path: root/rpc/rpc-lib/src/
diff options
authorKaleb S. KEITHLEY <>2019-03-28 09:36:33 -0400
committerAmar Tumballi <>2019-04-03 04:40:15 +0000
commit024cafea8965086267645be0eae86bcdf5a5d106 (patch)
tree440b86b81dd67f4cc071ccfd2ba97ae285deb5bd /rpc/rpc-lib/src/
parentcada4b432e9373c3ff8423a23c41a455aba4fc4a (diff)
rpclib: slow floating point math and libm
In release-6 rpc/rpc-lib (libgfrpc) added the function get_rightmost_set_bit() which calls log2(3), a call that takes a floating point parameter. It's used thusly: right_most_unset_bit = get_rightmost_set_bit(...); (So is it really the right-most unset bit, or the right-most set bit?) It's unclear to me whether this is in the data path or not. If it is, it's rather scary to think about integer-to-float conversions and slow calls to libm functions in the data path. gcc and clang have __builtin_ctz() which returns the same result as get_rightmost_set_bit(), and does it substantially faster. Approx 20M iterations of get_rightmost_set_bit() took ~33sec of wall clock time on my devel machine, while 20M iterations of __builtin_ctz() took < 9sec; get_rightmost_set_bit() is 3x slower than __builtin_ctz(). And as a side benefit, we can again eliminate the need to link libgfrpc with libm. Change-Id: If9e7e80874577c52223f8125b385fc930de20699 updates: bz#1193929 Signed-off-by: Kaleb S. KEITHLEY <>
Diffstat (limited to 'rpc/rpc-lib/src/')
1 files changed, 1 insertions, 1 deletions
diff --git a/rpc/rpc-lib/src/ b/rpc/rpc-lib/src/
index c7171a260b5..81a96476883 100644
--- a/rpc/rpc-lib/src/
+++ b/rpc/rpc-lib/src/
@@ -8,7 +8,7 @@ libgfrpc_la_SOURCES = auth-unix.c rpcsvc-auth.c rpcsvc.c auth-null.c \
EXTRA_DIST = libgfrpc.sym
libgfrpc_la_LIBADD = $(top_builddir)/libglusterfs/src/ \
- $(top_builddir)/rpc/xdr/src/ $(MATH_LIB)
+ $(top_builddir)/rpc/xdr/src/
libgfrpc_la_LDFLAGS = -version-info $(LIBGFRPC_LT_VERSION) $(GF_LDFLAGS) \
-export-symbols $(top_srcdir)/rpc/rpc-lib/src/libgfrpc.sym