The patch titled
Subject: mm: compaction: simplify should_compact_retry()
has been added to the -mm mm-unstable branch. Its filename is
mm-compaction-simplify-should_compact_retry.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-simplify-should_compact_retry.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: compaction: simplify should_compact_retry()
Date: Fri, 19 May 2023 14:39:56 +0200
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.
Link: https://lkml.kernel.org/r/20230519123959.77335-3-hannes@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 53 +++++++++++++---------------------------------
1 file changed, 16 insertions(+), 37 deletions(-)
--- a/mm/page_alloc.c~mm-compaction-simplify-should_compact_retry
+++ a/mm/page_alloc.c
@@ -3510,16 +3510,22 @@ should_compact_retry(struct alloc_contex
* 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
@@ -3531,35 +3537,8 @@ should_compact_retry(struct alloc_contex
}
/*
- * 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;
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
mm-compaction-remove-compaction-result-helpers.patch
mm-compaction-simplify-should_compact_retry.patch
mm-compaction-refactor-__compaction_suitable.patch
mm-compaction-remove-unnecessary-is_via_compact_memory-checks.patch
mm-compaction-drop-redundant-watermark-check-in-compaction_zonelist_suitable.patch
