From 511a69b27fe6c2d7312789bd9e2e40b00e3903ef Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Fri, 19 May 2023 14:39:56 +0200 Subject: mm: compaction: simplify should_compact_retry() 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. [hannes@cmpxchg.org: restore behavior when hitting max_retries] Link: https://lkml.kernel.org/r/20230602144705.GB161817@cmpxchg.org Link: https://lkml.kernel.org/r/20230519123959.77335-3-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Vlastimil Babka Cc: Mel Gorman Cc: Michal Hocko Signed-off-by: Andrew Morton --- mm/page_alloc.c | 57 +++++++++++++++++++-------------------------------------- 1 file changed, 19 insertions(+), 38 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e3a3ebc2dfce..7e8673504a3d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3469,21 +3469,6 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, if (fatal_signal_pending(current)) return false; - /* - * 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)++; - - /* - * 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; - /* * Compaction was skipped due to a lack of free order-0 * migration targets. Continue if reclaim can help. @@ -3494,35 +3479,31 @@ 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. + * Compaction managed to coalesce some page blocks, but the + * allocation failed presumably due to a race. Retry some. */ - if (compact_result == COMPACT_DEFERRED || - compact_result == COMPACT_CONTENDED || - compact_result == COMPACT_PARTIAL_SKIPPED) - goto check_priority; + 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; - /* - * !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; + 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; -- cgit v1.2.3