From c20fc675dcb3570f5da597115ced5a2a82c71029 Mon Sep 17 00:00:00 2001
From: root <root>
Date: Thu, 23 Oct 2008 04:56:49 +0000
Subject: *** empty log message ***

---
 Changes    |  7 +++++++
 ev.c       | 35 ++++++++---------------------------
 ev_epoll.c | 24 +++++++++++++++++++++---
 ev_poll.c  |  2 ++
 4 files changed, 38 insertions(+), 30 deletions(-)

diff --git a/Changes b/Changes
index b6a771c..fe8324b 100644
--- a/Changes
+++ b/Changes
@@ -1,6 +1,13 @@
 Revision history for libev, a high-performance and full-featured event loop.
 
 WISH? monotonic clocks times/GetTickCount for coarse corrections?
+
+	- further optimise away the EPOLL_CTL_ADD/MOD combo in the epoll
+          backend by assuming the kernel event mask hasn't changed if
+          ADD fails with EEXIST.
+        - use memset to initialise most arrays now and do away with the
+          init functions.
+
 3.45 Tue Oct 21 21:59:26 CEST 2008
 	- disable inotify usage on linux <2.6.25, as it is broken
           (reported by Yoann Vandoorselaere).
diff --git a/ev.c b/ev.c
index 1d041fe..9358364 100644
--- a/ev.c
+++ b/ev.c
@@ -451,6 +451,8 @@ typedef struct
   WL head;
   unsigned char events;
   unsigned char reify;
+  unsigned char emask; /* the epoll backend stores the actual kernel mask in here */
+  unsigned char unused; /* currently unused padding */
 #if EV_SELECT_IS_WINSOCKET
   SOCKET handle;
 #endif
@@ -613,6 +615,9 @@ array_realloc (int elem, void *base, int *cur, int cnt)
   return ev_realloc (base, elem * *cur);
 }
 
+#define array_init_zero(base,count)	\
+  memset ((void *)(base), 0, sizeof (*(base)) * (count))
+
 #define array_needsize(type,base,cur,cnt,init)			\
   if (expect_false ((cnt) > (cur)))				\
     {								\
@@ -665,19 +670,6 @@ queue_events (EV_P_ W *events, int eventcnt, int type)
 
 /*****************************************************************************/
 
-void inline_size
-anfds_init (ANFD *base, int count)
-{
-  while (count--)
-    {
-      base->head   = 0;
-      base->events = EV_NONE;
-      base->reify  = 0;
-
-      ++base;
-    }
-}
-
 void inline_speed
 fd_event (EV_P_ int fd, int revents)
 {
@@ -977,18 +969,6 @@ static int signalmax;
 
 static EV_ATOMIC_T gotsig;
 
-void inline_size
-signals_init (ANSIG *base, int count)
-{
-  while (count--)
-    {
-      base->head   = 0;
-      base->gotsig = 0;
-
-      ++base;
-    }
-}
-
 /*****************************************************************************/
 
 void inline_speed
@@ -2141,11 +2121,12 @@ ev_io_start (EV_P_ ev_io *w)
     return;
 
   assert (("ev_io_start called with negative fd", fd >= 0));
+  assert (("ev_io start called with illegal event mask", !(w->events & ~(EV_IOFDSET | EV_READ | EV_WRITE))));
 
   EV_FREQUENT_CHECK;
 
   ev_start (EV_A_ (W)w, 1);
-  array_needsize (ANFD, anfds, anfdmax, fd + 1, anfds_init);
+  array_needsize (ANFD, anfds, anfdmax, fd + 1, array_init_zero);
   wlist_add (&anfds[fd].head, (WL)w);
 
   fd_change (EV_A_ fd, w->events & EV_IOFDSET | 1);
@@ -2347,7 +2328,7 @@ ev_signal_start (EV_P_ ev_signal *w)
     sigprocmask (SIG_SETMASK, &full, &prev);
 #endif
 
-    array_needsize (ANSIG, signals, signalmax, w->signum, signals_init);
+    array_needsize (ANSIG, signals, signalmax, w->signum, array_init_zero);
 
 #ifndef _WIN32
     sigprocmask (SIG_SETMASK, &prev, 0);
diff --git a/ev_epoll.c b/ev_epoll.c
index 934e8e3..e36dbcc 100644
--- a/ev_epoll.c
+++ b/ev_epoll.c
@@ -57,20 +57,34 @@
 
 #include <sys/epoll.h>
 
+void inline_size
+unsigned_char_init (unsigned char *base, int count)
+{
+  /* memset might be overkill */
+  while (count--)
+    *base++ = 0;
+}
+
 static void
 epoll_modify (EV_P_ int fd, int oev, int nev)
 {
   struct epoll_event ev;
+  unsigned char oldmask;
 
   /*
    * we handle EPOLL_CTL_DEL by ignoring it here
    * on the assumption that the fd is gone anyways
    * if that is wrong, we have to handle the spurious
    * event in epoll_poll.
+   * the fd is later added, we try to ADD it, and, if that
+   * fails, we assume it still has the same eventmask.
    */
   if (!nev)
     return;
 
+  oldmask = anfds [fd].emask;
+  anfds [fd].emask = nev;
+
   ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */
   ev.events   = (nev & EV_READ  ? EPOLLIN  : 0)
               | (nev & EV_WRITE ? EPOLLOUT : 0);
@@ -80,7 +94,7 @@ epoll_modify (EV_P_ int fd, int oev, int nev)
 
   if (expect_true (errno == ENOENT))
     {
-      /* on ENOENT the fd went away, so try to do the right thing */
+      /* if ENOENT then the fd went away, so try to do the right thing */
       if (!nev)
         return;
 
@@ -89,8 +103,9 @@ epoll_modify (EV_P_ int fd, int oev, int nev)
     }
   else if (expect_true (errno == EEXIST))
     {
-      /* on EEXIST we ignored a previous DEL */
-      if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
+      /* EEXIST means we ignored a previous DEL, but the fd is still active */
+      /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
+      if (oldmask == nev || !epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
         return;
     }
 
@@ -122,7 +137,10 @@ epoll_poll (EV_P_ ev_tstamp timeout)
 
       if (expect_false (got & ~want))
         {
+          anfds [fd].emask = want;
+
           /* we received an event but are not interested in it, try mod or del */
+          /* I don't think we ever need MOD, but let's handle it anyways */
           ev->events = (want & EV_READ  ? EPOLLIN  : 0)
                      | (want & EV_WRITE ? EPOLLOUT : 0);
 
diff --git a/ev_poll.c b/ev_poll.c
index 4a9efdc..e9f5e51 100644
--- a/ev_poll.c
+++ b/ev_poll.c
@@ -42,6 +42,8 @@
 void inline_size
 pollidx_init (int *base, int count)
 {
+  /* consider using memset (.., -1, ...), which is pratically guarenteed
+   * to work on all systems implementing poll */
   while (count--)
     *base++ = -1;
 }
-- 
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