[glibc] benchtests: Improve reliability of memcmp benchmarks

[glibc] benchtests: Improve reliability of memcmp benchmarks

[Noah Goldstein]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a1c056c9d06a6aa184fa3c52a5bbd3562ac386e8

commit a1c056c9d06a6aa184fa3c52a5bbd3562ac386e8
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Sat Sep 18 16:13:34 2021 -0500

    benchtests: Improve reliability of memcmp benchmarks
    
    No bug. Remove reallocation of bufs between implementation tests. Move
    initialization outside of foreach implementation test loop. Increase
    iteration count.
    
    Generally before this commit was seeing a great deal of variability
    between runs. The goal of this commit is to make the results more
    reliable.
    
    Benchtests build and bench-memcmp succeeding.
    
    Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>

Diff:
---
 benchtests/bench-memcmp.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/benchtests/bench-memcmp.c b/benchtests/bench-memcmp.c
index 744c7ec5ba..0d6a93bf29 100644
--- a/benchtests/bench-memcmp.c
+++ b/benchtests/bench-memcmp.c
@@ -63,7 +63,7 @@ static void
 do_one_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s1,
 	     const CHAR *s2, size_t len, int exp_result)
 {
-  size_t i, iters = INNER_LOOP_ITERS8;
+  size_t i, iters = INNER_LOOP_ITERS_LARGE;
   timing_t start, stop, cur;
 
   TIMING_NOW (start);
@@ -103,20 +103,19 @@ do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len,
   json_attr_uint (json_ctx, "result", (double) exp_result);
   json_array_begin (json_ctx, "timings");
 
-  FOR_EACH_IMPL (impl, 0)
-    {
-      s1 = (CHAR *) (buf1 + align1);
-      s2 = (CHAR *) (buf2 + align2);
+  s1 = (CHAR *)(buf1 + align1);
+  s2 = (CHAR *)(buf2 + align2);
 
-      for (i = 0; i < len; i++)
-	s1[i] = s2[i] = 1 + (23 << ((CHARBYTES - 1) * 8)) * i % MAX_CHAR;
+  for (i = 0; i < len; i++)
+    s1[i] = s2[i] = 1 + (23 << ((CHARBYTES - 1) * 8)) * i % MAX_CHAR;
 
-      s1[len] = align1;
-      s2[len] = align2;
-      s2[len - 1] -= exp_result;
+  s1[len] = align1;
+  s2[len] = align2;
+  s2[len - 1] -= exp_result;
 
+  FOR_EACH_IMPL (impl, 0)
+    {
       do_one_test (json_ctx, impl, s1, s2, len, exp_result);
-      alloc_bufs ();
     }
 
   json_array_end (json_ctx);