From 3102b0a5b4cd63acccac78ca541b73fe28b4faa6 Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Tue, 24 Dec 2013 21:19:25 +0200 Subject: [PATCH] crush: add note about r in recursive choose Reflects ceph.git commit 4551fee9ad89d0427ed865d766d0d44004d3e3e1. Signed-off-by: Ilya Dryomov Reviewed-by: Sage Weil --- net/ceph/crush/mapper.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c index caeb1066bea3..77b7a73e65cf 100644 --- a/net/ceph/crush/mapper.c +++ b/net/ceph/crush/mapper.c @@ -514,6 +514,14 @@ static void crush_choose_indep(const struct crush_map *map, /* choose through intervening buckets */ for (;;) { + /* note: we base the choice on the position + * even in the nested call. that means that + * if the first layer chooses the same bucket + * in a different position, we will tend to + * choose a different item in that bucket. + * this will involve more devices in data + * movement and tend to distribute the load. + */ r = rep; /* be careful */ -- 2.39.2