patching file benchtests/Makefile
Hunk #1 FAILED at 53.
1 out of 1 hunk FAILED -- saving rejects to file benchtests/Makefile.rej
The next patch would create the file benchtests/bench-memset-zerofill.c,
which already exists!  Applying it anyway.
patching file benchtests/bench-memset-zerofill.c
Hunk #1 FAILED at 1.
1 out of 1 hunk FAILED -- saving rejects to file benchtests/bench-memset-zerofill.c.rej

Reject file benchtests/Makefile.rej:
--- benchtests/Makefile
+++ benchtests/Makefile
@@ -53,7 +53,7 @@ string-benchset := memccpy memchr memcmp memcpy memmem memmove \
 		   strncasecmp strncat strncmp strncpy strnlen strpbrk strrchr \
 		   strspn strstr strcpy_chk stpcpy_chk memrchr strsep strtok \
 		   strcoll memcpy-large memcpy-random memmove-large memset-large \
-		   memcpy-walk memset-walk memmove-walk
+		   memcpy-walk memset-walk memmove-walk memset-zerofill
 
 # Build and run locale-dependent benchmarks only if we're building natively.
 ifeq (no,$(cross-compiling))

Reject file benchtests/bench-memset-zerofill.c.rej:
--- benchtests/bench-memset-zerofill.c
+++ benchtests/bench-memset-zerofill.c
@@ -0,0 +1,128 @@
+/* Measure memset functions with zero fill data.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#define TEST_MAIN
+#define TEST_NAME "memset"
+#define START_SIZE (16 * 1024)
+#define MIN_PAGE_SIZE (getpagesize () + 64 * 1024 * 1024)
+#define TIMEOUT (20 * 60)
+#include "bench-string.h"
+
+#include "json-lib.h"
+
+void *generic_memset (void *, int, size_t);
+typedef void *(*proto_t) (void *, int, size_t);
+
+IMPL (MEMSET, 1)
+IMPL (generic_memset, 0)
+
+static void
+do_one_test (json_ctx_t *json_ctx, impl_t *impl, CHAR *s,
+	     int c1 __attribute ((unused)), int c2 __attribute ((unused)),
+	     size_t n)
+{
+  size_t i, iters = 16;
+  timing_t start, stop, cur;
+
+  TIMING_NOW (start);
+  for (i = 0; i < iters; i += 2)
+    {
+      CALL (impl, s, c1, n);
+      CALL (impl, s, c2, n);
+    }
+  TIMING_NOW (stop);
+
+  TIMING_DIFF (cur, start, stop);
+
+  json_element_double (json_ctx, (double) cur / (double) iters);
+}
+
+static void
+do_test (json_ctx_t *json_ctx, size_t align, int c1, int c2, size_t len)
+{
+  align &= 63;
+  if ((align + len) * sizeof (CHAR) > page_size)
+    return;
+
+  json_element_object_begin (json_ctx);
+  json_attr_uint (json_ctx, "length", len);
+  json_attr_uint (json_ctx, "alignment", align);
+  json_attr_int (json_ctx, "char1", c1);
+  json_attr_int (json_ctx, "char2", c2);
+  json_array_begin (json_ctx, "timings");
+
+  FOR_EACH_IMPL (impl, 0)
+    {
+      do_one_test (json_ctx, impl, (CHAR *) (buf1) + align, c1, c2, len);
+      alloc_bufs ();
+    }
+
+  json_array_end (json_ctx);
+  json_element_object_end (json_ctx);
+}
+
+int
+test_main (void)
+{
+  json_ctx_t json_ctx;
+  size_t i;
+  int c1, c2;
+
+  test_init ();
+
+  json_init (&json_ctx, 0, stdout);
+
+  json_document_begin (&json_ctx);
+  json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
+
+  json_attr_object_begin (&json_ctx, "functions");
+  json_attr_object_begin (&json_ctx, TEST_NAME);
+  json_attr_string (&json_ctx, "bench-variant", "zerofill");
+
+  json_array_begin (&json_ctx, "ifuncs");
+  FOR_EACH_IMPL (impl, 0)
+    json_element_string (&json_ctx, impl->name);
+  json_array_end (&json_ctx);
+
+  json_array_begin (&json_ctx, "results");
+
+  c2 = 0;
+  for (c1 = 0; c1 < 2; c1++)
+    for (i = START_SIZE; i <= MIN_PAGE_SIZE; i <<= 1)
+      {
+	do_test (&json_ctx, 0, c1, c2, i);
+	do_test (&json_ctx, 3, c1, c2, i);
+      }
+
+  json_array_end (&json_ctx);
+  json_attr_object_end (&json_ctx);
+  json_attr_object_end (&json_ctx);
+  json_document_end (&json_ctx);
+
+  return ret;
+}
+
+#include <support/test-driver.c>
+
+#define libc_hidden_builtin_def(X)
+#define libc_hidden_def(X)
+#define libc_hidden_weak(X)
+#define weak_alias(X,Y)
+#undef MEMSET
+#define MEMSET generic_memset
+#include <string/memset.c>