+ mm-compaction-consider-the-number-of-scanning-compound-pages-in-isolate-fail-path.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: compaction: consider the number of scanning compound pages in isolate fail path
has been added to the -mm mm-unstable branch.  Its filename is
     mm-compaction-consider-the-number-of-scanning-compound-pages-in-isolate-fail-path.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-consider-the-number-of-scanning-compound-pages-in-isolate-fail-path.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Subject: mm: compaction: consider the number of scanning compound pages in isolate fail path
Date: Thu, 16 Mar 2023 19:06:46 +0800

commit b717d6b93b54 ("mm: compaction: include compound page count for
scanning in pageblock isolation") added compound page statistics for
scanning in pageblock isolation, to make sure the number of scanned pages
is always larger than the number of isolated pages when isolating
mirgratable or free pageblock.

However, when failing to isolate the pages when scanning the migratable or
free pageblocks, the isolation failure path did not consider the scanning
statistics of the compound pages, which result in showing the incorrect
number of scanned pages in tracepoints or in vmstats which will confuse
people about the page scanning pressure in memory compaction.

Thus we should take into account the number of scanning pages when failing
to isolate the compound pages to make the statistics accurate.

Link: https://lkml.kernel.org/r/73d6250a90707649cc010731aedc27f946d722ed.1678962352.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: William Lam <william.lam@bytedance.com>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/compaction.c~mm-compaction-consider-the-number-of-scanning-compound-pages-in-isolate-fail-path
+++ a/mm/compaction.c
@@ -586,6 +586,7 @@ static unsigned long isolate_freepages_b
 			if (likely(order <= MAX_ORDER)) {
 				blockpfn += (1UL << order) - 1;
 				cursor += (1UL << order) - 1;
+				nr_scanned += (1UL << order) - 1;
 			}
 			goto isolate_fail;
 		}
@@ -904,6 +905,7 @@ isolate_migratepages_block(struct compac
 				if (ret == -EBUSY)
 					ret = 0;
 				low_pfn += compound_nr(page) - 1;
+				nr_scanned += compound_nr(page) - 1;
 				goto isolate_fail;
 			}
 
@@ -938,8 +940,10 @@ isolate_migratepages_block(struct compac
 			 * a valid page order. Consider only values in the
 			 * valid order range to prevent low_pfn overflow.
 			 */
-			if (freepage_order > 0 && freepage_order <= MAX_ORDER)
+			if (freepage_order > 0 && freepage_order <= MAX_ORDER) {
 				low_pfn += (1UL << freepage_order) - 1;
+				nr_scanned += (1UL << freepage_order) - 1;
+			}
 			continue;
 		}
 
@@ -954,8 +958,10 @@ isolate_migratepages_block(struct compac
 		if (PageCompound(page) && !cc->alloc_contig) {
 			const unsigned int order = compound_order(page);
 
-			if (likely(order <= MAX_ORDER))
+			if (likely(order <= MAX_ORDER)) {
 				low_pfn += (1UL << order) - 1;
+				nr_scanned += (1UL << order) - 1;
+			}
 			goto isolate_fail;
 		}
 
@@ -1077,6 +1083,7 @@ isolate_migratepages_block(struct compac
 			 */
 			if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
 				low_pfn += compound_nr(page) - 1;
+				nr_scanned += compound_nr(page) - 1;
 				SetPageLRU(page);
 				goto isolate_fail_put;
 			}
_

Patches currently in -mm which might be from baolin.wang@linux.alibaba.com are

mm-compaction-consider-the-number-of-scanning-compound-pages-in-isolate-fail-path.patch
mm-compaction-fix-the-possible-deadlock-when-isolating-hugetlb-pages.patch