The patch titled
Subject: mm: compaction: include compound page count for scanning in pageblock isolation
has been added to the -mm mm-unstable branch. Its filename is
mm-compaction-include-compound-page-count-for-scanning-in-pageblock-isolation.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-include-compound-page-count-for-scanning-in-pageblock-isolation.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: William Lam <william.lam@xxxxxxxxxxxxx>
Subject: mm: compaction: include compound page count for scanning in pageblock isolation
Date: Mon, 11 Jul 2022 21:28:06 +0100
The number of scanned pages can be lower than the number of isolated pages
when isolating mirgratable or free pageblock. The metric is being
reported in trace event and also used in vmstat.
This behaviour is confusing since currently the count for isolated pages
takes account of compound page but not for the case of scanned pages. And
given that the number of isolated pages(nr_taken) reported in
mm_compaction_isolate_template trace event is on a single-page basis, the
ambiguity when reporting the number of scanned pages can be removed by
also including compound page count.
Link: https://lkml.kernel.org/r/20220711202806.22296-1-william.lam@xxxxxxxxxxxxx
Signed-off-by: William Lam <william.lam@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/compaction.c~mm-compaction-include-compound-page-count-for-scanning-in-pageblock-isolation
+++ a/mm/compaction.c
@@ -616,6 +616,7 @@ static unsigned long isolate_freepages_b
break;
set_page_private(page, order);
+ nr_scanned += isolated - 1;
total_isolated += isolated;
cc->nr_freepages += isolated;
list_add_tail(&page->lru, freelist);
@@ -1101,6 +1102,7 @@ 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
@@ -1504,6 +1506,7 @@ fast_isolate_freepages(struct compact_co
if (__isolate_free_page(page, order)) {
set_page_private(page, order);
nr_isolated = 1 << order;
+ nr_scanned += nr_isolated - 1;
cc->nr_freepages += nr_isolated;
list_add_tail(&page->lru, &cc->freepages);
count_compact_events(COMPACTISOLATED, nr_isolated);
_
Patches currently in -mm which might be from william.lam@xxxxxxxxxxxxx are
mm-compaction-include-compound-page-count-for-scanning-in-pageblock-isolation.patch
