Messages in this thread | | | From | Punit Agrawal <> | Subject | Re: [PATCH] mm: compaction: include compound page count for scanning in pageblock isolation | Date | Fri, 15 Jul 2022 10:23:07 +0100 |
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Hi William,
William Lam <william.lam@bytedance.com> writes:
> 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.
A minor suggestion - It maybe useful to include an example trace output to highlight the issue.
> > Signed-off-by: William Lam <william.lam@bytedance.com> > --- > mm/compaction.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 1f89b969c12b..1b51cf2d32b6 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -616,6 +616,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > 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_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > 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_control *cc) > 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);
Regardless of the comment above -
Reviewed-by: Punit Agrawal <punit.agrawal@bytedance.com>
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