Messages in this thread | | | Date | Mon, 12 Feb 2024 10:13:56 +0100 | Subject | Re: [PATCH 1/2] mm: compaction: limit the suitable target page order to be less than cc->order | From | Vlastimil Babka <> |
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On 1/22/24 14:01, Baolin Wang wrote: > It can not improve the fragmentation if we isolate the target free pages > exceeding cc->order, especially when the cc->order is less than pageblock_order. > For example, suppose the pageblock_order is MAX_ORDER (size is 4M) and cc->order > is 2M THP size, we should not isolate other 2M free pages to be the migration > target, which can not improve the fragmentation. > > Moreover this is also applicable for large folio compaction.
So why not Cc: Zi Yan? (done)
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
I doubt this will make much difference, because if such a larger order free page exists, we shouldn't have a reason to be compacting for a lower order in the first place?
> --- > mm/compaction.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 27ada42924d5..066b72b3471a 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1346,12 +1346,14 @@ static bool suitable_migration_target(struct compact_control *cc, > { > /* If the page is a large free page, then disallow migration */ > if (PageBuddy(page)) { > + int order = cc->order > 0 ? cc->order : pageblock_order; > + > /* > * We are checking page_order without zone->lock taken. But > * the only small danger is that we skip a potentially suitable > * pageblock, so it's not worth to check order for valid range. > */ > - if (buddy_order_unsafe(page) >= pageblock_order) > + if (buddy_order_unsafe(page) >= order) > return false; > } >
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