mm, compaction: determine isolation mode only once

The conditions that control the isolation mode in
isolate_migratepages_range() do not change during the iteration, so
extract them out and only define the value once.

This actually does have an effect, gcc doesn't optimize it itself because
of cc->sync.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/compaction.c b/mm/compaction.c
index 054c28b51c7559fdd831d1bb3f3c8e82a028e3a4..37f976287068cef4ed185836059da2cc12cdceda 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -460,12 +460,13 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
        unsigned long last_pageblock_nr = 0, pageblock_nr;
        unsigned long nr_scanned = 0, nr_isolated = 0;
        struct list_head *migratelist = &cc->migratepages;
-       isolate_mode_t mode = 0;
        struct lruvec *lruvec;
        unsigned long flags;
        bool locked = false;
        struct page *page = NULL, *valid_page = NULL;
        bool skipped_async_unsuitable = false;
+       const isolate_mode_t mode = (!cc->sync ? ISOLATE_ASYNC_MIGRATE : 0) |
+                                   (unevictable ? ISOLATE_UNEVICTABLE : 0);
 
        /*
         * Ensure that there are not too many pages isolated from the LRU
@@ -608,12 +609,6 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
                        continue;
                }
 
-               if (!cc->sync)
-                       mode |= ISOLATE_ASYNC_MIGRATE;
-
-               if (unevictable)
-                       mode |= ISOLATE_UNEVICTABLE;
-
                lruvec = mem_cgroup_page_lruvec(page, zone);
 
                /* Try isolate the page */