Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 27 Apr 2020 10:24:21 -0700
From:   Roman Gushchin <guro@fb.com>
To:     Johannes Weiner <hannes@cmpxchg.org>
CC:     Yang Yingliang <yangyingliang@huawei.com>, <tj@kernel.org>,
        <lizefan@huawei.com>, <cgroups@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <wangkefeng.wang@huawei.com>,
        <linux-mm@kvack.org>, <guro@cmpxchg.org>
Subject: Re: memleak in cgroup
Message-ID: <20200427172421.GA122591@carbon.DHCP.thefacebook.com>
References: <6e4d5208-ba26-93ed-c600-4776fc620456@huawei.com>
 <34dfdb52-6efd-7b11-07c8-9461a13b3aa4@huawei.com>
 <20200427171304.GC29022@cmpxchg.org>
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20200427171304.GC29022@cmpxchg.org>
MIME-Version: 1.0
X-MS-Exchange-MessageSentRepresentingType: 1
Received: from carbon.DHCP.thefacebook.com (2620:10d:c090:400::5:90e0) by MWHPR19CA0075.namprd19.prod.outlook.com (2603:10b6:320:1f::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2937.13 via Frontend Transport; Mon, 27 Apr 2020 17:24:25 +0000
X-Originating-IP: [2620:10d:c090:400::5:90e0]
X-MS-PublicTrafficType: Email
X-MS-Office365-Filtering-Correlation-Id: 688fbeef-d988-48fe-52cc-08d7eacfd5a1
X-MS-TrafficTypeDiagnostic: BYAPR15MB2872:
X-Microsoft-Antispam-PRVS: <BYAPR15MB28725F0FD9CE501B024C1129BEAF0@BYAPR15MB2872.namprd15.prod.outlook.com>
X-FB-Source: Internal
X-MS-Oob-TLC-OOBClassifiers: OLM:8882;
X-Forefront-PRVS: 0386B406AA
X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR15MB4136.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFTY:;SFS:(346002)(39860400002)(366004)(396003)(376002)(136003)(66946007)(478600001)(86362001)(66556008)(6916009)(186003)(16526019)(5660300002)(6506007)(316002)(53546011)(66476007)(6666004)(3480700007)(8676002)(52116002)(7696005)(55016002)(2906002)(7116003)(33656002)(1076003)(4326008)(8936002)(9686003)(81156014);DIR:OUT;SFP:1102;
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: H9ZKxph5U/2XcW7OtxoPshwE3wHm6bBBxdk1xA205rtcT+HKkjIpFjbkhR2DgDF7Oe4YqBI7SOgAR1atXo1htEkGzf6e1bhjanYnH5kMiIh5I+wAq4bGOIjVho+W24VdjYMDnb8+vTBT5jnKtNc7OGt7AX5Ni8QXVhc5n/CZq01s9KYvRT/M3lFMbJbjaZUgDS0kdmzRmtar+A4JK0TZSBmIAOG358iOOMHJ+lchWWlqSzcURlWOJfcSxKpQ1QTaMvtiPgQkX8MWAjpodRa1EE+SmpUCpuJ2WDh/vLZKuEf+xnvG4HSm6bbEZXhF1mlqHLkMi3Gv1MDYxkOV2c25uI8dhADBHLO0tXq/fo3Wld/hfw9DnhJaE3SHsD4tiYeq8MypyGrMVOAL/IBdIUI+fybWkuM7XW34/1DG0U3op4I8BiV2loRd86qjtQ5PQBly
X-MS-Exchange-AntiSpam-MessageData: 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
X-MS-Exchange-CrossTenant-Network-Message-Id: 688fbeef-d988-48fe-52cc-08d7eacfd5a1
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Apr 2020 17:24:26.0623
 (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: EVV3d9UgIVhTo4B14aZZiGdA1IDfsb47JFZfLeyHzHVeg4D/RVIvdjxU3e+jpDSN
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2872
X-OriginatorOrg: fb.com
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676
 definitions=2020-04-27_12:2020-04-27,2020-04-27 signatures=0
X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501
 mlxscore=0 malwarescore=0 bulkscore=0 phishscore=0 clxscore=1011
 mlxlogscore=923 spamscore=0 lowpriorityscore=0 impostorscore=0
 suspectscore=5 adultscore=0 classifier=spam adjust=0 reason=mlx
 scancount=1 engine=8.12.0-2003020000 definitions=main-2004270143
X-FB-Internal: deliver
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Apr 27, 2020 at 01:13:04PM -0400, Johannes Weiner wrote:
> +cc Roman who has been looking the most at this area
> 
> On Mon, Apr 27, 2020 at 03:48:13PM +0800, Yang Yingliang wrote:
> > +cc linux-mm@kvack.org <mailto:linux-mm@kvack.org>
> > 
> > On 2020/4/26 19:21, Yang Yingliang wrote:
> > > Hi,
> > > 
> > > When I doing the follow test in kernel-5.7-rc2, I found mem-free is
> > > decreased
> > > 
> > > #!/bin/sh
> > > cd /sys/fs/cgroup/memory/
> > > 
> > > for((i=0;i<45;i++))
> > > do
> > > ??????? for((j=0;j<60000;j++))
> > > ??????? do
> > > ??????????????? mkdir /sys/fs/cgroup/memory/yyl-cg$j
> > > ??????? done
> > > ??????? sleep 1
> > > ??????? ls /sys/fs/cgroup/memory/ | grep yyl | xargs rmdir
> > > done
> 
> Should be easy enough to reproduce, thanks for the report. I'll try to
> take a look later this week, unless Roman beats me to it.
> 
> Is this a new observation in 5.7-rc2?
> 
> Can you provide /sys/fs/cgroup/unified/cgroup.stat after the test?

I'm actually trying to reproduce it now, but so far haven't found any issues.

Yang, can you, please, attach the config you're using?

And also confirm that you're giving the system some time before looking
at the memory statistics? Reclaim of internal cgroup structure is a complex
process which might take some time to finish.

Is dmesg also clean?

Thanks!