Patch for MRI to disable thread timer (and improve performance) when no threads are running

gistfile1.diff

--- eval.c.orig	2008-08-03 20:24:26.000000000 -0700
+++ eval.c	2008-09-02 14:03:15.000000000 -0700
@@ -10761,6 +10761,8 @@
 #endif
 }
 
+static int thread_init;
+
 static void
 rb_thread_restore_context(th, exit)
     rb_thread_t th;
@@ -10801,6 +10803,12 @@
     rb_thread_die(th);
     th->prev->next = th->next;
     th->next->prev = th->prev;
+
+    /* if this is the last ruby thread, stop timer signals */
+    if (th->next == th->prev && th->next == main_thread) {
+      rb_thread_stop_timer();
+      thread_init = 0;
+    }
 }
 
 static int
@@ -12090,8 +12098,6 @@
     return th;
 }
 
-static int thread_init;
-
 #if defined(_THREAD_SAFE)
 static void
 catch_timer(sig)

gistfile2.txt

$ strace -ttT ruby -rubygems -e "require 'eventmachine'; EM.run{ Thread.new{ 500_000.times{1} } }" 2>&1 | egrep '(sigret|setitimer)'
14:03:03.967429 setitimer(ITIMER_VIRTUAL, {it_interval={0, 10000}, it_value={0, 10000}}, NULL) = 0 <0.000006>
14:03:03.980404 rt_sigreturn(0x1a)      = 139788857670280 <0.000005>
14:03:03.992394 rt_sigreturn(0x1a)      = -1 EPERM (Operation not permitted) <0.000005>
14:03:04.004394 rt_sigreturn(0x1a)      = 139788855520512 <0.000008>
14:03:04.016393 rt_sigreturn(0x1a)      = 643135 <0.000007>
14:03:04.019187 setitimer(ITIMER_VIRTUAL, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0 <0.000007>
^C