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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?HT69Yh0Z+y0sfT73X/LrQ9SX/hTIUIxhTXONYkaaqJ7VmtEtfX7j2BNGoQtd?= =?us-ascii?Q?TkKQrqI7JHsh4GSutvnKudYA772o/wUuqFoXa3zTvbUwivUGI0rsLLl9bITr?= =?us-ascii?Q?UaQdAqgc8DeHzr6UCAY+F93YZhAdQ4+iomTIPld1/eqeBWV1mk3KRP0Wcaxi?= =?us-ascii?Q?92LgFbG+19gj1RlDHF8y4sZl0xWp0ksp71K1gSXW4xKqag/jbvVtPaPzk3W+?= =?us-ascii?Q?4yctlus2dVrgupWoKybhqvFMdG6J2jXNfAcOM9CnLyAxPB6/KJYh+WZDlwCc?= =?us-ascii?Q?Twhyi+T0/t6Cfa0vbZLRSfliVvv+XSFJcj3MfQOuGvDEWREEiNm8K1yxFngL?= =?us-ascii?Q?qan5/e2jRn2bpTTjH3qhtwII83vZVfogUx5Vd4eeYyxYD0OB2tF/I1dLF17y?= =?us-ascii?Q?wZJuwS2Q8RX5LRq2NU19jEy2suSMHE7Vyg+5PaFQaS2R7m9QSspdI1XFNsg4?= =?us-ascii?Q?r+c0gr0Gxj2ixn3StOx6DDOppwZcgEAt2nwO56IwhGyOLY26j3gTLit/GG+v?= =?us-ascii?Q?T04BeOggaJBxl2Y4rDxW6rtw3NKJ38ACJWBem1iZaprXFHsrtwJPG+i5sh6U?= =?us-ascii?Q?K59f+hxI9nH/X6mDPHEchChKYe1QST1QRysEhQvht/4Waa4JvddAxUNxyZTY?= =?us-ascii?Q?GP9KqjxzZ/Wnz3Tr/Ez5rx+j+6xgfZmsfN+kvJtkI/UQgb94CTpnpZTdVBLs?= =?us-ascii?Q?An8bEiARVehVA6rJaK17PNVTyeDGB9MG27cHt2HCTTRigmfQREW6JFWSZieM?= =?us-ascii?Q?hS0Om0DQlkqgLgzhTAu+Cs/0+LgX9ZkEFMVyDbZ59DueH+Q8yGKWZaxLp3I3?= =?us-ascii?Q?AnU8RnbR9677I3Y1m9zumgJGo9gKqJ2Wr/6QIeQiXX2Xv7gZ/G6pBLuTHpuA?= =?us-ascii?Q?SyigDEW6W3hbimOHKpxFkXovOsFYhsSJyAbIYy6Sy6id9VMogh965A+eljxr?= =?us-ascii?Q?hMH0BCfu9YGUPFmy+3Mnn/fEuGyJykCMcypMtmoQELEa21QdMmu6q3DnuhSa?= =?us-ascii?Q?+OqmBuRXh1vq51O4rRB6TzwMQE5zzpU3Lyf1nxJirvruNrA8dX3HFOG52FZ/?= =?us-ascii?Q?gFX9Ll4yccHFiNkwlLmgrHlbUfi9o6rFmkfEvYtmdxd+WXbS/7+upbW3gf9A?= =?us-ascii?Q?fU94wDor33GcGI61N2fZVfMKophS7km+LiDtD27IkMMi7lXfkaai4tgNsUQe?= =?us-ascii?Q?xPXLkpCPY/03v9Kx3CR+REFdgKYttqkiRT8CCCxUIAzNAHztvRY0OetzZIiD?= =?us-ascii?Q?pCcLgXKrB0cX5McoCETlS+lqwiM9OyeSglo2GL8qDHGu82GDXIEuTBIofBVa?= =?us-ascii?Q?bKgbLs3IaLCphUfzH54Klma40y2VoewCElFIcnJ8ljinUg=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 25e071c9-8ad4-477e-3010-08d961f480f8 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Aug 2021 03:01:41.4908 (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: nYDAchvBHAXyNwlnpJcLQnQLW0YUo52xoBSvYARCHDOQRhK+ci6y/OjPJ8LWDuhk X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR15MB4357 X-OriginatorOrg: fb.com X-Proofpoint-GUID: oJi1R3GgGiepAoWadm2XbI0xzBAVBqg3 X-Proofpoint-ORIG-GUID: oJi1R3GgGiepAoWadm2XbI0xzBAVBqg3 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-18_01:2021-08-17,2021-08-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=999 suspectscore=0 lowpriorityscore=0 mlxscore=0 spamscore=0 clxscore=1011 impostorscore=0 priorityscore=1501 bulkscore=0 phishscore=0 malwarescore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108180017 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 14, 2021 at 01:25:08PM +0800, Muchun Song wrote: > Pagecache pages are charged at the allocation time and holding a > reference to the original memory cgroup until being reclaimed. > Depending on the memory pressure, specific patterns of the page > sharing between different cgroups and the cgroup creation and > destruction rates, a large number of dying memory cgroups can be > pinned by pagecache pages. It makes the page reclaim less efficient > and wastes memory. > > We can convert LRU pages and most other raw memcg pins to the objcg > direction to fix this problem, and then the page->memcg will always > point to an object cgroup pointer. > > Therefore, the infrastructure of objcg no longer only serves > CONFIG_MEMCG_KMEM. In this patch, we move the infrastructure of the > objcg out of the scope of the CONFIG_MEMCG_KMEM so that the LRU pages > can reuse it to charge pages. > > We know that the LRU pages are not accounted at the root level. But > the page->memcg_data points to the root_mem_cgroup. So the > page->memcg_data of the LRU pages always points to a valid pointer. > But the root_mem_cgroup dose not have an object cgroup. If we use > obj_cgroup APIs to charge the LRU pages, we should set the > page->memcg_data to a root object cgroup. So we also allocate an > object cgroup for the root_mem_cgroup. > > Signed-off-by: Muchun Song I like the "move objcg stuff to memcg/css level" part. I'm less convinced about making byte-sized charging kmem-specific (both naming and #ifdef CONFIG_MEMCG_KMEM). Do we really win a lot? I understand why we might wanna compile out some checks from the hot allocation path, but few bytes in struct objcg will not make a big difference, as well as few lines of code in cgroup creation/removal paths. Also it might be useful for byte-sized accounting outside kmem, e.g. zswap. So, I'd remove this dependency and rename to something like obj_cgroup_release_bytes(). In the long run we might wanna to eliminate CONFIG_MEMCG_KMEM completely, so let's at least not add new dependencies. Thanks!