Add an experiment to measure the likeliness that realloc will avoid a copy.
git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665625 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/test/cpp/realloc/Makefile b/test/cpp/realloc/Makefile
new file mode 100644
index 0000000..57ffb87
--- /dev/null
+++ b/test/cpp/realloc/Makefile
@@ -0,0 +1,21 @@
+# This probably should not go into "make check", because it is an experiment,
+# not a test. Specifically, it is meant to determine how likely realloc is
+# to avoid a copy. This is poorly documented.
+
+run: realloc_test
+ for it in 1 4 64 ; do \
+ for nb in 1 8 64 512 ; do \
+ for mins in 64 512 ; do \
+ for maxs in 2048 262144 ; do \
+ for db in 8 64 ; do \
+ ./realloc_test $$nb $$mins $$maxs $$db $$it \
+ ; done \
+ ; done \
+ ; done \
+ ; done \
+ ; done \
+ > raw_stats
+
+CFLAGS = -Wall -g -std=c99
+LDLIBS = -ldl
+realloc_test: realloc_test.c
diff --git a/test/cpp/realloc/realloc_test.c b/test/cpp/realloc/realloc_test.c
new file mode 100644
index 0000000..7a382b1
--- /dev/null
+++ b/test/cpp/realloc/realloc_test.c
@@ -0,0 +1,88 @@
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+#include <dlfcn.h>
+
+int copies;
+int non_copies;
+
+void *realloc(void *ptr, size_t size) {
+ static void *(*real_realloc)(void*, size_t) = NULL;
+ if (real_realloc == NULL) {
+ real_realloc = (void* (*) (void*, size_t)) dlsym(RTLD_NEXT, "realloc");
+ }
+
+ void *ret_ptr = (*real_realloc)(ptr, size);
+
+ if (ret_ptr == ptr) {
+ non_copies++;
+ } else {
+ copies++;
+ }
+
+ return ret_ptr;
+}
+
+
+struct TMemoryBuffer {
+ void* ptr;
+ int size;
+};
+
+int main(int argc, char *argv[]) {
+ int num_buffers;
+ int init_size;
+ int max_size;
+ int doublings;
+ int iterations;
+
+ if (argc < 6 ||
+ argc > 7 ||
+ (num_buffers = atoi(argv[1])) == 0 ||
+ (init_size = atoi(argv[2])) == 0 ||
+ (max_size = atoi(argv[3])) == 0 ||
+ init_size > max_size ||
+ (iterations = atoi(argv[4])) == 0 ||
+ (doublings = atoi(argv[5])) == 0 ||
+ (argc == 7 && atoi(argv[6]) == 0)) {
+ fprintf(stderr, "usage: realloc_test <num_buffers> <init_size> <max_size> <doublings> <iterations> [seed]\n");
+ exit(EXIT_FAILURE);
+ }
+
+ for ( int i = 0 ; i < argc ; i++ ) {
+ printf("%s ", argv[i]);
+ }
+ printf("\n");
+
+ if (argc == 7) {
+ srand(atoi(argv[6]));
+ } else {
+ srand(time(NULL));
+ }
+
+ struct TMemoryBuffer* buffers = calloc(num_buffers, sizeof(*buffers));
+ if (buffers == NULL) abort();
+
+ for ( int i = 0 ; i < num_buffers ; i++ ) {
+ buffers[i].size = max_size;
+ }
+
+ while (iterations --> 0) {
+ for ( int i = 0 ; i < doublings * num_buffers ; i++ ) {
+ struct TMemoryBuffer* buf = &buffers[rand() % num_buffers];
+ buf->size *= 2;
+ if (buf->size <= max_size) {
+ buf->ptr = realloc(buf->ptr, buf->size);
+ } else {
+ free(buf->ptr);
+ buf->size = init_size;
+ buf->ptr = malloc(buf->size);
+ }
+ if (buf->ptr == NULL) abort();
+ }
+ }
+
+ printf("Non-copied %d/%d (%.2f%%)\n", non_copies, copies + non_copies, 100.0 * non_copies / (copies + non_copies));
+ return 0;
+}