Messages in this thread | | | From | David Hildenbrand <> | Subject | Re: [RFC PATCH 1/2] mm,page_alloc: Make alloc_contig_range handle in-use hugetlb pages | Date | Wed, 10 Feb 2021 09:56:37 +0100 |
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On 08.02.21 11:38, Oscar Salvador wrote: > alloc_contig_range is not prepared to handle hugetlb pages and will > fail if it ever sees one, but since they can be migrated as any other > page (LRU and Movable), it makes sense to also handle them. > > For now, do it only when coming from alloc_contig_range. > > Signed-off-by: Oscar Salvador <osalvador@suse.de> > --- > mm/compaction.c | 17 +++++++++++++++++ > mm/vmscan.c | 5 +++-- > 2 files changed, 20 insertions(+), 2 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index e5acb9714436..89cd2e60da29 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -940,6 +940,22 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > goto isolate_fail; > } > > + /* > + * Handle hugetlb pages only when coming from alloc_contig > + */ > + if (PageHuge(page) && cc->alloc_contig) { > + if (page_count(page)) {
I wonder if we should care about races here. What if someone concurrently allocates/frees?
Note that PageHuge() succeeds on tail pages, isolate_huge_page() not, i assume we'll have to handle that as well.
I wonder if it would make sense to move some of the magic to hugetlb code and handle it there with less chances for races (isolate if used, alloc-and-dissolve if not).
> + /* > + * Hugetlb page in-use. Isolate and migrate. > + */ > + if (isolate_huge_page(page, &cc->migratepages)) { > + low_pfn += compound_nr(page) - 1; > + goto isolate_success_no_list; > + } > + }
-- Thanks,
David / dhildenb
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