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Shutemov" , Mel Gorman , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Richard Chang , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/4] mm/page_isolation: make page isolation a standalone bit. 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?sc2IY2AfVT1GFyCRZrWDny87xae0boxLdgTV6Yfb/fEVJbJV3WLSfdqeox0i?= =?us-ascii?Q?NK5k0aaX89YL6KJrEiwxJsnv/D2x7rKnJ9R0WYkH8xYjn/j+3tapMxGnwqD5?= =?us-ascii?Q?xxxuVVQEZC3R0PfIuQ7ASC6aKw0IIYnViQRehhj9PlJIKRRZODq2fEtSlwFf?= =?us-ascii?Q?u8JkgKQGjXICn2Hd4ogcvAN1SIZFQd/rbj/13JS6vvRsYlyJpmHX21rvfMIV?= =?us-ascii?Q?r17HCEOlfehnyfx2JU6jgSr8pQfNuNUtO5LLR4BkQMZMjbseNWagKW6vA6Yc?= =?us-ascii?Q?CiZrbzDn4Db4vmcq5L0ved6sWuxVqB2R82J+Uzah+At4IS3c1VPvOdVqLFj6?= =?us-ascii?Q?YN7o4VytW2ryIUhuZ8a1rBu/mxAF9LH7dK4xYIt/NHMFwdS/JEPbp7ey+Ftd?= =?us-ascii?Q?qTtjPTKBakB11K1wq/LhAR8H5BgLmko2hX+DO6X2mbA4qT7vpf6ygAbGmrsu?= =?us-ascii?Q?PUkTyjvgfE5iZKjcaxy569SPR3TndzjAfa+DY1ccsD94YzoISB5YJkqPRj3G?= =?us-ascii?Q?yvSd/xRcY1Vli9DWLYlgt8Zb4kuRwkbcMRSxzr0RuZS7UmTerZcjCyqSOpmG?= =?us-ascii?Q?i0hTKmhTQxu7aqXofH39HaGjCK4Osi1RAO78XykycPGSMjF6QDzARv1HDbzT?= =?us-ascii?Q?2XBr3KvntoE0kOZHjjIcyW00dkjnoDFkAzsCPDtxHsdQ9U6l4Jk3fi/zCd2+?= =?us-ascii?Q?xhVc/SXvrmABNILkRG392IWXMmcq/2fhsLYxy8LBfzY1kCyqmIW3UEZ/FnAr?= =?us-ascii?Q?dADnY2+NOcmUtRMk40DlBGWBUYkJPlQJkDc9Gjz8w6SjjUiDtziwmuNChPIG?= =?us-ascii?Q?Tmy8eA01bZ8MPuKdC3JT8pR4fiQoR4uGsUVqN08vUWs6qEdwj08Ch72m1vmK?= =?us-ascii?Q?2mCLCJsN3Bp6vpTOwSgIMaP+EVnHCMMNIz21keHc6mSreDxSubQywTafJAmn?= =?us-ascii?Q?txMb9paWR/+JxKiR/NSJNqaZtDaCYMm8/HIJ2FgiwFO+lPFScFnQylS1/Hvm?= =?us-ascii?Q?Tvyh/ypt+88dhT7M6T5dqO/q7AyQpJZHOibDoccTk6c/7gY1KSLLLfPb4S1+?= =?us-ascii?Q?1KYRTNElLlaN5jnzZ/+tns4XIghxyaOTON/xDJa2G3Zm6wAT1uMLSt3x5E+0?= =?us-ascii?Q?lgUG5aYdpNaYrAewODeNJdFrI1TifhT8igdxLxUYEy0w0/2DAx6yViSAO87y?= =?us-ascii?Q?n9Q1EhwJvknGSMw7UABb9d7lAWdsUN2t+DQld8T/sjlHuRh8IcBHrrhpe0PV?= =?us-ascii?Q?i6gFu9zUTSIBOJtZRADlwu7Z2Cw7rWiJ2xHabx4vN+bN5acf2OTs0azl8wjp?= =?us-ascii?Q?6RQKgrf3DaM1UZCH0s2GH8SfqPaaueQ14hu9g1ewWFrkZkV3nQcnHlctkHrS?= =?us-ascii?Q?fLybViwLET6Om7bWHPdTBmnRniNRNnRJWmG/2bbbLeekl1g06tqPVxMAa1S8?= =?us-ascii?Q?T0V3mPYsLDGKpM+QV0tKn3Ii/WGGwahn2QBpryl3HuxYfrS5bkEXWgvWR8Ok?= =?us-ascii?Q?0SYEB5/xU68j8RmUF3COSgooXXZv4VnTtnet5OnArKhXlDY9jrQVJRZNbcPn?= =?us-ascii?Q?kEffF8Rcm4501Lh3STo7e74HUY9CK2A11NhEVav4?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8dbd37d9-9ba7-4c4f-5870-08dd96f8d416 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 May 2025 17:16:01.2343 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Lh+WwlWUGWu3GgMKhLU9GBZN2ctQpAYhJDbK7Kkc0bZrwd3Yvb0QqxROyrWOkWq6 X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6934 On 19 May 2025, at 12:42, David Hildenbrand wrote: >>>> +#ifdef CONFIG_MEMORY_ISOLATION >>>> + if (flags & PB_migrate_isolate_bit) >>>> + return MIGRATE_ISOLATE; >>>> +#endif >>> >>> If you call get_pfnblock_flags_mask() with MIGRATETYPE_MASK, how coul= d you ever get PB_migrate_isolate_bit? >> >> MIGRATETYPE_MASK is ((BIT(PB_migratetype_bits) - 1) | PB_migrate_isola= te_bit), >> so it gets PB_migrate_isolate_bit. >> > > Oh ... that's confusing. > >>> >>> >>> I think what we should do is >>> >>> 1) Rename get_pfnblock_flags_mask() to get_pfnblock_flags() >>> >>> 2) Remove the mask parameter >>> >>> 3) Perform the masking in all callers. >> >> get_pfnblock_flags_mask() is also used by get_pageblock_skip() to >> get PB_migrate_skip. I do not think we want to include PB_migrate_skip= >> in the mask to confuse readers. > > The masking will be handled