mod_timer improvement

[Steve Modica <modica@xxxxxxx>]

This improves mod_timer scaling quite drastically.  It's already in the 2.6 
kernel.  I've been testing with 8 cpus, 8 threads and 8 cards and mod_timer 
ends up taking up more time than tg_poll without this change.


*** /hosts/bonnie.engr.sgi.com//proj/sgilinux/lbs/isms/linux/linux/kernel/timer.c 2003/08/11 20:16:19 1.23 
--- /hosts/bonnie.engr.sgi.com//proj/sgilinux/lbs/isms/linux/linux/kernel/timer.c 2003/10/01 21:09:20 1.24 *************** 
*** 207,212 **** 
--- 207,220 ---- 
	int ret; 
	unsigned long flags; 

+	/* 
+	* This is a common optimization triggered by the 
+	* networking code - if the timer is re-modified 
+	* to be the same thing then just return: 
+	*/ 
+	if (timer->expires == expires && timer_pending(timer)) 
+	return 1; 
+ 
	spin_lock_irqsave(&timerlist_lock, flags); 
	timer->expires = expires; 
	ret = detach_timer(timer);
--
Steve Modica
work: 651-683-3224
mobile: 651-261-3201
MTS-Technical Lead
"Give a man a fish, and he will eat for a day, hit him with a fish and
he leaves you alone" - me