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Thu, 3 Dec 2020 20:08:30 +0000 Date: Thu, 3 Dec 2020 12:08:20 -0800 From: Roman Gushchin To: Yang Shi CC: Kirill Tkhai , Shakeel Butt , Dave Chinner , Johannes Weiner , Michal Hocko , Andrew Morton , Linux MM , Linux FS-devel Mailing List , Linux Kernel Mailing List Subject: Re: [PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered Message-ID: <20201203200820.GC1571588@carbon.DHCP.thefacebook.com> References: <20201202182725.265020-1-shy828301@gmail.com> <20201202182725.265020-5-shy828301@gmail.com> <20201203030104.GF1375014@carbon.DHCP.thefacebook.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Originating-IP: [2620:10d:c090:400::5:506c] X-ClientProxiedBy: MWHPR22CA0072.namprd22.prod.outlook.com (2603:10b6:300:12a::34) 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::5:506c) by MWHPR22CA0072.namprd22.prod.outlook.com (2603:10b6:300:12a::34) 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?JVNcVVVJKIkVlVS2OfxMj2y9kBhazmvYlwCUG5C6ghEBg7gNzMocmlV9nU7A?= =?us-ascii?Q?S8nFNAnXIvf4b7jkK1Of3O12gHQ1HRZuKfAiIR0pHenuV3iKn4TzXpn/fjCK?= =?us-ascii?Q?miXP9lXci7+qUrTYEEe8luAsZlYdyXMjTvHv5cTPnpXyUcHgrJcgGfdrXlqk?= =?us-ascii?Q?pwCwdbPQdXO8W74LzkFmBsVaBzCde5E0x870WMyd+GiojFJhSBPUeUNmeV9k?= =?us-ascii?Q?Chlj8Un8OuT1wvWmNqE8I7hf+EBJBxO2LKPkDupDcxr95FnsLY9nDHjLm0ny?= =?us-ascii?Q?uQNOHUh5BH0jPptC5cm1Vj47jUQN3G50NVDJjutdXLO2juzRHmAOaUDZilV2?= =?us-ascii?Q?RFcsXGPQONXLotJYP/upUM5rLYRlGbmV0ct+lDYvKetNZO5qa+TRO6ZlZH/x?= =?us-ascii?Q?B5VLQplN+KIfs5LOGQOiZgLSOzj1MbpYEEUn+oqwDIp2ITJXFOvrFCKjl2dO?= =?us-ascii?Q?Tf6OZIQOYmbLzyx8QZq3oLz9ZhvbO1zNH3MlKWz0tx5Y4RFteojA+lI7FtRP?= =?us-ascii?Q?qhUU2GvFAHtcC5vI47yuQmsClcW09PG2oBKq85L4JtbydMXoty9SHtdlRcJ4?= =?us-ascii?Q?Eknh98OedrJRmoyPmbHrQBLuls85H+0tZSch4w02aTn1Hs4dc2Q7g2ZmVHmM?= =?us-ascii?Q?8c9khG7fg6ETaY9Rd87+FzKwXZf0MJIcDDf4+aHD/2S84V5taJqYOt+qp/zS?= =?us-ascii?Q?Lzcfj78ENmtL/8e6mQYiQJX4YPGBacjIzdR1TBGQ62MaNHNtt3P/GASLuivy?= =?us-ascii?Q?SVNPtAT1ag438Rqfh7Of3WobMYpq+Fa+bIBHxFUGBzZZ5R2p4DRmEj17DiI8?= =?us-ascii?Q?/UigE598iecLTBwdjpEHZZ2FcbLlwRT4paybEBLPxltuHvoxjnDzrtnj1lh/?= =?us-ascii?Q?N68sZElwbtn9YL6Unt7AN0h7dIH1WFewTepVyB49u34OtmkO/w2MFypYH+fY?= =?us-ascii?Q?TsZJxiiX75z7Hft0pfQER/3M93lT4cfY0gGodq1y5I2sJgyv6bDYoBZvgMpd?= =?us-ascii?Q?2khWNqQcN13n30zlQs5G904aGw=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 87d903b2-603e-4bf2-a491-08d897c73456 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Dec 2020 20:08:30.7613 (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: /gslv5eZkY/0ZFLzQbjGrBtLRXOY97IUecs/ZE7YVlLb228IbSrWSIc/S2TcSuRP X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2630 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-03_11:2020-12-03,2020-12-03 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-2012030116 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 08:59:40PM -0800, Yang Shi wrote: > On Wed, Dec 2, 2020 at 7:01 PM Roman Gushchin wrote: > > > > 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. > > I thought about this too. But I was not convinced by myself that > messing flags with state is a good practice. We may add more flags in > the future, so we may end up having something like: > > flag > flag > flag > state > flag > flag > ... > > Maybe we could use the highest bit for state? Or just state flag flag flag flag flag ... ?