netdev - Re: [PATCH 3/4] Make net watchdog timers 1 sec jiffy aligned

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Date:	Wed, 30 May 2007 11:20:56 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Venki Pallipadi <venkatesh.pallipadi@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 3/4] Make net watchdog timers 1 sec jiffy aligned

On Wed, 30 May 2007 10:59:36 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Tue, 29 May 2007 11:01:13 -0700
> Venki Pallipadi <venkatesh.pallipadi@...el.com> wrote:
> 
> > round_jiffies for net dev watchdog timer.
> > 
> > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
> > 
> > Index: linux-2.6.22-rc-mm/net/sched/sch_generic.c
> > ===================================================================
> > --- linux-2.6.22-rc-mm.orig/net/sched/sch_generic.c	2007-05-24 11:16:03.000000000 -0700
> > +++ linux-2.6.22-rc-mm/net/sched/sch_generic.c	2007-05-25 15:10:02.000000000 -0700
> > @@ -224,7 +224,8 @@
> >  	if (dev->tx_timeout) {
> >  		if (dev->watchdog_timeo <= 0)
> >  			dev->watchdog_timeo = 5*HZ;
> > -		if (!mod_timer(&dev->watchdog_timer, jiffies + dev->watchdog_timeo))
> > +		if (!mod_timer(&dev->watchdog_timer,
> > +			       round_jiffies(jiffies + dev->watchdog_timeo)))
> >  			dev_hold(dev);
> >  	}
> >  }
> 
> Please cc netdev on net patches.
> 
> Again, I worry that if people set the watchdog timeout to, say, 0.1 seconds
> then they will get one second, which is grossly different.
> 
> And if they were to set it to 1.5 seconds, they'd get 2.0 which is pretty
> significant, too.

Alternatively, we could change to a timer that is pushed forward after each
TX, maybe using hrtimer and hrtimer_forward().  That way the timer would
never run in normal case.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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