[PATCH]: Make UDP wait for 64k of free buffer before telling select/poll there is space to send.

[Ben Greear <greearb@candelatech.com>]

This should allow better handling of large (> 2048 byte) UDP packets
when the socket write buffer is relatively large....

diff -u -r -N -X /home/greear/exclude.list linux/include/net/sock.h linux.dev/include/net/sock.h
--- linux/include/net/sock.h	Fri Dec 21 10:42:04 2001
+++ linux.dev/include/net/sock.h	Sun Dec 23 12:22:52 2001
@@ -1230,7 +1230,16 @@
   */
  static inline int sock_writeable(struct sock *sk)
  {
- 
return sock_wspace(sk) >= SOCK_MIN_WRITE_SPACE;
+   /* The goal is to only signal writable when there is at least 64k of buffer space
+    * when your send buffers are 128k or bigger.  The reason is that otherwise
+    * you get many failed UDP sends when you run > SOCK_MIN_WRITE_SPACE sized packets
+    * at extreme speed (ie faster than your network can keep up).  This change is
+    * designed to make select/poll wait untill you can actually be assured of sending
+    * the UDP packet at least into the kernel buffers w/out dropping it.
+    * This puts us more in line with sock_dev_write_space in core/sock.c too. --Ben
+    */
+   return sock_wspace(sk) >= max(SOCK_MIN_WRITE_SPACE,
+                                 min((unsigned int)(0xFFFF), sk->sndbuf >> 1));
  }

  static inline int gfp_any(void)

-- 
Ben Greear <greearb@candelatech.com>       <Ben_Greear AT excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear