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SubjectRe: [PATCH 4/8] mm/compaction: remove stale fast_find_block flag in isolate_migratepages
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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 <shikemeng@huaweicloud.com>
> ---
> 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?

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