From: Zac Medico <zmedico@gmail.com>
Date: Thu, 24 Aug 2017 16:40:45 +0000 (-0700)
Subject: PGPool::update: avoid expensive union_of
X-Git-Tag: v13.0.1~1141^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=bf20b661cb6a6a33d9e93fb44ad1470f9f8245d2;p=ceph.git

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>
---

diff --git a/src/osd/PG.cc b/src/osd/PG.cc
index 3f51b1eb2631..3e671de9b092 100644
--- 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