From: Wilco Dijkstra <wdijkstr@arm.com>
Date: Tue, 20 Jun 2017 15:26:26 +0000 (+0100)
Subject: Improve math benchmark infrastructure
X-Git-Tag: glibc-2.26~301
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=beb52f502f0477465313675d2a0fbf3962e130b8;p=thirdparty%2Fglibc.git

Improve math benchmark infrastructure

Improve support for math function benchmarking.  This patch adds
a feature that allows accurate benchmarking of traces extracted
from real workloads.  This is done by iterating over all samples
rather than repeating each sample many times (which completely
ignores branch prediction and cache effects).  A trace can be
added to existing math function inputs via
"## name: workload-<name>", followed by the trace.

        * benchtests/README: Describe workload feature.
        * benchtests/bench-skeleton.c (main): Add support for
        benchmarking traces from workloads.
---

diff --git a/ChangeLog b/ChangeLog
index 2d81375287f..80bb1f847e7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-20  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	* benchtests/README: Describe workload feature.
+	* benchtests/bench-skeleton.c (main): Add support for
+	benchmarking traces from workloads.
+
 2017-06-20  Zack Weinberg  <zackw@panix.com>
 
 	* string/string.h (__mempcpy_inline): Delete.
diff --git a/benchtests/README b/benchtests/README
index 2c5f3811359..b015acfd538 100644
--- a/benchtests/README
+++ b/benchtests/README
@@ -102,6 +102,12 @@ the same file by using the `name' directive that looks something like this:
 See the pow-inputs file for an example of what such a partitioned input file
 would look like.
 
+It is also possible to measure throughput of a (partial) trace extracted from
+a real workload.  In this case the whole trace is iterated over multiple times
+rather than repeating every input multiple times.  This can be done via:
+
+  ##name: workload-<name>
+
 Benchmark Sets:
 ==============
 
diff --git a/benchtests/bench-skeleton.c b/benchtests/bench-skeleton.c
index 09eb78df1bc..3c6dad70559 100644
--- a/benchtests/bench-skeleton.c
+++ b/benchtests/bench-skeleton.c
@@ -68,34 +68,50 @@ main (int argc, char **argv)
       clock_gettime (CLOCK_MONOTONIC_RAW, &runtime);
       runtime.tv_sec += DURATION;
 
+      bool is_bench = strncmp (VARIANT (v), "workload-", 9) == 0;
       double d_total_i = 0;
       timing_t total = 0, max = 0, min = 0x7fffffffffffffff;
       int64_t c = 0;
+      uint64_t cur;
       while (1)
 	{
-	  for (i = 0; i < NUM_SAMPLES (v); i++)
+	  if (is_bench)
 	    {
-	      uint64_t cur;
+	      /* Benchmark a real trace of calls - all samples are iterated
+		 over once before repeating.  This models actual use more
+		 accurately than repeating the same sample many times.  */
 	      TIMING_NOW (start);
 	      for (k = 0; k < iters; k++)
-		BENCH_FUNC (v, i);
+		for (i = 0; i < NUM_SAMPLES (v); i++)
+		  BENCH_FUNC (v, i);
 	      TIMING_NOW (end);
-
 	      TIMING_DIFF (cur, start, end);
+	      TIMING_ACCUM (total, cur);
+	      d_total_i += iters * NUM_SAMPLES (v);
+	    }
+	  else
+	    for (i = 0; i < NUM_SAMPLES (v); i++)
+	      {
+		TIMING_NOW (start);
+		for (k = 0; k < iters; k++)
+		  BENCH_FUNC (v, i);
+		TIMING_NOW (end);
 
-	      if (cur > max)
-		max = cur;
+		TIMING_DIFF (cur, start, end);
 
-	      if (cur < min)
-		min = cur;
+		if (cur > max)
+		  max = cur;
 
-	      TIMING_ACCUM (total, cur);
-	      /* Accumulate timings for the value.  In the end we will divide
-	         by the total iterations.  */
-	      RESULT_ACCUM (cur, v, i, c * iters, (c + 1) * iters);
+		if (cur < min)
+		  min = cur;
 
-	      d_total_i += iters;
-	    }
+		TIMING_ACCUM (total, cur);
+		/* Accumulate timings for the value.  In the end we will divide
+		   by the total iterations.  */
+		RESULT_ACCUM (cur, v, i, c * iters, (c + 1) * iters);
+
+		d_total_i += iters;
+	      }
 	  c++;
 	  struct timespec curtime;
 
@@ -117,11 +133,16 @@ main (int argc, char **argv)
 
       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);
+      if (is_bench)
+	json_attr_double (&json_ctx, "throughput", d_total_s / d_total_i);
+      else
+	{
+	  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);
+	}
 
-      if (detailed)
+      if (detailed && !is_bench)
 	{
 	  json_array_begin (&json_ctx, "timings");