[patch 4/4] - Potential performance bottleneck for Linxu TCP

[Wenji Wu <wenji@fnal.gov>]

[-- Attachment #1: Type: text/plain, Size: 831 bytes --]

From: Wenji Wu <wenji@fnal.gov>

Greetings,

For Linux TCP, when the network applcaiton make system call to move data
from
socket's receive buffer to user space by calling tcp_recvmsg(). The socket
will
be locked. During the period, all the incoming packet for the TCP socket
will go
to the backlog queue without being TCP processed. Since Linux 2.6 can be
inerrupted mid-task, if the network application expires, and moved to the
expired array with the socket locked, all the packets within the backlog
queue
will not be TCP processed till the network applicaton resume its execution.
If
the system is heavily loaded, TCP can easily RTO in the Sender Side.

Attached is the patch 3/4

best regards,

wenji

Wenji Wu
Network Researcher
Fermilab, MS-368
P.O. Box 500
Batavia, IL, 60510
(Email): wenji@fnal.gov
(O): 001-630-840-4541

[-- Attachment #2: fork.c.patch --]
[-- Type: application/octet-stream, Size: 682 bytes --]

--- linux-2.6.14-old/kernel/fork.c	2006-11-29 16:22:25.000000000 -0600
+++ linux-2.6.14/kernel/fork.c	2006-11-29 11:23:20.000000000 -0600
@@ -868,7 +868,7 @@
  *
  * It copies the registers, and all the appropriate
  * parts of the process environment (as per the clone
- * flags). The actual kick-off is left to the caller.
+ * flags). The actual kick-off is left to the caller.copy_process
  */
 static task_t *copy_process(unsigned long clone_flags,
 				 unsigned long stack_start,
@@ -1154,6 +1154,9 @@
 	write_unlock_irq(&tasklist_lock);
 	retval = 0;
 
+	p->backlog_flag = 0;
+	p->extrarun_flag = 0;
+
 fork_out:
 	if (retval)
 		return ERR_PTR(retval);