perf bench: Allow passing an iteration count to "bench mem mem{cpy,set}"

"perf stat ... perf bench mem mem..." is pretty meaningless when using
small block sizes (as the overhead of the invocation of each test run
basically hides the actual test result in the noise). Repeating the
actually interesting function's invocation a number of times allows the
results to become meaningful.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4F16D767020000780006D738@nat28.tlf.novell.com
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/tools/perf/bench/mem-memset.c b/tools/perf/bench/mem-memset.c
index 9c0c6f0cba9b..59d4933eff44 100644
--- a/tools/perf/bench/mem-memset.c
+++ b/tools/perf/bench/mem-memset.c
@@ -24,6 +24,7 @@
 
 static const char       *length_str     = "1MB";
 static const char       *routine        = "default";
+static int              iterations      = 1;
 static bool             use_clock;
 static int              clock_fd;
 static bool             only_prefault;
@@ -35,6 +36,8 @@ static const struct option options[] = {
                     "available unit: B, MB, GB (upper and lower)"),
         OPT_STRING('r', "routine", &routine, "default",
                     "Specify routine to copy"),
+        OPT_INTEGER('i', "iterations", &iterations,
+                    "repeat memset() invocation this number of times"),
         OPT_BOOLEAN('c', "clock", &use_clock,
                     "Use CPU clock for measuring"),
         OPT_BOOLEAN('o', "only-prefault", &only_prefault,
@@ -117,6 +120,7 @@ static u64 do_memset_clock(memset_t fn, size_t len, bool prefault)
 {
         u64 clock_start = 0ULL, clock_end = 0ULL;
         void *dst = NULL;
+        int i;
 
         alloc_mem(&dst, len);
 
@@ -124,7 +128,8 @@ static u64 do_memset_clock(memset_t fn, size_t len, bool prefault)
                 fn(dst, -1, len);
 
         clock_start = get_clock();
-        fn(dst, 0, len);
+        for (i = 0; i < iterations; ++i)
+                fn(dst, i, len);
         clock_end = get_clock();
 
         free(dst);
@@ -135,6 +140,7 @@ static double do_memset_gettimeofday(memset_t fn, size_t len, bool prefault)
 {
         struct timeval tv_start, tv_end, tv_diff;
         void *dst = NULL;
+        int i;
 
         alloc_mem(&dst, len);
 
@@ -142,7 +148,8 @@ static double do_memset_gettimeofday(memset_t fn, size_t len, bool prefault)
                 fn(dst, -1, len);
 
         BUG_ON(gettimeofday(&tv_start, NULL));
-        fn(dst, 0, len);
+        for (i = 0; i < iterations; ++i)
+                fn(dst, i, len);
         BUG_ON(gettimeofday(&tv_end, NULL));
 
         timersub(&tv_end, &tv_start, &tv_diff);