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authorTorvald Riegel <triegel@redhat.com>2013-10-08 14:17:01 +0300
committerTorvald Riegel <triegel@redhat.com>2014-04-10 21:22:28 +0200
commit6a5d6ea128153f5a00d8c80f15f76004006767da (patch)
tree74bf61305b9ec52b30373226cf7a1fcbcec8d27c /benchtests
parenta4c75cfd56e536c2b18556e8a482d88dffa0fffc (diff)
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benchtests: Add pthread_once common-case test.
We have a single thread that runs a no-op initialization once and then repeatedly runs checks of the initialization (i.e., an acquire load and conditional jump) in a tight loop. This gives us, on average, the best-case latency of pthread_once (the initialization is the exactly-once slow path, and we're not looking at initialization-related synchronization overheads in this case).
Diffstat (limited to 'benchtests')
-rw-r--r--benchtests/Makefile3
-rw-r--r--benchtests/README2
-rw-r--r--benchtests/pthread_once-inputs9
-rw-r--r--benchtests/pthread_once-source.c25
4 files changed, 38 insertions, 1 deletions
diff --git a/benchtests/Makefile b/benchtests/Makefile
index ca635cf..6e3f86b 100644
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -23,7 +23,7 @@ subdir := benchtests
include ../Makeconfig
bench := acos acosh asin asinh atan atanh cos cosh exp exp2 ffs ffsll \
- log log2 modf pow rint sin sincos sinh sqrt tan tanh
+ log log2 modf pow pthread_once rint sin sincos sinh sqrt tan tanh
# String function benchmarks.
string-bench := bcopy bzero memccpy memchr memcmp memcpy memmem memmove \
@@ -53,6 +53,7 @@ LDLIBS-bench-exp2 = -lm
LDLIBS-bench-log = -lm
LDLIBS-bench-log2 = -lm
LDLIBS-bench-pow = -lm
+LDLIBS-bench-pthread_once = -lpthread
LDLIBS-bench-rint = -lm
LDLIBS-bench-sin = -lm
LDLIBS-bench-sinh = -lm
diff --git a/benchtests/README b/benchtests/README
index 2a940fa..52a3cc2 100644
--- a/benchtests/README
+++ b/benchtests/README
@@ -60,6 +60,8 @@ one to add `foo' to the bench tests:
- include-sources: This should be assigned a comma-separated list of source
files that need to be included to provide definitions of global variables
and functions (specifically, this includes using "#include "source").
+ See pthread_once-inputs and pthreads_once-source.c for an example of how
+ to use this to benchmark a function that needs state across several calls.
- name: See following section for instructions on how to use this directive.
Lines beginning with a single hash '#' are treated as comments. See
diff --git a/benchtests/pthread_once-inputs b/benchtests/pthread_once-inputs
new file mode 100644
index 0000000..22c5709
--- /dev/null
+++ b/benchtests/pthread_once-inputs
@@ -0,0 +1,9 @@
+# This tests the common-case scenario for pthread_once.
+# We have a single thread that runs a no-op initialization once and then
+# repeatedly runs checks of the initialization (i.e., an acquire load and
+# conditional jump) in a tight loop.
+# scripts/bench.py doesn't handle function pointers, so we just use void *:
+## args: pthread_once_t *:void *
+## includes: pthread.h
+## include-sources: pthread_once-source.c
+&once, once_handler
diff --git a/benchtests/pthread_once-source.c b/benchtests/pthread_once-source.c
new file mode 100644
index 0000000..5f98b0a
--- /dev/null
+++ b/benchtests/pthread_once-source.c
@@ -0,0 +1,25 @@
+/* Measure pthread_once best-case latency (i.e., when already initialized.
+
+ Copyright (C) 2014 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+static pthread_once_t once = PTHREAD_ONCE_INIT;
+
+static void
+once_handler (void)
+{
+}