diff --git a/ChangeLog b/ChangeLog
index 5d7b694049..d4e1c38cd4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+Wed Sep  3 12:05:17 2014  Tanaka Akira  <akr@fsij.org>
+
+	* process.c (retry_fork_async_signal_safe): Use vfork() if available.
+	  vfork() is still faster than fork() especially when the parent
+	  process uses big memory.
+
+	  ruby -rbenchmark -e 'a = "a" * 1_000_000_000; puts Benchmark.measure { system("true") }'
+	  fork:   0.000000   0.010000   0.010000 (  0.014968)
+	  vfork:  0.000000   0.000000   0.000000 (  0.000912)
+	  on Debian sid.
+
 Wed Sep  3 11:33:08 2014  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
 
 	* test/openssl/test_pkey_rsa.rb (OpenSSL#test_sign_verify_memory_leak):
diff --git a/process.c b/process.c
index 89f829c846..503e73923d 100644
--- a/process.c
+++ b/process.c
@@ -50,6 +50,9 @@
 #ifdef HAVE_SYS_RESOURCE_H
 # include <sys/resource.h>
 #endif
+#ifdef HAVE_VFORK_H
+# include <vfork.h>
+#endif
 #ifdef HAVE_SYS_PARAM_H
 # include <sys/param.h>
 #endif
@@ -3291,7 +3294,11 @@ retry_fork_async_signal_safe(int *status, int *ep,
 
     while (1) {
         prefork();
+#ifdef HAVE_WORKING_VFORK
+        pid = vfork();
+#else
         pid = fork();
+#endif
         if (pid == 0) {/* fork succeed, child process */
             int ret;
             forked_child = 1;
@@ -3305,6 +3312,7 @@ retry_fork_async_signal_safe(int *status, int *ep,
             _exit(127);
 #endif
         }
+        forked_child = 0; /* for vfork(). */
         if (0 < pid) /* fork succeed, parent process */
             return pid;
         /* fork failed */