The different branches for retry are unnecessarily complicated. There
are really only three outcomes: progress (retry n times), skipped
(retry if reclaim can help), failed (retry with higher priority).
Rearrange the branches and the retry counter to make it simpler.
v2:
- fix trace point build (Mel)
- fix max_retries logic for costly allocs (Huang)
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
mm/page_alloc.c | 53 +++++++++++++++----------------------------------
1 file changed, 16 insertions(+), 37 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5a84a0bebc37..72660e924b95 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3772,16 +3772,22 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
* Compaction managed to coalesce some page blocks, but the
* allocation failed presumably due to a race. Retry some.
*/
- if (compact_result == COMPACT_SUCCESS)
- (*compaction_retries)++;
+ if (compact_result == COMPACT_SUCCESS) {
+ /*
+ * !costly requests are much more important than
+ * __GFP_RETRY_MAYFAIL costly ones because they are de
+ * facto nofail and invoke OOM killer to move on while
+ * costly can fail and users are ready to cope with
+ * that. 1/4 retries is rather arbitrary but we would
+ * need much more detailed feedback from compaction to
+ * make a better decision.
+ */
+ if (order > PAGE_ALLOC_COSTLY_ORDER)
+ max_retries /= 4;
- /*
- * All zones were scanned completely and still no result. It
- * doesn't really make much sense to retry except when the
- * failure could be caused by insufficient priority
- */
- if (compact_result == COMPACT_COMPLETE)
- goto check_priority;
+ ret = ++(*compaction_retries) <= max_retries;
+ goto out;
+ }
/*
* Compaction was skipped due to a lack of free order-0
@@ -3793,35 +3799,8 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
}
/*
- * If compaction backed due to being deferred, due to
- * contended locks in async mode, or due to scanners meeting
- * after a partial scan, retry with increased priority.
- */
- if (compact_result == COMPACT_DEFERRED ||
- compact_result == COMPACT_CONTENDED ||
- compact_result == COMPACT_PARTIAL_SKIPPED)
- goto check_priority;
-
- /*
- * !costly requests are much more important than __GFP_RETRY_MAYFAIL
- * costly ones because they are de facto nofail and invoke OOM
- * killer to move on while costly can fail and users are ready
- * to cope with that. 1/4 retries is rather arbitrary but we
- * would need much more detailed feedback from compaction to
- * make a better decision.
- */
- if (order > PAGE_ALLOC_COSTLY_ORDER)
- max_retries /= 4;
- if (*compaction_retries <= max_retries) {
- ret = true;
- goto out;
- }
-
- /*
- * Make sure there are attempts at the highest priority if we exhausted
- * all retries or failed at the lower priorities.
+ * Compaction failed. Retry with increasing priority.
*/
-check_priority:
min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
--
2.40.0
