On 11.02.21 01:56, Mike Kravetz wrote:
On 2/8/21 2:38 AM, 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@xxxxxxx>
---
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)) {
Thanks for doing this!
I agree with everything in the discussion you and David had. This code
is racy, but since we are scanning lockless there is no way to eliminate
them all. Best to just minimize the windows and document.
Agreed - and make sure that we don't have strange side. (e.g., in the
next patch, allocate a new page, try to dissolve. Dissolving fails, what
happens to the just-allocated page?)
--
Thanks,
David / dhildenb
