Re: [PATCH v2] mm/compaction: fix set skip in fast_find_migrateblock

[Miaohe Lin <linmiaohe@huawei.com>]

On 2022/7/12 15:27, Zhou Chuyi wrote:
> From: zhouchuyi <zhouchuyi@bytedance.com>
> 
> 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%*
> 
> Fixs: 'commit 70b44595eafe9 ("mm, compaction: use free lists
> to quickly locate a migration source")'

Thanks for your patch. Yet something to improve:

./scripts/checkpatch.pl v2-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
ERROR: Please use git commit description style 'commit <12+ chars of sha1> ("<title line>")' - ie: 'commit 70b44595eafe ("mm, compaction: use free lists to quickly locate a migration source")'
#101:
Fixs: 'commit 70b44595eafe9 ("mm, compaction: use free lists
to quickly locate a migration source")'

total: 1 errors, 0 warnings, 7 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

[PATCH v2] mm_compaction  fix set skip in fast_find_migrateblock.eml has style problems, please review.

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.

And remember runing get_maintainer.pl to get the right people before sending the patch:

./scripts/get_maintainer.pl v2-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
Andrew Morton <akpm@linux-foundation.org> (maintainer:MEMORY MANAGEMENT)
linux-mm@kvack.org (open list:MEMORY MANAGEMENT)
linux-kernel@vger.kernel.org (open list)

BTW: It's not enforced but ~70 chars per line in commit log might be preferred.

> 
> Signed-off-by: zhouchuyi <zhouchuyi@bytedance.com>

Thanks.

> ---
>  mm/compaction.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 1f89b969c..a1a2b50c8 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1852,7 +1852,6 @@ 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;
>  			}
>  		}
>