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[PATCH] Add math benchmark latency test
- From: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- To: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Cc: nd <nd at arm dot com>
- Date: Wed, 16 Aug 2017 11:25:15 +0000
- Subject: [PATCH] Add math benchmark latency test
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This patch further improves math function benchmarking by adding a latency
test in addition to throughput. This enables more accurate comparisons of the
math functions. The latency test works by creating a dependency on the previous
iteration: func_res = F (func_res * zero + input[i]). The multiply by zero avoids
changing the input.
The powf test now shows:
"workload-spec2006.wrf": {
"throughput": 200,
"latency": 100
}
OK for commit?
ChangeLog:
2017-08-16 Wilco Dijkstra <wdijkstr@arm.com>
* benchtests/bench-skeleton.c (main): Add support for
latency benchmarking.
* benchtests/scripts/bench.py: Add support for latency benchmarking.
--
diff --git a/benchtests/bench-skeleton.c b/benchtests/bench-skeleton.c
index 3c6dad705594ac0a53edcb4e09686252c13127cf..60753ede1aa3cc05cc0e9eccc74dd12a609a1a67 100644
--- a/benchtests/bench-skeleton.c
+++ b/benchtests/bench-skeleton.c
@@ -71,8 +71,10 @@ main (int argc, char **argv)
bool is_bench = strncmp (VARIANT (v), "workload-", 9) == 0;
double d_total_i = 0;
timing_t total = 0, max = 0, min = 0x7fffffffffffffff;
+ timing_t throughput = 0, latency = 0;
int64_t c = 0;
uint64_t cur;
+ BENCH_VARS;
while (1)
{
if (is_bench)
@@ -86,7 +88,16 @@ main (int argc, char **argv)
BENCH_FUNC (v, i);
TIMING_NOW (end);
TIMING_DIFF (cur, start, end);
- TIMING_ACCUM (total, cur);
+ TIMING_ACCUM (throughput, cur);
+
+ TIMING_NOW (start);
+ for (k = 0; k < iters; k++)
+ for (i = 0; i < NUM_SAMPLES (v); i++)
+ BENCH_FUNC_LAT (v, i);
+ TIMING_NOW (end);
+ TIMING_DIFF (cur, start, end);
+ TIMING_ACCUM (latency, cur);
+
d_total_i += iters * NUM_SAMPLES (v);
}
else
@@ -131,12 +142,15 @@ main (int argc, char **argv)
/* Begin variant. */
json_attr_object_begin (&json_ctx, VARIANT (v));
- json_attr_double (&json_ctx, "duration", d_total_s);
- json_attr_double (&json_ctx, "iterations", d_total_i);
if (is_bench)
- json_attr_double (&json_ctx, "throughput", d_total_s / d_total_i);
+ {
+ json_attr_double (&json_ctx, "throughput", throughput / d_total_i);
+ json_attr_double (&json_ctx, "latency", latency / d_total_i);
+ }
else
{
+ json_attr_double (&json_ctx, "duration", d_total_s);
+ json_attr_double (&json_ctx, "iterations", d_total_i);
json_attr_double (&json_ctx, "max", max / d_iters);
json_attr_double (&json_ctx, "min", min / d_iters);
json_attr_double (&json_ctx, "mean", d_total_s / d_total_i);
diff --git a/benchtests/scripts/bench.py b/benchtests/scripts/bench.py
index 8c1c9eeb2bc67a16cb8a8e010fd2b8a2ef8ab6df..b7ccb7c8c2bf1822202a2377dfb0675516115cc5 100755
--- a/benchtests/scripts/bench.py
+++ b/benchtests/scripts/bench.py
@@ -45,7 +45,7 @@ DEFINES_TEMPLATE = '''
# variant is represented by the _VARIANT structure. The ARGS structure
# represents a single set of arguments.
STRUCT_TEMPLATE = '''
-#define CALL_BENCH_FUNC(v, i) %(func)s (%(func_args)s)
+#define CALL_BENCH_FUNC(v, i, x) %(func)s (x %(func_args)s)
struct args
{
@@ -84,7 +84,9 @@ EPILOGUE = '''
#define RESULT(__v, __i) (variants[(__v)].in[(__i)].timing)
#define RESULT_ACCUM(r, v, i, old, new) \\
((RESULT ((v), (i))) = (RESULT ((v), (i)) * (old) + (r)) / ((new) + 1))
-#define BENCH_FUNC(i, j) ({%(getret)s CALL_BENCH_FUNC (i, j);})
+#define BENCH_FUNC(i, j) ({%(getret)s CALL_BENCH_FUNC (i, j, );})
+#define BENCH_FUNC_LAT(i, j) ({%(getret)s CALL_BENCH_FUNC (i, j, %(latarg)s);})
+#define BENCH_VARS %(defvar)s
#define FUNCNAME "%(func)s"
#include "bench-skeleton.c"'''
@@ -122,17 +124,22 @@ def gen_source(func, directives, all_vals):
# If we have a return value from the function, make sure it is
# assigned to prevent the compiler from optimizing out the
# call.
+ getret = ''
+ latarg = ''
+ defvar = ''
+
if directives['ret']:
print('static %s volatile ret;' % directives['ret'])
- getret = 'ret = '
- else:
- getret = ''
+ print('static %s zero __attribute__((used)) = 0;' % directives['ret'])
+ getret = 'ret = func_res = '
+ latarg = 'func_res * zero +'
+ defvar = '%s func_res = 0;' % directives['ret']
# Test initialization.
if directives['init']:
print('#define BENCH_INIT %s' % directives['init'])
- print(EPILOGUE % {'getret': getret, 'func': func})
+ print(EPILOGUE % {'getret': getret, 'func': func, 'latarg': latarg, 'defvar': defvar })
def _print_arg_data(func, directives, all_vals):