.c: keep local VM counters in sync w= ith the hierarchical ones") > > Signed-off-by: Roman Gushchin > > Cc: Yafang Shao > > Cc: Johannes Weiner > > --- > > mm/memcontrol.c | 8 +++----- > > 1 file changed, 3 insertions(+), 5 deletions(-) >=20 > >=20 > This is not the correct way to submit patches for inclusion in the > stable kernel tree. Please read: > https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.ht= ml > for how to do this properly. Oh, I'm sorry, will read and follow next time. Thanks! >=20 >