in the caller. > > So get_pageblock_skip() would essentially do a > > return get_pfnblock_flags() & PB_migrate_skip_bit; > > etc. Got it. Sounds good to me. Will do this. > >> >>> >>> >>> >>> Maybe, we should convert set_pfnblock_flags_mask() to >>> >>> void set_clear_pfnblock_flags(struct page *page, unsigned long >>> set_flags, unsigned long clear_flags); >>> >>> And better, splitting it up (or providing helpers) >>> >>> set_pfnblock_flags(struct page *page, unsigned long flags); >>> clear_pfnblock_flags(struct page *page, unsigned long flags); >>> >>> >>> This implies some more code cleanups first that make the code easier = to extend. >>> >> >> The same due to PB_migrate_skip. >> >> Based on your suggestion, we could make {set,get}_pfnblock_flags_mask(= ) >> internal APIs by prepending "__". They are only used by the new >> {get, set, clear}_pfnblock_flags() and {get, set, clear}_pageblock_{sk= ip, isolate}(). >> Then use {get, set, clear}_pfnblock_flags() for all migratetype operat= ions. >> >> WDYT? > > In general, lgtm. I just hope we can avoid the "_mask" part and just ha= ndle it in these functions directly? Sounds good to me. Will put this and "#define NR_PAGEBLOCK_BITS (roundup_pow_of_two(__NR_PAGEBLOCK_BITS))" in a cleanup patch before Patch 1. > >> >>>> + return flags; >>>> } >>>> /** >>>> @@ -402,8 +423,14 @@ void set_pfnblock_flags_mask(struct page *page,= unsigned long flags, >>>> unsigned long bitidx, word_bitidx; >>>> unsigned long word; >>>> +#ifdef CONFIG_MEMORY_ISOLATION >>>> + BUILD_BUG_ON(NR_PAGEBLOCK_BITS !=3D 8); >>>> + /* extra one for MIGRATE_ISOLATE */ >>>> + BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits) + 1); >>>> +#else >>>> BUILD_BUG_ON(NR_PAGEBLOCK_BITS !=3D 4); >>>> BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); >>>> +#endif >>>> bitmap =3D get_pageblock_bitmap(page, pfn); >>>> bitidx =3D pfn_to_bitidx(page, pfn); >>>> @@ -426,6 +453,13 @@ void set_pageblock_migratetype(struct page *pag= e, int migratetype) >>>> migratetype < MIGRATE_PCPTYPES)) >>>> migratetype =3D MIGRATE_UNMOVABLE; >>>> +#ifdef CONFIG_MEMORY_ISOLATION >>>> + if (migratetype =3D=3D MIGRATE_ISOLATE) { >>>> + set_pfnblock_flags_mask(page, PB_migrate_isolate_bit, >>>> + page_to_pfn(page), PB_migrate_isolate_bit); >>>> + return; >>>> + } >>>> +#endif >>>> set_pfnblock_flags_mask(page, (unsigned long)migratetype, >>>> page_to_pfn(page), MIGRATETYPE_MASK); >>>> } >>>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >>>> index b2fc5266e3d2..751e21f6d85e 100644 >>>> --- a/mm/page_isolation.c >>>> +++ b/mm/page_isolation.c >>>> @@ -15,6 +15,17 @@ >>>> #define CREATE_TRACE_POINTS >>>> #include >>>> +static inline bool __maybe_unused get_pageblock_isolate(struct pa= ge *page) >>>> +{ >>>> + return get_pfnblock_flags_mask(page, page_to_pfn(page), >>>> + PB_migrate_isolate_bit); >>>> +} >>>> +static inline void clear_pageblock_isolate(struct page *page) >>>> +{ >>>> + set_pfnblock_flags_mask(page, 0, page_to_pfn(page), >>>> + PB_migrate_isolate_bit); >>>> +} >>> >>> Should these reside in include/linux/pageblock-flags.h, just like the= >>> CONFIG_COMPACTION "skip" variants? >> >> They are only used inside mm/page_isolation.c, so I would leave them >> here until other users come out. > > get_pageblock_skip() and friends are also only used in mm/compaction.c.= > > Having these simple wrapper as inline functions in the same header shou= ld make it consistent. > > ... and avoid tricks like "__maybe_unused" here :) OK, will do this. -- Best Regards, Yan, Zi