mod_timer improvement

mod_timer improvement

[Steve Modica]

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

Re: mod_timer improvement

[Steve Modica]

D'OH! Sorry about the formatting.  I think this is better:


@@ -207,6 +207,14 @@
         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

Re: mod_timer improvement

[David S. Miller]

On Thu, 02 Oct 2003 12:15:14 -0500
Steve Modica <modica@sgi.com> wrote:

> D'OH! Sorry about the formatting.  I think this is better:

Probably the networking development list isn't the place
to post patches that modify generic code such as the timer
stuff you are modifying here.

mod_timer improvement

[Steve Modica]

Sorry about the screwed up formatting!  I'm kinda new at this :)



*** linux/linux/kernel/timer.c       2003/08/11 20:16:19     1.23
--- linux/linux/kernel/timer.c       2003/10/01 21:09:20     1.24
*************** int mod_timer(struct timer_list *timer,
*** 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