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Wed, 18 Nov 2020 19:46:24 +0000 Date: Wed, 18 Nov 2020 11:46:20 -0800 From: Roman Gushchin To: Shakeel Butt CC: Johannes Weiner , Michal Hocko , Andrew Morton , , Subject: Re: [PATCH] memcg, kmem: further deprecate kmem.limit_in_bytes Message-ID: <20201118194620.GD186396@carbon.dhcp.thefacebook.com> References: <20201118175726.2453120-1-shakeelb@google.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201118175726.2453120-1-shakeelb@google.com> X-Originating-IP: [2620:10d:c090:400::5:438f] X-ClientProxiedBy: MWHPR22CA0069.namprd22.prod.outlook.com (2603:10b6:300:12a::31) 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::5:438f) by MWHPR22CA0069.namprd22.prod.outlook.com (2603:10b6:300:12a::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3589.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: ffe23841-3a24-49b9-4af3-08d88bfaa1d2 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Nov 2020 19:46:24.7552 (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: y1vb9MMLnUBdQ7sReI+Ot23HNeYUPlXpfZUJx7cZyUP2lUJx34U9ikaZ3xiWCK2C X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2759 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-18_08:2020-11-17,2020-11-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=1 bulkscore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 mlxlogscore=999 priorityscore=1501 clxscore=1015 phishscore=0 spamscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011180137 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 18, 2020 at 09:57:26AM -0800, Shakeel Butt wrote: > The deprecation process of kmem.limit_in_bytes started with the commit > 0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also > explains in detail the motivation behind the deprecation. To summarize, > it is the unexpected behavior on hitting the kmem limit. This patch > moves the deprecation process to the next stage by disallowing to set > the kmem limit. In future we might just remove the kmem.limit_in_bytes > file completely. > > Signed-off-by: Shakeel Butt The first stage was done over a year ago, so if there were no complains it feels like it's a good time to move forward. Acked-by: Roman Gushchin The only question I have is if it's better to return -EINVAL or -ENOTSUPP. The latter option could be more convenient for userspace, because it will be clear that the kernel is not supporting the functionality, rather than the passed value is incorrect (e.g. if the value is read from a config, provided by a user). I'm not sure though, just an idea. Thanks!