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Mon, 24 Feb 2020 16:58:01 +0000 Date: Mon, 24 Feb 2020 08:57:50 -0800 From: Roman Gushchin To: Christopher Lameter CC: Wen Yang , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Xunlei Pang , , Subject: Re: [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU_PARTIAL Message-ID: <20200224165750.GA478187@carbon.dhcp.thefacebook.com> References: <20200222092428.99488-1-wenyang@linux.alibaba.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MWHPR17CA0087.namprd17.prod.outlook.com (2603:10b6:300:c2::25) To BYAPR15MB2631.namprd15.prod.outlook.com (2603:10b6:a03:150::19) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.dhcp.thefacebook.com (2620:10d:c090:500::5:ee6) by MWHPR17CA0087.namprd17.prod.outlook.com (2603:10b6:300:c2::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2750.18 via Frontend Transport; Mon, 24 Feb 2020 16:58:00 +0000 X-Originating-IP: [2620:10d:c090:500::5:ee6] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 978567b5-6c45-4df6-a219-08d7b94ab4fd X-MS-TrafficTypeDiagnostic: BYAPR15MB2472: X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:3826; X-Forefront-PRVS: 032334F434 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(346002)(366004)(396003)(39860400002)(136003)(376002)(189003)(199004)(33656002)(6666004)(6916009)(2906002)(316002)(81166006)(8676002)(54906003)(81156014)(4326008)(86362001)(5660300002)(8936002)(16526019)(186003)(6506007)(9686003)(55016002)(1076003)(66556008)(478600001)(66476007)(66946007)(52116002)(7696005);DIR:OUT;SFP:1102;SCL:1;SRVR:BYAPR15MB2472;H:BYAPR15MB2631.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A:1; Received-SPF: None (protection.outlook.com: fb.com does not designate permitted sender hosts) X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: rogg/I0puHduQmEtZe4JbRL0rC33ffrzOUBQ8LKIvqylOfrmO2GvtzWmMRgFXgoCuTngageQWelMmu+70ZDtnyy5tBx3COvxb+DgCP8X3pFn88SXp1LkYrCISP6xyeEQZAn766I8uatYYsWlifp2tFJZctQDbglDhjvmbCtG+koxHPp4afPYLgeJ0psSvGrmwLvlc6an7oINxL/WJT+Nhc+n6FIG/ynh8wI/BdievhUWktMezShAp3O3gvIcxzZPj583OfSLsmg4KOtgi8YPmzEXAHGyS1eprmPuEPqxwsEnY8UsoQt0cX/tgddbmpNQF8kk1uJlpJRbtLCDqzJKqjlf/fVm2DpUw1qpbDmGn2Mr+Q7Kcp8B5NHfYCJHRnQxeuUdWZEuTjJAL1dXV9HQsEbDXKGvucmIu1OId0ZWmVd7RBZMNoRQzAs7i9BOlYUE X-MS-Exchange-AntiSpam-MessageData: VUUktkCO8ePt7ZOjV3OaK+GuXXbEbIrXuemFtRazX/43EVnuCGHjd+judStzFiyRivNBbI3gPXuObTu4vwFgTLEhYi4vTmSepQVAj833sS9dHkaWUW9fv7E1i20UCz9ylmLJuaux05WmDcEEpUApUMnazV87UiPxpSgwqdFcvsJyAdMLxn2OjjurzCRWUEKQ X-MS-Exchange-CrossTenant-Network-Message-Id: 978567b5-6c45-4df6-a219-08d7b94ab4fd X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Feb 2020 16:58:01.3982 (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: lA8dFl/LEtY+dYPLHEqOaf3Ec2ttMQMFgxi3iPYcREGMSzXyggFxO2QzccBt5uOe X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2472 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-24_07:2020-02-21,2020-02-24 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 mlxlogscore=591 spamscore=0 adultscore=0 phishscore=0 impostorscore=0 bulkscore=0 suspectscore=5 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002240130 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 Mon, Feb 24, 2020 at 01:29:09AM +0000, Christoph Lameter wrote: > On Sat, 22 Feb 2020, Wen Yang wrote: Hello, Christopher! > > > We also observed that in this scenario, CONFIG_SLUB_CPU_PARTIAL is turned > > on by default, and count_partial() is useless because the returned number > > is far from the reality. > > Well its not useless. Its just not counting the partial objects in per cpu > partial slabs. Those are counted by a different counter it. Do you mean CPU_PARTIAL_ALLOC or something else? "useless" isn't the most accurate wording, sorry for that. The point is that the number of active objects displayed in /proc/slabinfo is misleading if percpu partial lists are used. So it's strange to pay for it by potentially slowing down concurrent allocations. > > > Therefore, we can simply return 0, then nr_free is also 0, and eventually > > active_objects == total_objects. We do not introduce any regression, and > > it's preferable to show the unrealistic uniform 100% slab utilization > > rather than some very high but incorrect value. > > I suggest that you simply use the number of partial slabs and multiply > them by the number of objects in a slab and use that as a value. Both > values are readily available via /sys/kernel/slab/<...>/ So maybe something like this? @@ -5907,7 +5907,9 @@ void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo) for_each_kmem_cache_node(s, node, n) { nr_slabs += node_nr_slabs(n); nr_objs += node_nr_objs(n); +#ifndef CONFIG_SLUB_CPU_PARTIAL nr_free += count_partial(n, count_free); +#endif } sinfo->active_objs = nr_objs - nr_free; Thank you!