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-rw-r--r--mm/compaction.c47
1 files changed, 27 insertions, 20 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 0dce7e87d771..1ccb015ab1eb 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -680,6 +680,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
/* Time to isolate some pages for migration */
for (; low_pfn < end_pfn; low_pfn++) {
+ bool is_lru;
+
/*
* Periodically drop the lock (if held) regardless of its
* contention, to give chance to IRQs. Abort async compaction
@@ -723,36 +725,35 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* It's possible to migrate LRU pages and balloon pages
* Skip any other type of page
*/
- if (!PageLRU(page)) {
+ is_lru = PageLRU(page);
+ if (!is_lru) {
if (unlikely(balloon_page_movable(page))) {
if (balloon_page_isolate(page)) {
/* Successfully isolated */
goto isolate_success;
}
}
- continue;
}
/*
- * PageLRU is set. lru_lock normally excludes isolation
- * splitting and collapsing (collapsing has already happened
- * if PageLRU is set) but the lock is not necessarily taken
- * here and it is wasteful to take it just to check transhuge.
- * Check TransHuge without lock and skip the whole pageblock if
- * it's either a transhuge or hugetlbfs page, as calling
- * compound_order() without preventing THP from splitting the
- * page underneath us may return surprising results.
+ * Regardless of being on LRU, compound pages such as THP and
+ * hugetlbfs are not to be compacted. We can potentially save
+ * a lot of iterations if we skip them at once. The check is
+ * racy, but we can consider only valid values and the only
+ * danger is skipping too much.
*/
- if (PageTransHuge(page)) {
- if (!locked)
- low_pfn = ALIGN(low_pfn + 1,
- pageblock_nr_pages) - 1;
- else
- low_pfn += (1 << compound_order(page)) - 1;
+ if (PageCompound(page)) {
+ unsigned int comp_order = compound_order(page);
+
+ if (likely(comp_order < MAX_ORDER))
+ low_pfn += (1UL << comp_order) - 1;
continue;
}
+ if (!is_lru)
+ continue;
+
/*
* Migration will fail if an anonymous page is pinned in memory,
* so avoid taking lru_lock and isolating it unnecessarily in an
@@ -769,11 +770,17 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (!locked)
break;
- /* Recheck PageLRU and PageTransHuge under lock */
+ /* Recheck PageLRU and PageCompound under lock */
if (!PageLRU(page))
continue;
- if (PageTransHuge(page)) {
- low_pfn += (1 << compound_order(page)) - 1;
+
+ /*
+ * Page become compound since the non-locked check,
+ * and it's on LRU. It can only be a THP so the order
+ * is safe to read and it's 0 for tail pages.
+ */
+ if (unlikely(PageCompound(page))) {
+ low_pfn += (1UL << compound_order(page)) - 1;
continue;
}
}
@@ -784,7 +791,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (__isolate_lru_page(page, isolate_mode) != 0)
continue;
- VM_BUG_ON_PAGE(PageTransCompound(page), page);
+ VM_BUG_ON_PAGE(PageCompound(page), page);
/* Successfully isolated */
del_page_from_lru_list(page, lruvec, page_lru(page));