This is experimental clone() (vs. fork()) patch for mpm-itk apache 2.2.
Really I see no perfomance benefits, but only little RAM. But using
CLONE_VFORK must relax cheduling in theory.

Primary - for experiments with LXC.

(c) Denis Kaganovich, <mahatma@eu.by>
Licensed under the same terms as the rest of Apache (or Anarchy license).

In this version I remove vfork by default die to segfaults.

--- a/server/mpm/itk/itk.c	2012-03-03 16:43:55.000000000 +0300
+++ b/server/mpm/itk/itk.c	2012-03-06 11:49:16.000000000 +0300
@@ -100,6 +100,19 @@
 #define HARD_THREAD_LIMIT 1
 #endif
 
+#ifdef __linux__
+#include <syscall.h>
+#include <linux/version.h>
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,5,49) && defined(CLONE_FS)
+#define ITK_USE_CLONE 1
+static int clone_flags1 = 0, clone_flags2 = 0;
+#else
+#define ITK_USE_CLONE 0
+#endif
+#else
+#define ITK_USE_CLONE 0
+#endif
+
 /* config globals */
 
 static apr_proc_mutex_t *accept_mutex;
@@ -751,7 +764,11 @@ static void child_main(int child_num_arg
          */
 
         {
+#if ITK_USE_CLONE
+            pid_t pid = syscall(SYS_clone, clone_flags1, 0, NULL, NULL), child_pid;
+#else
             pid_t pid = fork(), child_pid;
+#endif
             int status;
             switch (pid) {
             case -1:
@@ -840,6 +857,8 @@ static int make_child(server_rec *s, int
 #ifdef _OSD_POSIX
     /* BS2000 requires a "special" version of fork() before a setuid() call */
     if ((pid = os_fork(ap_unixd_config.user_name)) == -1) {
+#elif ITK_USE_CLONE
+    if ((pid = syscall(SYS_clone, clone_flags2, 0, NULL, NULL)) == -1) {
 #else
     if ((pid = fork()) == -1) {
 #endif
@@ -1404,6 +1423,10 @@ static int itk_pre_config(apr_pool_t *p,
     server_limit = DEFAULT_SERVER_LIMIT;
     ap_daemons_limit = server_limit;
     ap_extended_status = 0;
+#if ITK_USE_CLONE
+    clone_flags1 = SIGCHLD;
+    clone_flags2 = SIGCHLD | CLONE_FS;
+#endif
 
     return OK;
 }
@@ -1767,6 +1790,19 @@ static const char *set_chroot(cmd_parms
     return NULL;
 }
 
+#if ITK_USE_CLONE
+static const char *set_clone_flags(cmd_parms *cmd, void *dummy, const char *flags1,  const char *flags2)
+{
+    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+    if (err != NULL)
+        return err;
+
+    clone_flags1 = (SIGCHLD) ^ atoi(flags1);
+    clone_flags2 = (SIGCHLD | CLONE_FS) ^ (flags2 ? atoi(flags2) : 0);
+    return NULL;
+}
+#endif
+
 static const command_rec itk_cmds[] = {
 LISTEN_COMMANDS,
 AP_INIT_TAKE1("StartServers", set_daemons_to_start, NULL, RSRC_CONF,
@@ -1789,6 +1825,10 @@ AP_INIT_TAKE1("MaxClientsVHost", set_max
               "Maximum number of children alive at the same time for this virtual host."),
 AP_INIT_TAKE1("NiceValue", set_nice_value, NULL, RSRC_CONF|ACCESS_CONF,
               "Set nice value for the given vhost, from -20 (highest priority) to 19 (lowest priority)."),
+#if ITK_USE_CLONE
+AP_INIT_TAKE12("CloneFlags", set_clone_flags, NULL, RSRC_CONF,
+              "XOR to default (SIGCHLD, SIGCHLD|CLONE_FS) clone flags. See /usr/include/{linux,bits}/sched.h or 'man 2 clone'"),
+#endif
 AP_GRACEFUL_SHUTDOWN_TIMEOUT_COMMAND,
 { NULL }
 };