Re: [PATCH v3] mm/compaction: fix set skip in fast_find_migrateblock

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(cc Mel)

On Wed, 13 Jul 2022 14:20:09 +0800 Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> wrote:

> From: zhouchuyi <zhouchuyi@xxxxxxxxxxxxx>
> 
> When we successfully find a pageblock in fast_find_migrateblock(),
> the block will be set skip-flag through set_pageblock_skip(). However,
> when entering isolate_migratepages_block(), the whole pageblock will
> be skipped due to the branch
> 'if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages))'.
> Eventually we will goto isolate_abort and isolate nothing. That cause
> fast_find_migrateblock useless.
> 
> In this Patch, when we find a suitable pageblock in fast_find_
> migrateblock, we do noting but let isolate_migratepages_block
> to set skip flag to the pageblock after scan it. Normally,
> we would isolate some pages from the fast-find block.
> 
> I use mmtest/thpscale-madvhugepage test it. Here is the result:
>                             baseline               patch
> Amean     fault-both-1      1331.66 (   0.00%)     1261.04 *   5.30%*
> Amean     fault-both-3      1383.95 (   0.00%)     1191.69 *  13.89%*
> Amean     fault-both-5      1568.13 (   0.00%)     1445.20 *   7.84%*
> Amean     fault-both-7      1819.62 (   0.00%)     1555.13 *  14.54%*
> Amean     fault-both-12     1106.96 (   0.00%)     1149.43 *  -3.84%*
> Amean     fault-both-18     2196.93 (   0.00%)     1875.77 *  14.62%*
> Amean     fault-both-24     2642.69 (   0.00%)     2671.21 *  -1.08%*
> Amean     fault-both-30     2901.89 (   0.00%)     2857.32 *   1.54%*
> Amean     fault-both-32     3747.00 (   0.00%)     3479.23 *   7.15%*
> 
> Fixes: 70b44595eafe9 ("mm, compaction: use free lists to quickly locate a migration source")
> 
> Signed-off-by: zhouchuyi <zhouchuyi@xxxxxxxxxxxxx>
> ---
>  mm/compaction.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 962d05d1e187..abc7b0834471 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1850,7 +1850,6 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
>  					pfn = cc->zone->zone_start_pfn;
>  				cc->fast_search_fail = 0;
>  				found_block = true;
> -				set_pageblock_skip(freepage);
>  				break;
>  			}
>  		}
> -- 
> 2.20.1
> 




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