[PATCH] add concurrent malloc benchmark

[Leonhard Holz <leonhard dot holz at web dot de>]

The current malloc benchtest does use multiple threads, but they work on 
independent block lists so that every thread uses its own arena only. The 
following patch adds a version of the benchmark with all threads working on the 
same block list, so that it is likely that a thread free()s a block in an arena of 
a different thread and by this causes lock contentation on that arena. Therefore 
the performance of the malloc locking mechanism is included in the measuring.

Unfortunately the access to an entry in the shared block list has to be protected 
by a mutex. The time taken for acquiring the mutex is included in the measured 
time per iteration, so that the iteration time of the concurrent malloc benchmark 
is not directly compareable the time of the per-thread benchmark.

	* benchtests/bench-malloc-concurrent.c: New file.
	* benchtests/Makefile: Add bench-malloc-concurrent.

diff --git a/benchtests/Makefile b/benchtests/Makefile
index 08603a2..343e56f 100644
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -44,11 +44,12 @@ benchset := $(string-bench-all) $(stdlib-bench)
 CFLAGS-bench-ffs.c += -fno-builtin
 CFLAGS-bench-ffsll.c += -fno-builtin

-bench-malloc := malloc-thread
+bench-malloc := malloc-thread malloc-concurrent

 $(addprefix $(objpfx)bench-,$(bench-math)): $(libm)
 $(addprefix $(objpfx)bench-,$(bench-pthread)): $(shared-thread-library)
 $(objpfx)bench-malloc-thread: $(shared-thread-library)
+$(objpfx)bench-malloc-concurrent: $(shared-thread-library)

 ^L

@@ -116,10 +117,11 @@ bench-set: $(binaries-benchset)
        done

 bench-malloc: $(binaries-bench-malloc)
-       run=$(objpfx)bench-malloc-thread; \
-       for thr in 1 8 16 32; do \
-         echo "Running $${run} $${thr}"; \
-         $(run-bench) $${thr} > $${run}-$${thr}.out; \
+       for run in $^; do \
+         for thr in 1 8 16 32; do \
+           echo "Running $${run} $${thr}"; \
+           $(run-bench) $${thr} > $${run}-$${thr}.out; \
+         done; \
        done

