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Fri, 3 Jul 2020 15:50:24 +0000 Date: Fri, 3 Jul 2020 08:50:21 -0700 From: Roman Gushchin To: Shakeel Butt CC: Michal Hocko , Johannes Weiner , Yang Shi , David Rientjes , Greg Thelen , Andrew Morton , Linux MM , LKML , Cgroups Subject: Re: [RFC PROPOSAL] memcg: per-memcg user space reclaim interface Message-ID: <20200703155021.GB114903@carbon.dhcp.thefacebook.com> References: <20200702152222.2630760-1-shakeelb@google.com> <20200703063548.GM18446@dhcp22.suse.cz> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: BY5PR17CA0029.namprd17.prod.outlook.com (2603:10b6:a03:1b8::42) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.dhcp.thefacebook.com (2620:10d:c090:400::5:93e7) by BY5PR17CA0029.namprd17.prod.outlook.com (2603:10b6:a03:1b8::42) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3153.27 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: b068f59a-963c-4cc0-6067-08d81f68cc8d X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jul 2020 15:50:24.3181 (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: g5O0ZX6NyuR5e0FeAKzjJ0ie3fJdhCK7bH3mYkrUtZICnyrPfxLzIR+qKx7S2IY7 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2630 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-03_10:2020-07-02,2020-07-03 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 clxscore=1011 bulkscore=0 impostorscore=0 priorityscore=1501 suspectscore=1 spamscore=0 mlxlogscore=837 cotscore=-2147483648 adultscore=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007030108 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 03, 2020 at 07:23:14AM -0700, Shakeel Butt wrote: > On Thu, Jul 2, 2020 at 11:35 PM Michal Hocko wrote: > > > > On Thu 02-07-20 08:22:22, Shakeel Butt wrote: > > [...] > > > Interface options: > > > ------------------ > > > > > > 1) memcg interface e.g. 'echo 10M > memory.reclaim' > > > > > > + simple > > > + can be extended to target specific type of memory (anon, file, kmem). > > > - most probably restricted to cgroup v2. > > > > > > 2) fadvise(PAGEOUT) on cgroup_dir_fd > > > > > > + more general and applicable to other FSes (actually we are using > > > something similar for tmpfs). > > > + can be extended in future to just age the LRUs instead of reclaim or > > > some new use cases. > > > > Could you explain why memory.high as an interface to trigger pro-active > > memory reclaim is not sufficient. Also memory.low limit to protect > > latency sensitve workloads? I initially liked the proposal, but after some thoughts I've realized that I don't know a good use case where memory.high is less useful. Shakeel, what's the typical use case you thinking of? Who and how will use the new interface? > > Yes, we can use memory.high to trigger [proactive] reclaim in a memcg > but note that it can also introduce stalls in the application running > in that memcg. Let's suppose the memory.current of a memcg is 100MiB > and we want to reclaim 20MiB from it, we can set the memory.high to > 80MiB but any allocation attempt from the application running in that > memcg can get stalled/throttled. I want the functionality of the > reclaim without potential stalls. But reclaiming some pagecache/swapping out anon pages can always generate some stalls caused by pagefaults, no? Thanks!