On Tue, 18 Dec 2007 20:13:28 -0500 (EST)
Parag Warudkar <[email protected]> wrote:
>
> sky2 can use deferrable timer for watchdog - reduces wakeups from idle per
> second.
>
> Signed-off-by: Parag Warudkar <[email protected]>
>
> --- linux-2.6/drivers/net/sky2.c 2007-12-07 10:04:39.000000000 -0500
> +++ linux-2.6-work/drivers/net/sky2.c 2007-12-18 20:07:58.000000000 -0500
> @@ -4230,7 +4230,10 @@
> sky2_show_addr(dev1);
> }
>
> - setup_timer(&hw->watchdog_timer, sky2_watchdog, (unsigned long) hw);
> + hw->watchdog_timer.function = sky2_watchdog;
> + hw->watchdog_timer.data = (unsigned long) hw;
> + init_timer_deferrable(&hw->watchdog_timer);
> +
> INIT_WORK(&hw->restart_work, sky2_restart);
>
> pci_set_drvdata(pdev, hw);
Does it really reduce the wakeup's or only change who gets charged by powertop?
The system is going to wakeup once a second anyway. Looks to me that if the
timer is using round_jiffies(), that setting deferrable just changes the accounting.
My interpretation of the api is:
* round_jiffies() - timer wants to wakeup but isn't precise about when so schedule
on next second when system will wake up anyway;
e.g why meetings are usually scheduled on the hour
* deferrable - timer doesn't have to really wakeup but wants to happen near
a particular time. e.g. "I'll meet you at the pub around 8pm"
Therefore doing deferrable is unnecessary for timers using round_jiffies unless system
is so good at doing timers that it is going to skip doing timer once per second.
--
Stephen Hemminger <[email protected]>
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