The rescan field was not well named albeit accurate at the time. Rename the
field to finish_pageblock to indicate that the remainder of the pageblock
should be scanned regardless of COMPACT_CLUSTER_MAX. The intent is that
pageblocks with transient failures get marked for skipping to avoid
revisiting the same pageblock.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 24 ++++++++++++------------
mm/internal.h | 6 +++++-
2 files changed, 17 insertions(+), 13 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index ca1603524bbe..c018b0e65720 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1102,12 +1102,12 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
/*
* Avoid isolating too much unless this block is being
- * rescanned (e.g. dirty/writeback pages, parallel allocation)
+ * fully scanned (e.g. dirty/writeback pages, parallel allocation)
* or a lock is contended. For contention, isolate quickly to
* potentially remove one source of contention.
*/
if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX &&
- !cc->rescan && !cc->contended) {
+ !cc->finish_pageblock && !cc->contended) {
++low_pfn;
break;
}
@@ -1172,14 +1172,14 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
/*
- * Updated the cached scanner pfn once the pageblock has been scanned
+ * Update 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 || cc->rescan)) {
+ if (low_pfn == end_pfn && (!nr_isolated || cc->finish_pageblock)) {
if (valid_page && !skip_updated)
set_pageblock_skip(valid_page);
update_cached_migrate(cc, low_pfn);
@@ -2374,17 +2374,17 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
unsigned long iteration_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.
+ * Avoid multiple rescans of the same pageblock 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;
+ cc->finish_pageblock = false;
if (pageblock_start_pfn(last_migrated_pfn) ==
pageblock_start_pfn(iteration_start_pfn)) {
- cc->rescan = true;
+ cc->finish_pageblock = true;
}
switch (isolate_migratepages(cc)) {
diff --git a/mm/internal.h b/mm/internal.h
index bcf75a8b032d..21466d0ab22f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -422,7 +422,11 @@ struct compact_control {
bool proactive_compaction; /* kcompactd proactive compaction */
bool whole_zone; /* Whole zone should/has been scanned */
bool contended; /* Signal lock contention */
- bool rescan; /* Rescanning the same pageblock */
+ bool finish_pageblock; /* Scan the remainder of a pageblock. Used
+ * when there are potentially transient
+ * isolation or migration failures to
+ * ensure forward progress.
+ */
bool alloc_contig; /* alloc_contig_range allocation */
};
--
2.35.3
