PGPool::update: avoid expensive union_of

Achieve the same result using a swap (constant complexity), and an assignment (linear complexity). Signed-off-by: Zac Medico <zmedico@gmail.com>
zmedico · Aug 24, 2017 · bf20b66 · bf20b66
1 parent 457c145
commit bf20b66
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/src/osd/PG.cc b/src/osd/PG.cc
@@ -241,8 +241,9 @@ void PGPool::update(OSDMapRef map)
     interval_set<snapid_t> intersection;
     intersection.intersection_of(newly_removed_snaps, cached_removed_snaps);
     if (intersection == cached_removed_snaps) {
-        newly_removed_snaps.subtract(cached_removed_snaps);
-        cached_removed_snaps.union_of(newly_removed_snaps);
+        cached_removed_snaps.swap(newly_removed_snaps);
+        newly_removed_snaps = cached_removed_snaps;
+        newly_removed_snaps.subtract(intersection);
     } else {
         lgeneric_subdout(cct, osd, 0) << __func__
           << " cached_removed_snaps shrank from " << cached_removed_snaps