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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: CCF4B20018 X-Rspam-User: X-Stat-Signature: pq1ojj3nydpb3w6b834h7jkcsi4i43qi X-Rspamd-Server: rspam01 X-HE-Tag: 1690861478-133835 X-HE-Meta: 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 nqqnArnD K/xX2zaO0bsOv5KVkfX0CnSyGaLTQuFXnrdS4Vd/oNE5SEzymHJKTVlTusI4SlOVCGF6qECUrRkBTULn8+vq6RAffepEo69Z4FNRt8HPCLGzVk9bTxY0pH5g41qOhkj6FqzXmIQB7kr6WXad/iO9kle/JbZE/xKWSrNr7o9F+9BgKacCpy7oAIwbth/YvT9R8r9jaA6OFKtSITwrzHqWs3mk7svXbnjjfy23Fk7kUnmX9V4kL3CmHXz/cpIlzKFFZCb5onzzbemRJ8ttIZTwWQBLfGx3YDVcF4ozeQdc6nDOz5Fo= 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 8/1/2023 11:24 AM, Kemeng Shi wrote: > > > on 8/1/2023 10:42 AM, Baolin Wang wrote: >> >> >> On 7/29/2023 1:10 AM, Kemeng Shi wrote: >>> In old code, we set skip to found page block in fast_find_migrateblock. So >>> we use fast_find_block to avoid skip found page block from >>> fast_find_migrateblock. >>> In 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in >>> fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock, >>> then fast_find_block is useless. >>> >>> Signed-off-by: Kemeng Shi >>> --- >>>   mm/compaction.c | 12 +----------- >>>   1 file changed, 1 insertion(+), 11 deletions(-) >>> >>> diff --git a/mm/compaction.c b/mm/compaction.c >>> index ad535f880c70..09c36251c613 100644 >>> --- a/mm/compaction.c >>> +++ b/mm/compaction.c >>> @@ -1949,7 +1949,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>       const isolate_mode_t isolate_mode = >>>           (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | >>>           (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); >>> -    bool fast_find_block; >>>         /* >>>        * Start at where we last stopped, or beginning of the zone as >>> @@ -1961,13 +1960,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>       if (block_start_pfn < cc->zone->zone_start_pfn) >>>           block_start_pfn = cc->zone->zone_start_pfn; >>>   -    /* >>> -     * fast_find_migrateblock marks a pageblock skipped so to avoid >>> -     * the isolation_suitable check below, check whether the fast >>> -     * search was successful. >>> -     */ >>> -    fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; >>> - >>>       /* Only scan within a pageblock boundary */ >>>       block_end_pfn = pageblock_end_pfn(low_pfn); >>>   @@ -1976,7 +1968,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>        * Do not cross the free scanner. >>>        */ >>>       for (; block_end_pfn <= cc->free_pfn; >>> -            fast_find_block = false, >>>               cc->migrate_pfn = low_pfn = block_end_pfn, >>>               block_start_pfn = block_end_pfn, >>>               block_end_pfn += pageblock_nr_pages) { >>> @@ -2007,8 +1998,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >>>            * before making it "skip" so other compaction instances do >>>            * not scan the same block. >>>            */ >>> -        if (pageblock_aligned(low_pfn) && >>> -            !fast_find_block && !isolation_suitable(cc, page)) >>> +        if (pageblock_aligned(low_pfn) && !isolation_suitable(cc, page)) >> >> I do not think so. If the pageblock is found by fast_find_migrateblock(), that means it definitely has not been set the skip flag, so there is not need to call isolation_suitable() if fast_find_block is true, right? >> >> > Actually, found pageblock could be set skip as: > 1. other compactor could mark this pageblock as skip after zone lock is realeased > in fast_find_migrateblock. Yes, but your patch also can not close this race window, that means it can also be set skip flag after the isolation_suitable() validation by other compactors. > 2. fast_find_migrateblock may uses pfn from reinit_migrate_pfn which is previously found > and sacnned. It could be fully sacnned and marked skip after it's first return from Right, but now the 'fast_find_block' is false, and we will call isolation_suitable() to validate the skip flag. > fast_find_migrateblock and it should be skipped. > Thanks!