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Sat, 25 Apr 2020 02:46:30 +0000 Date: Fri, 24 Apr 2020 19:46:25 -0700 From: Roman Gushchin To: Christopher Lameter CC: Andrew Morton , Johannes Weiner , Michal Hocko , , , Subject: Re: [PATCH v3 04/19] mm: slub: implement SLUB version of obj_to_index() Message-ID: <20200425024625.GA107755@carbon.lan> References: <20200422204708.2176080-1-guro@fb.com> <20200422204708.2176080-5-guro@fb.com> <20200423000530.GA63356@carbon.lan> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MWHPR21CA0067.namprd21.prod.outlook.com (2603:10b6:300:db::29) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.lan (2620:10d:c090:400::5:1973) by MWHPR21CA0067.namprd21.prod.outlook.com (2603:10b6:300:db::29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2958.10 via Frontend Transport; Sat, 25 Apr 2020 02:46:29 +0000 X-Originating-IP: [2620:10d:c090:400::5:1973] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 5b14eef9-eaaf-4779-c3b0-08d7e8c2db5c X-MS-TrafficTypeDiagnostic: BYAPR15MB3079: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:6790; 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> > > > unsigned int size; /* The size of an object including metadata */ > > > > unsigned int object_size;/* The size of an object without metadata */ > > > > + struct reciprocal_value reciprocal_size; > > > > > > > > > This needs to be moved further back since it is not an item that needs to > > > be cache hot for the hotpaths. > > > > It could be relatively hot, because it's accessed for reading on every > > accounted allocation. > > The patch seems to only use it for setup and debugging? It is used for > every "accounted" allocation???? Where? And what is an "accounted" > allocation? > > Please, take a look at the whole series: https://lore.kernel.org/linux-mm/20200422204708.2176080-1-guro@fb.com/T/#t I'm sorry, I had to cc you directly for the whole thing. Your feedback will be highly appreciated. It's used to calculate the offset of the memcg pointer for every slab object which is charged to a memory cgroup. So it must be quite hot. Thanks! Roman