Use HP_TIMING for benchmarks if available

HP_TIMING uses native timestamping instructions if available, thus
greatly reducing the overhead of recording start and end times for
function calls.  For architectures that don't have HP_TIMING
available, we fall back to the clock_gettime bits.  One may also
override this by invoking the benchmark as follows:

  make USE_CLOCK_GETTIME=1 bench

and get the benchmark results using clock_gettime.  One has to do
`make bench-clean` to ensure that the benchmark programs are rebuilt.

1 files changed, 72 insertions, 0 deletions

diff --git a/benchtests/bench-timing.h b/benchtests/bench-timing.h
new file mode 100644
index 0000000..264d4b8
--- /dev/null
+++ b/benchtests/bench-timing.h
@@ -0,0 +1,72 @@
+/* Define timing macros.
+   Copyright (C) 2013 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/>.  */
+
+#include <hp-timing.h>
+#include <stdint.h>
+
+#if HP_TIMING_AVAIL && !defined USE_CLOCK_GETTIME
+# define GL(x) _##x
+# define GLRO(x) _##x
+hp_timing_t _dl_hp_timing_overhead;
+typedef hp_timing_t timing_t;
+
+# define TIMING_INIT(iters) \
+({									      \
+  HP_TIMING_DIFF_INIT();						      \
+  (iters) = 1000;							      \
+})
+
+# define TIMING_NOW(var) HP_TIMING_NOW (var)
+# define TIMING_DIFF(diff, start, end) HP_TIMING_DIFF ((diff), (start), (end))
+# define TIMING_ACCUM(sum, diff) HP_TIMING_ACCUM_NT ((sum), (diff))
+
+# define TIMING_PRINT_STATS(func, d_total_s, d_iters, d_total_i, max, min) \
+  printf ("%s: ITERS:%g: TOTAL:%gMcy, MAX:%gcy, MIN:%gcy, %g calls/Mcy\n",    \
+	  (func), (d_total_i), (d_total_s) * 1e-6, (max) / (d_iters),	      \
+	  (min) / (d_iters), 1e6 * (d_total_i) / (d_total_s));
+
+#else
+typedef uint64_t timing_t;
+
+/* Measure 1000 times the resolution of the clock.  So for a 1ns
+   resolution  clock, we measure 1000 iterations of the function call at a
+   time.  Measurements close to the minimum clock resolution won't make
+   much sense, but it's better than having nothing at all.  */
+# define TIMING_INIT(iters) \
+({									      \
+  struct timespec start;						      \
+  clock_getres (CLOCK_PROCESS_CPUTIME_ID, &start);			      \
+  (iters) = 1000 * start.tv_nsec;					      \
+})
+
+# define TIMING_NOW(var) \
+({									      \
+  struct timespec tv;							      \
+  clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &tv);			      \
+  (var) = (uint64_t) (tv.tv_nsec + (uint64_t) 1000000000 * tv.tv_sec);	      \
+})
+
+# define TIMING_DIFF(diff, start, end) (diff) = (end) - (start)
+# define TIMING_ACCUM(sum, diff) (sum) += (diff)
+
+# define TIMING_PRINT_STATS(func, d_total_s, d_iters, d_total_i, max, min) \
+  printf ("%s: ITERS:%g: TOTAL:%gs, MAX:%gns, MIN:%gns, %g iter/s\n",	      \
+	  (func), (d_total_i), (d_total_s) * 1e-9, (max) / (d_iters),		      \
+	  (min) / (d_iters), 1e9 * (d_total_i) / (d_total_s))
+
+#endif