 # Build and execute the benchmark functions.  This target generates JSON
diff --git a/benchtests/bench-malloc-concurrent.c 
b/benchtests/bench-malloc-concurrent.c
index e69de29..75bd586 100644
--- a/benchtests/bench-malloc-concurrent.c
+++ b/benchtests/bench-malloc-concurrent.c
@@ -0,0 +1,315 @@
+/* Benchmark malloc and free functions.
+   Copyright (C) 2013-2015 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <math.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+#include "bench-timing.h"
+#include "json-lib.h"
+
+/* Benchmark duration in seconds.  */
+#define BENCHMARK_DURATION     60
+#define RAND_SEED              88
+
+#ifndef NUM_THREADS
+# define NUM_THREADS 1
+#endif
+
+/* Maximum memory that can be allocated at any one time is:
+
+   NUM_THREADS * WORKING_SET_SIZE * MAX_ALLOCATION_SIZE
+
+   However due to the distribution of the random block sizes
+   the typical amount allocated will be much smaller.  */
+#define WORKING_SET_SIZE       1024
+
+#define MIN_ALLOCATION_SIZE    4
+#define MAX_ALLOCATION_SIZE    32768
+
+/* Get a random block size with an inverse square distribution.  */
+static unsigned int
+get_block_size (unsigned int rand_data)
+{
+  /* Inverse square.  */
+  const float exponent = -2;
+  /* Minimum value of distribution.  */
+  const float dist_min = MIN_ALLOCATION_SIZE;
+  /* Maximum value of distribution.  */
+  const float dist_max = MAX_ALLOCATION_SIZE;
+
+  float min_pow = powf (dist_min, exponent + 1);
+  float max_pow = powf (dist_max, exponent + 1);
+
+  float r = (float) rand_data / RAND_MAX;
+
+  return (unsigned int) powf ((max_pow - min_pow) * r + min_pow,
+                             1 / (exponent + 1));
+}
+
+static pthread_mutex_t index_lock[WORKING_SET_SIZE];
+
+static void
+init_index_locks (void)
+{
+  for (size_t i = 0; i < WORKING_SET_SIZE; i++)
+    pthread_mutex_init (&index_lock[i], 0);
+}
+
+#define NUM_BLOCK_SIZES        8000
+#define NUM_OFFSETS    ((WORKING_SET_SIZE) * 4)
+
+static unsigned int random_block_sizes[NUM_BLOCK_SIZES];
+static unsigned int random_offsets[NUM_OFFSETS];
+
+static void
+init_random_values (void)
+{
+  for (size_t i = 0; i < NUM_BLOCK_SIZES; i++)
+    random_block_sizes[i] = get_block_size (rand ());
+
+  for (size_t i = 0; i < NUM_OFFSETS; i++)
+    random_offsets[i] = rand () % WORKING_SET_SIZE;
+}
+
+static unsigned int
+get_random_block_size (unsigned int *state)
+{
+  unsigned int idx = *state;
+
+  if (idx >= NUM_BLOCK_SIZES - 1)
+    idx = 0;
+  else
+    idx++;
+
+  *state = idx;
+
+  return random_block_sizes[idx];
+}
+
+static unsigned int
+get_random_offset (unsigned int *state)
+{
+  unsigned int idx = *state;
+
+  if (idx >= NUM_OFFSETS - 1)
+    idx = 0;
+  else
+    idx++;
+
+  *state = idx;
+
+  return random_offsets[idx];
+}
+
+static volatile bool timeout;
+
+static void
+alarm_handler (int signum)
+{
+  timeout = true;
+}
+
+/* Allocate and free blocks in a random order.  */
+static size_t
+malloc_benchmark_loop (void **ptr_arr, size_t start_offset)
+{
+  unsigned int offset_state = start_offset, block_state = 0;
+  size_t iters = 0;
+
+  while (!timeout)
+    {
+      unsigned int next_idx = get_random_offset (&offset_state);
+      unsigned int next_block = get_random_block_size (&block_state);
+
+      pthread_mutex_lock (&index_lock[next_idx]);
+      free (ptr_arr[next_idx]);
+      ptr_arr[next_idx] = malloc (next_block);
+      pthread_mutex_unlock (&index_lock[next_idx]);
+
+      iters++;
+    }
+
+  return iters;
+}
+
+struct thread_args
+{
+  size_t iters;
+  size_t start_offset;
+  void **working_set;
+  timing_t elapsed;
+};
+
+static void *
+benchmark_thread (void *arg)
+{
+  struct thread_args *args = (struct thread_args *) arg;
+  size_t iters;
+  void *thread_set = args->working_set;
+  timing_t start, stop;
+
+  TIMING_NOW (start);
+  iters = malloc_benchmark_loop (thread_set, args->start_offset);
+  TIMING_NOW (stop);
+
+  TIMING_DIFF (args->elapsed, start, stop);
+  args->iters = iters;
+
+  return NULL;
+}
+
+static timing_t
+do_benchmark (size_t num_threads, size_t *iters)
+{
+  timing_t elapsed = 0;
+
+  if (num_threads == 1)
+    {
+      timing_t start, stop;
+      void *working_set[WORKING_SET_SIZE];
+
+      memset (working_set, 0, sizeof (working_set));
+
+      TIMING_NOW (start);
+      *iters = malloc_benchmark_loop (working_set, 0);
+      TIMING_NOW (stop);
+
+      TIMING_DIFF (elapsed, start, stop);
+    }
+  else
+    {
+      struct thread_args args[num_threads];
+      void *working_set[WORKING_SET_SIZE];
+      pthread_t threads[num_threads];
+
+      memset (working_set, 0, sizeof (working_set));
+
+      *iters = 0;
+
+      for (size_t i = 0; i < num_threads; i++)
+       {
+         args[i].working_set = working_set;
+         args[i].start_offset = (WORKING_SET_SIZE / num_threads) * i;
+         pthread_create(&threads[i], NULL, benchmark_thread, &args[i]);
+       }
+
+      for (size_t i = 0; i < num_threads; i++)
+       {
+         pthread_join(threads[i], NULL);
+         TIMING_ACCUM (elapsed, args[i].elapsed);
+         *iters += args[i].iters;
+       }
+    }
+  return elapsed;
+}
+
+static void usage(const char *name)
+{
+  fprintf (stderr, "%s: <num_threads>\n", name);
+  exit (1);
+}
+
+int
+main (int argc, char **argv)
+{
+  timing_t cur;
+  size_t iters = 0, num_threads = 1;
+  unsigned long res;
+  json_ctx_t json_ctx;
+  double d_total_s, d_total_i;
+  struct sigaction act;
+
+  if (argc == 1)
+    num_threads = 1;
+  else if (argc == 2)
+    {
+      long ret;
+
+      errno = 0;
+      ret = strtol(argv[1], NULL, 10);
+
+      if (errno || ret == 0)
+       usage(argv[0]);
+
+      num_threads = ret;
+    }
+  else
+    usage(argv[0]);
+
+  init_index_locks ();
+  init_random_values ();
+
+  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, "malloc");
+
+  json_attr_object_begin (&json_ctx, "");
+
+  TIMING_INIT (res);
+
+  (void) res;
+
+  memset (&act, 0, sizeof (act));
+  act.sa_handler = &alarm_handler;
+
+  sigaction (SIGALRM, &act, NULL);
+
+  alarm (BENCHMARK_DURATION);
+
+  cur = do_benchmark (num_threads, &iters);
+
+  struct rusage usage;
+  getrusage(RUSAGE_SELF, &usage);
+
+  d_total_s = cur;
+  d_total_i = iters;
+
+  json_attr_double (&json_ctx, "duration", d_total_s);
+  json_attr_double (&json_ctx, "iterations", d_total_i);
+  json_attr_double (&json_ctx, "time_per_iteration", d_total_s / d_total_i);
+  json_attr_double (&json_ctx, "max_rss", usage.ru_maxrss);
+
+  json_attr_double (&json_ctx, "threads", num_threads);
+  json_attr_double (&json_ctx, "min_size", MIN_ALLOCATION_SIZE);
+  json_attr_double (&json_ctx, "max_size", MAX_ALLOCATION_SIZE);
+  json_attr_double (&json_ctx, "random_seed", RAND_SEED);
+
+  json_attr_object_end (&json_ctx);
+
+  json_attr_object_end (&json_ctx);
+
+  json_attr_object_end (&json_ctx);
+
+  json_document_end (&json_ctx);
+
+  return 0;
+}