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

* + mm-compaction-consider-the-number-of-scanning-compound-pages-in-isolate-fail-path.patch added to mm-unstable branch
@ 2023-03-13 19:31 Andrew Morton
  0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2023-03-13 19:31 UTC (permalink / raw)
  To: mm-commits, william.lam, vbabka, osalvador, mike.kravetz,
	mgorman, baolin.wang, akpm


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: Mon, 13 Mar 2023 18:37:16 +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
migratable or free pageblocks.

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 can show the incorrect number of
scanned pages in tracepoints or vmstats to make people confused about the
page scanning pressure in memory compaction.

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

Link: https://lkml.kernel.org/r/1bc1c955b03603c4e14f56dfbbef9f637f18dbbd.1678703534.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: William Lam <william.lam@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.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
@@ -587,6 +587,7 @@ static unsigned long isolate_freepages_b
 				blockpfn += (1UL << order) - 1;
 				cursor += (1UL << order) - 1;
 			}
+			nr_scanned += (1UL << order) - 1;
 			goto isolate_fail;
 		}
 
@@ -873,9 +874,8 @@ isolate_migratepages_block(struct compac
 			cond_resched();
 		}
 
-		nr_scanned++;
-
 		page = pfn_to_page(low_pfn);
+		nr_scanned += compound_nr(page);
 
 		/*
 		 * Check if the pageblock has already been marked skipped.
@@ -1077,6 +1077,7 @@ 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;
 			}
@@ -1097,7 +1098,6 @@ isolate_success:
 isolate_success_no_list:
 		cc->nr_migratepages += compound_nr(page);
 		nr_isolated += compound_nr(page);
-		nr_scanned += compound_nr(page) - 1;
 
 		/*
 		 * Avoid isolating too much unless this block is being
_

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


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