Date:   Tue, 11 Jan 2022 10:09:52 -0800
From:   Roman Gushchin <guro@fb.com>
To:     Wei Yang <richard.weiyang@gmail.com>
CC:     <hannes@cmpxchg.org>, <mhocko@kernel.org>,
        <vdavydov.dev@gmail.com>, <akpm@linux-foundation.org>,
        <shakeelb@google.com>, <vbabka@suse.cz>, <willy@infradead.org>,
        <songmuchun@bytedance.com>, <shy828301@gmail.com>,
        <surenb@google.com>, <linux-kernel@vger.kernel.org>,
        <cgroups@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [PATCH 3/4] mm/memcg: retrieve parent memcg from css.parent
Message-ID: <Yd3H8Hea6dBlkzeW@carbon.dhcp.thefacebook.com>
References: <20220111010302.8864-1-richard.weiyang@gmail.com>
 <20220111010302.8864-3-richard.weiyang@gmail.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20220111010302.8864-3-richard.weiyang@gmail.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?/R4Tji1HxQNZMDhjuqAj6vawx8P7kNWmRwxJiSb06sj7fl1K1/L+dVo6q/++?=
 =?us-ascii?Q?IXb3DY1LQPWq2XUBbSJhlbUupWB1pWmu/zeiR/dbbuItAJ8I62bGhahYbvOg?=
 =?us-ascii?Q?UwLgc9PdWx7XUiNgLz0mCYmOAVLsBDbxR0pkN7aMrOg+vfL56CUy1CFFmcwS?=
 =?us-ascii?Q?rmaQ+/S8tXlurivHOmr9UF5/OPbrLnAtBGocO2U32dpHIwjpaE8CLwjzIu+O?=
 =?us-ascii?Q?3caZ4Daxg1jZXqwwDtzcXImBrPST10HtI51Bs2jAxpfdos+SJJafeGk6T6rd?=
 =?us-ascii?Q?QMfmf46PEWuDw4icWxfvEsdNK65/ZVzW7nn7RTKvzexJvJERh1UF8Fqmx92j?=
 =?us-ascii?Q?E7Ska7Lg1I/5MnuE5eFx1FegUPFymPLUP9ikS1mQh3d5Jh8zu21x3mh+meNz?=
 =?us-ascii?Q?fhXv7TIX1Qd4yY6JXhX/K5hRwOlM2j+xSpTnQMtWbebhhI9Zj7YWNwJ7cXOt?=
 =?us-ascii?Q?jQFydeeLq7gZ+LldgqYrKT6EcRHHp8QJlK5KO3Ueik/MvktR1i7P0xCoCwM8?=
 =?us-ascii?Q?j0aj1E4/murlLA0C2ZL0qs1WFO92+g1eEgmYTCoLFCPvwsjzjAOfZwEPrYUq?=
 =?us-ascii?Q?KA4zbMuFbPmelse5LV2WpDM/ncY+BOvhdvcjS8jbIcoMz0lSq/yX2qNt8qEc?=
 =?us-ascii?Q?LkmvObNTdiZpLFwwQJq+t2g6D+GYx+sNMr0BlN/7y38AIMo1+J4PVhu/aQM/?=
 =?us-ascii?Q?Dog7Jaijzenef5i2iFxFRpRHLfayDhTUrkGLphOv2/IfmaAAyAtqMI/BiIGG?=
 =?us-ascii?Q?7mCHFMoYZrX2bFY1MXJOe7SgTwAIIPu4jSXOuYyVZlwQTcWKN52bZ+pTNw9t?=
 =?us-ascii?Q?dpkuK1JAJBK0htCeKyblmIRqGXhUfsNlnJ9oiBUxRbMg9J0aIQ3dAnH7dvdm?=
 =?us-ascii?Q?uMTa67symO+7q0EhwLZ9CPTPZg+Dfxwb2oxH1j6aCPe21O2HxY5hOR7v2imP?=
 =?us-ascii?Q?rZ2HVimY0ROrDb5KW1xpkDsgFyhhvtZegLJ6KiiVv/A0a4TdthQnc1kj+Q7W?=
 =?us-ascii?Q?APmnZyODuAmBKdkIwIyp/yOioGeJvRTKbe/T7d3DIV4wVo9cOoKMfj6FBNOr?=
 =?us-ascii?Q?ne9TveZz/VAj6beZ72VLxSBZ5FcYQSlWSxvUKsB+/pt0JbKCqJuhB+NjPu2Z?=
 =?us-ascii?Q?uzhSSxI8+N7fpHPZGYQ7PJ7RKOV225taN4/7MTh4V2awpbjyTzm4npO7L3O5?=
 =?us-ascii?Q?+jhiXj3Z5KlBajxAlzDugRU4bPFxupuzlEaXPW9M9DReU7R2bxiV+9p8Ws5+?=
 =?us-ascii?Q?53sJ0XqjnWiywQodLLdH40Ups6rSMji1/OHJSjqXXdmqjmkqHFnjBmjhPpmG?=
 =?us-ascii?Q?+0ChoVMN95YVP6nQS2PYvD2seGmMdk0xdnM2k5ONLj1FNAe/pYduyvgsRuyw?=
 =?us-ascii?Q?vjeosPU7FOB9oEzxA/Uw/kFo5nz+4BavHWTlwhGQPogz4w4GREf1Ssspz3kH?=
 =?us-ascii?Q?M1OXLB5lUmIvCor5LAnRVvYOwcvQq7QcyGvAw/Nk05WMBa0OflmeilGcn3oU?=
 =?us-ascii?Q?Z6VcTVNZuCi8PYJCVcTOyJFyv4ovpuucYi5ze3HWT2vKOfIW6oHT51g4dLlX?=
 =?us-ascii?Q?DBmyvj9bIak4JO0GO5NLBwqnpNJ1di5DjBn9gG6L?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 47701baa-87f9-4bb0-35ab-08d9d52d92e6
X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jan 2022 18:09:56.5534
 (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: wlCRZFv+QNTR0sQ4G1frSmijlotVtu+v+k5BNnV8sJvXXVscOsfyIS5k6Lb5X/kf
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2759
X-OriginatorOrg: fb.com
X-Proofpoint-ORIG-GUID: 9lKjd76Xez-u5qC1ZY_W21HZDmJNXl7x
X-Proofpoint-GUID: 9lKjd76Xez-u5qC1ZY_W21HZDmJNXl7x
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513
 definitions=2022-01-11_04,2022-01-11_01,2021-12-02_01
X-Proofpoint-Spam-Details: rule=fb_outbound_notspam policy=fb_outbound score=0 impostorscore=0
 suspectscore=0 adultscore=0 phishscore=0 mlxlogscore=717 bulkscore=0
 lowpriorityscore=0 spamscore=0 priorityscore=1501 mlxscore=0
 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx
 scancount=1 engine=8.12.0-2110150000 definitions=main-2201110099
X-FB-Internal: deliver
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Jan 11, 2022 at 01:03:01AM +0000, Wei Yang wrote:
> The parent we get from page_counter is correct, while this is two
> different hierarchy.
> 
> Let's retrieve the parent memcg from css.parent just like parent_cs(),
> blkcg_parent(), etc.

Does it bring any benefits except consistency?

> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

Reviewed-by: Roman Gushchin <guro@fb.com>

Thanks!