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-rw-r--r--mm/compaction.c32
-rw-r--r--mm/internal.h1
2 files changed, 27 insertions, 6 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 6d42ea126242..00a5126b6548 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -949,8 +949,11 @@ isolate_success:
cc->nr_migratepages++;
nr_isolated++;
- /* Avoid isolating too much */
- if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
+ /*
+ * Avoid isolating too much unless this block is being
+ * rescanned (e.g. dirty/writeback pages, parallel allocation).
+ */
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX && !cc->rescan) {
++low_pfn;
break;
}
@@ -997,11 +1000,14 @@ isolate_abort:
spin_unlock_irqrestore(zone_lru_lock(zone), flags);
/*
- * Updated the cached scanner pfn if the pageblock was scanned
- * without isolating a page. The pageblock may not be marked
- * skipped already if there were no LRU pages in the block.
+ * Updated the cached scanner pfn once the pageblock has been scanned
+ * Pages will either be migrated in which case there is no point
+ * scanning in the near future or migration failed in which case the
+ * failure reason may persist. The block is marked for skipping if
+ * there were no pages isolated in the block or if the block is
+ * rescanned twice in a row.
*/
- if (low_pfn == end_pfn && !nr_isolated) {
+ if (low_pfn == end_pfn && (!nr_isolated || cc->rescan)) {
if (valid_page && !skip_updated)
set_pageblock_skip(valid_page);
update_cached_migrate(cc, low_pfn);
@@ -2035,6 +2041,20 @@ static enum compact_result compact_zone(struct compact_control *cc)
int err;
unsigned long start_pfn = cc->migrate_pfn;
+ /*
+ * Avoid multiple rescans which can happen if a page cannot be
+ * isolated (dirty/writeback in async mode) or if the migrated
+ * pages are being allocated before the pageblock is cleared.
+ * The first rescan will capture the entire pageblock for
+ * migration. If it fails, it'll be marked skip and scanning
+ * will proceed as normal.
+ */
+ cc->rescan = false;
+ if (pageblock_start_pfn(last_migrated_pfn) ==
+ pageblock_start_pfn(start_pfn)) {
+ cc->rescan = true;
+ }
+
switch (isolate_migratepages(cc->zone, cc)) {
case ISOLATE_ABORT:
ret = COMPACT_CONTENDED;
diff --git a/mm/internal.h b/mm/internal.h
index 983cb975545f..d5b999e5eb5f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -205,6 +205,7 @@ struct compact_control {
bool direct_compaction; /* False from kcompactd or /proc/... */
bool whole_zone; /* Whole zone should/has been scanned */
bool contended; /* Signal lock or sched contention */
+ bool rescan; /* Rescanning the same pageblock */
};
unsigned long