[RFC PATCH 13/26] mm: compaction: remove compaction result helpers

Johannes Weiner
2023-04-18T19:15:08Z

I found myself repeatedly looking up the implementation of these
helpers while working on the code, which suggests they are not a
helpful abstraction. Inline them.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/compaction.h | 92 ----------------------------------
include/trace/events/mmflags.h | 4 +-
mm/page_alloc.c | 30 ++++++-----
3 files changed, 19 insertions(+), 107 deletions(-)

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 06eeb2e25833..7635e220215a 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -103,78 +103,6 @@ extern enum compact_result compaction_suitable(struct zone *zone, int order,
extern void compaction_defer_reset(struct zone *zone, int order,
bool alloc_success);

-/* Compaction has made some progress and retrying makes sense */
-static inline bool compaction_made_progress(enum compact_result result)
-{
- /*
- * Even though this might sound confusing this in fact tells us
- * that the compaction successfully isolated and migrated some
- * pageblocks.
- */
- if (result == COMPACT_SUCCESS)
- return true;
-
- return false;
-}
-
-/* Compaction has failed and it doesn't make much sense to keep retrying. */
-static inline bool compaction_failed(enum compact_result result)
-{
- /* All zones were scanned completely and still not result. */
- if (result == COMPACT_COMPLETE)
- return true;
-
- return false;
-}
-
-/* Compaction needs reclaim to be performed first, so it can continue. */
-static inline bool compaction_needs_reclaim(enum compact_result result)
-{
- /*
- * Compaction backed off due to watermark checks for order-0
- * so the regular reclaim has to try harder and reclaim something.
- */
- if (result == COMPACT_SKIPPED)
- return true;
-
- return false;
-}
-
-/*
- * Compaction has backed off for some reason after doing some work or none
- * at all. It might be throttling or lock contention. Retrying might be still
- * worthwhile, but with a higher priority if allowed.
- */
-static inline bool compaction_withdrawn(enum compact_result result)
-{
- /*
- * If compaction is deferred for high-order allocations, it is
- * because sync compaction recently failed. If this is the case
- * and the caller requested a THP allocation, we do not want
- * to heavily disrupt the system, so we fail the allocation
- * instead of entering direct reclaim.
- */
- if (result == COMPACT_DEFERRED)
- return true;
-
- /*
- * If compaction in async mode encounters contention or blocks higher
- * priority task we back off early rather than cause stalls.
- */
- if (result == COMPACT_CONTENDED)
- return true;
-
- /*
- * Page scanners have met but we haven't scanned full zones so this
- * is a back off in fact.
- */
- if (result == COMPACT_PARTIAL_SKIPPED)
- return true;
-
- return false;
-}
-
-
bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
int alloc_flags);

@@ -193,26 +121,6 @@ static inline enum compact_result compaction_suitable(struct zone *zone, int ord
return COMPACT_SKIPPED;
}

-static inline bool compaction_made_progress(enum compact_result result)
-{
- return false;
-}
-
-static inline bool compaction_failed(enum compact_result result)
-{
- return false;
-}
-
-static inline bool compaction_needs_reclaim(enum compact_result result)
-{
- return false;
-}
-
-static inline bool compaction_withdrawn(enum compact_result result)
-{
- return true;
-}
-
static inline void kcompactd_run(int nid)
{
}
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 412b5a46374c..47bfeca4cf02 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -222,8 +222,8 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
#define compact_result_to_feedback(result) \
({ \
enum compact_result __result = result; \
- (compaction_failed(__result)) ? COMPACTION_FAILED : \
- (compaction_withdrawn(__result)) ? COMPACTION_WITHDRAWN : COMPACTION_PROGRESS; \
+ (__result == COMPACT_COMPLETE) ? COMPACTION_FAILED : \
+ (__result == COMPACT_SUCCESS) ? COMPACTION_PROGRESS : COMPACTION_WITHDRAWN; \
})

#define COMPACTION_FEEDBACK \
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5f2a0037bed1..c3b7dc479936 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4620,35 +4620,39 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
if (fatal_signal_pending(current))
return false;

- if (compaction_made_progress(compact_result))
+ /*
+ * 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)++;

/*
- * compaction considers all the zone as desperately out of memory
- * so it doesn't really make much sense to retry except when the
+ * 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 (compaction_failed(compact_result))
+ if (compact_result == COMPACT_COMPLETE)
goto check_priority;

/*
- * compaction was skipped because there are not enough order-0 pages
- * to work with, so we retry only if it looks like reclaim can help.
+ * Compaction was skipped due to a lack of free order-0
+ * migration targets. Continue if reclaim can help.
*/
- if (compaction_needs_reclaim(compact_result)) {
+ if (compact_result == COMPACT_SKIPPED) {
ret = compaction_zonelist_suitable(ac, order, alloc_flags);
goto out;
}

/*
- * make sure the compaction wasn't deferred or didn't bail out early
- * due to locks contention before we declare that we should give up.
- * But the next retry should use a higher priority if allowed, so
- * we don't just keep bailing out endlessly.
+ * 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 (compaction_withdrawn(compact_result)) {
+ 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
--
2.39.2