From e98fdfa9a160168d1de8c9a1a3ffebb3fdb4611b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Wed, 6 Oct 2010 21:19:23 +0200
Subject: [PATCH] (overhead): New global variable. (time_function): Compensate
for call overhead. (bench_nothing, time_overhead): New functions.
(time_memxor): Tweaked src size, making it an integral number of words.
(main): Call time_overhead.
Rev: nettle/examples/nettle-benchmark.c:1.13
---
examples/nettle-benchmark.c | 42 ++++++++++++++++++++++++++++++-------
1 file changed, 34 insertions(+), 8 deletions(-)
diff --git a/examples/nettle-benchmark.c b/examples/nettle-benchmark.c
index 4e262629..2195b0e7 100644
--- a/examples/nettle-benchmark.c
+++ b/examples/nettle-benchmark.c
@@ -93,11 +93,15 @@ static double frequency = 0.0;
#define BENCH_ITERATIONS 10
#endif
+static double overhead = 0.0;
+
/* Returns second per function call */
static double
time_function(void (*f)(void *arg), void *arg)
{
unsigned ncalls;
+ double elapsed;
+
#if HAVE_CLOCK_GETTIME && defined CLOCK_PROCESS_CPUTIME_ID
struct timespec before;
struct timespec after;
@@ -121,9 +125,10 @@ time_function(void (*f)(void *arg), void *arg)
}
while (after.tv_sec < done.tv_sec
|| (after.tv_nsec < done.tv_nsec && after.tv_sec == done.tv_sec));
-
- return (after.tv_sec - before.tv_sec
- + 1e-9 * (after.tv_nsec - before.tv_nsec)) / ncalls;
+
+ elapsed = after.tv_sec - before.tv_sec
+ + 1e-9 * (after.tv_nsec - before.tv_nsec);
+
#else /* !HAVE_CLOCK_GETTIME */
clock_t before;
clock_t after;
@@ -140,9 +145,16 @@ time_function(void (*f)(void *arg), void *arg)
ncalls++;
}
while (after < done);
-
- return ((double)(after - before)) / CLOCKS_PER_SEC / ncalls;
+
+ elapsed = (double)(after - before) / CLOCKS_PER_SEC;
#endif /* !HAVE_CLOCK_GETTIME */
+ return elapsed / ncalls - overhead;
+}
+
+static void
+bench_nothing(void *arg UNUSED)
+{
+ return;
}
struct bench_memxor_info
@@ -274,12 +286,24 @@ xalloc(size_t size)
return p;
}
+static void
+time_overhead(void)
+{
+ overhead = time_function(bench_nothing, NULL);
+ printf("benchmark call overhead: %7f us", overhead * 1e6);
+ if (frequency > 0.0)
+ printf("%7.2f cycles\n", overhead * frequency);
+ printf("\n");
+}
+
+
+
static void
time_memxor(void)
{
struct bench_memxor_info info;
- uint8_t src[BENCH_BLOCK + 1];
- uint8_t dst[BENCH_BLOCK + 1];
+ uint8_t src[BENCH_BLOCK + sizeof(long)];
+ uint8_t dst[BENCH_BLOCK];
info.src = src;
info.dst = dst;
@@ -497,9 +521,11 @@ main(int argc, char **argv)
}
alg = argv[optind];
-
+
bench_sha1_compress();
+ time_overhead();
+
header();
if (!alg || strstr ("memxor", alg))
--
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