rmap_fork

Signed-off-by: Peter Xu <peterx@redhat.com>

bsd/rmap_fork.c

@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <signal.h>
+#include <time.h>
+
+#define BUF_SIZE (1UL << 20)    /* 1MB */
+
+unsigned long getns(void)
+{
+    struct timespec tp;
+
+    clock_gettime(CLOCK_MONOTONIC, &tp);
+    return tp.tv_sec * 1000000000 + tp.tv_nsec;
+}
+
+int main(int argc, char *argv[])
+{
+    pid_t *pid_list, pid;
+    unsigned long start;
+    int i, n, ret;
+    char *area;
+
+    if (argc <= 1)
+        return -1;
+    n = atoi(argv[1]);
+    if (n < 10 || n > 1000)
+        return -1;
+
+    pid_list = malloc(sizeof(pid_t) * n);
+    assert(pid_list);
+
+    /* Create a shared range of pages to be mapped by all childs */
+    area = mmap(NULL, BUF_SIZE, PROT_READ|PROT_WRITE,
+                MAP_ANONYMOUS|MAP_SHARED, -1, 0);
+    assert(area);
+    /* Prefault pages */
+    for (i = 0; i < BUF_SIZE; i += 4096)
+        area[i] = i;
+
+    start = getns();
+
+    /* Trigger rmap_add(), expand rmap list */
+    for (i = 0; i < n; i++) {
+        pid = fork();
+        if (!pid) {
+            sleep(100000);
+        }
+        pid_list[i] = pid;
+    }
+
+    /* Shrink rmap list quickly */
+    for (i = 0; i < n; i++) {
+        ret = kill(pid_list[i], SIGKILL);
+        assert(ret == 0);
+    }
+
+    /* Wait until umap shrink done */
+    for (i = 0; i < n; i++) {
+        wait(&ret);
+    }
+
+    start = getns() - start;
+
+    printf("time used: %lu (ms)\n", start / 1000000);
+
+    munmap(area, BUF_SIZE);
+    free(pid_list);
+    return 0;
+}