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Thu, 3 Dec 2020 03:01:08 +0000 Date: Wed, 2 Dec 2020 19:01:04 -0800 From: Roman Gushchin To: Yang Shi CC: , , , , , , , , Subject: Re: [PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered Message-ID: <20201203030104.GF1375014@carbon.DHCP.thefacebook.com> References: <20201202182725.265020-1-shy828301@gmail.com> <20201202182725.265020-5-shy828301@gmail.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201202182725.265020-5-shy828301@gmail.com> X-Originating-IP: [2620:10d:c090:400::5:4a99] X-ClientProxiedBy: MWHPR15CA0058.namprd15.prod.outlook.com (2603:10b6:301:4c::20) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.DHCP.thefacebook.com (2620:10d:c090:400::5:4a99) by MWHPR15CA0058.namprd15.prod.outlook.com (2603:10b6:301:4c::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3632.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?x7YyvQpNAe7YuBVEzzeZ0sdsJduvPfywKggzhz+OYI5FeX4OqTM1Kz3AkzbY?= =?us-ascii?Q?ZvmMBEyZIRwJYKnWHD4gyCi/J+HHCjjvSJ6GRuIK9tHjr9cuuJ2KosKFXedq?= =?us-ascii?Q?pWEvRB2eA0CooMb0dFolL5KWu9DjPyHZg39mK2i+9UXz5RS5QETF1WCaoch4?= =?us-ascii?Q?aosVuYuAlMGxfpd15b5pI4h2a22cMnXUUtFjY4ZGC+3WhTfmbCHFzT+BXO74?= =?us-ascii?Q?3XRmh7Gs7dpLmG727kNmE5k3ostgfgWnsv3wFYAC0MCjlbWn1jA3ShFM1GBe?= =?us-ascii?Q?cHosJIeZ4b+A7FJ9XJRVmjiXzHjitsd+Q4fv+mfCUFFlmfAYovST3E/Vt39h?= =?us-ascii?Q?HQtQFgYG6NazvS+Jd+xTCmvx2n4IfQnZgYXGgb6Q3BXA2cfAQlZpyD6MiWUH?= =?us-ascii?Q?iJMzZMoMAX/9O+hBJzjQaThGW0VdIwRcURSTfRFN1H0KL0aXTrU+8fsm69GX?= =?us-ascii?Q?V11wC/iqSx3Gzi9XrZp+W4s3riSCBtiwg6kCd2frMODnSMqerXL4p4X8i3F1?= =?us-ascii?Q?UcekxZwe6Ng/yu7LzpvPYUTP09x0GGhCRnLhS9X4+AtnzMGOZPX3/484auyZ?= =?us-ascii?Q?8KdTWw4wU0D7kHy9NE/i4/Zt2S55gKq7aqdz3asZvRtP0oCDPS5qpRzXT3DF?= =?us-ascii?Q?4/+9uD6DZiDAdw6mQvxO+LxQ/H4CO8KxafFXmMrnlXuSmO++li5YGCWGnMEC?= =?us-ascii?Q?wRGpkHIXUDKXJM/A2XtKj3iTIXe0fnLPXdF0m59xKh5hgxUSQPXZuMTaJ+3S?= =?us-ascii?Q?P6ezP6B8XWOQx+9+qmvuOPgL3bMOYGyxoEttcTCAdGibfugw1udkv8wyA7BO?= =?us-ascii?Q?zFloSnTSk+LSx10kA+oKbNlscuqLbP5CXdWbYN2lcSmprdp1Bimj8owp4CJx?= =?us-ascii?Q?B8+gOQbYDVd1zYLVsesfNKhz60/IHD0ciLBBEBbS2iK3UaIYNoyPEgpNQaHZ?= =?us-ascii?Q?caNbCFNhLeWcE/rzc50lQiqZEG76g/ZMIl7lYJUcOy1opYulpFrB5mfKau4X?= =?us-ascii?Q?0picLk3LmnZJEOoLYnjgm2zxvw=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: dd270963-df12-454f-1cac-08d89737aeec X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Dec 2020 03:01:08.8508 (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: Qk6V4obzCuZxmPugrh5SmFfjk25Z/GBZOTWHjKb4ghPx5wGwvAgJzQ8OnBbEzS/F X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3080 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-03_01:2020-11-30,2020-12-03 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 adultscore=0 clxscore=1015 priorityscore=1501 mlxscore=0 bulkscore=0 lowpriorityscore=0 mlxlogscore=999 malwarescore=0 spamscore=0 suspectscore=5 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012030017 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 Wed, Dec 02, 2020 at 10:27:20AM -0800, Yang Shi wrote: > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > This approach is fine with nr_deferred atthe shrinker level, but the following > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > from unregistering correctly. > > Introduce a new "state" field to indicate if shrinker is registered or not. > We could use the highest bit of flags, but it may be a little bit complicated to > extract that bit and the flags is accessed frequently by vmscan (every time shrinker > is called). So add a new field in "struct shrinker", we may waster a little bit > memory, but it should be very few since there should be not too many registered > shrinkers on a normal system. > > Signed-off-by: Yang Shi > --- > include/linux/shrinker.h | 4 ++++ > mm/vmscan.c | 13 +++++++++---- > 2 files changed, 13 insertions(+), 4 deletions(-) > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index 0f80123650e2..0bb5be88e41d 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -35,6 +35,9 @@ struct shrink_control { > > #define SHRINK_STOP (~0UL) > #define SHRINK_EMPTY (~0UL - 1) > + > +#define SHRINKER_REGISTERED 0x1 > + > /* > * A callback you can register to apply pressure to ageable caches. > * > @@ -66,6 +69,7 @@ struct shrinker { > long batch; /* reclaim batch size, 0 = default */ > int seeks; /* seeks to recreate an obj */ > unsigned flags; > + unsigned state; Hm, can't it be another flag? It seems like we have a plenty of free bits. > > /* These are for internal use */ > struct list_head list; > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 457ce04eebf2..0d628299e55c 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -378,6 +378,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > if (shrinker->flags & SHRINKER_MEMCG_AWARE) > idr_replace(&shrinker_idr, shrinker, shrinker->id); > #endif > + shrinker->state |= SHRINKER_REGISTERED; > up_write(&shrinker_rwsem); > } > > @@ -397,13 +398,17 @@ EXPORT_SYMBOL(register_shrinker); > */ > void unregister_shrinker(struct shrinker *shrinker) > { > - if (!shrinker->nr_deferred) > - return; > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > - unregister_memcg_shrinker(shrinker); > down_write(&shrinker_rwsem); > + if (!shrinker->state) { > + up_write(&shrinker_rwsem); > + return; > + } > list_del(&shrinker->list); > + shrinker->state &= ~SHRINKER_REGISTERED; > up_write(&shrinker_rwsem); > + > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > + unregister_memcg_shrinker(shrinker); > kfree(shrinker->nr_deferred); > shrinker->nr_deferred = NULL; > } > -- > 2.26.2 >