crush: improve straw2 adjustment slightly

This improves the accuracy for low weights especially...

Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/src/crush/mapper.c b/src/crush/mapper.c
index 32486b63c487ea4a0f1e0959d13f9617c01abe86..c409ca1262bad01df81adfa456105fe7d96927dd 100644 (file)
--- a/src/crush/mapper.c
+++ b/src/crush/mapper.c
@@ -322,7 +322,7 @@ static int bucket_straw2_choose(struct crush_bucket_straw2 *bucket,
                 * [0, 0xffff] (corresponding to real numbers
                 * [-11.090355,0]).
                 */
-               ln = crush_ln(u) - 0xfffc;
+               ln = crush_ln(u) - 0x10000;
 
                /*
                 * divide by 16.16 fixed-point weight