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Date: Wed, 30 May 2007 14:10:10 -0700 From: Venki Pallipadi <venkatesh.pallipadi@...el.com> To: David Miller <davem@...emloft.net> Cc: kaber@...sh.net, shemminger@...ux-foundation.org, akpm@...ux-foundation.org, venkatesh.pallipadi@...el.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [PATCH 3/4] Make net watchdog timers 1 sec jiffy aligned On Wed, May 30, 2007 at 12:55:51PM -0700, David Miller wrote: > From: Patrick McHardy <kaber@...sh.net> > Date: Wed, 30 May 2007 20:42:32 +0200 > > > Stephen Hemminger wrote: > > >>>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. > > > > > > It seems wasteful to add per-packet overhead for tx timeouts, which > > should be an exception. Do drivers really care about the exact > > timeout value? Compared to a packet transmission time its incredibly > > long anyways .. > > I agree, this change is absolutely rediculious and is just a blind > cookie-cutter change made without consideration of what the code is > doing and what it's requirements are. I hope I could atleast highlight the issue here despite the cookie-cutter patch.. On a totally idle system I have something like 85 wakeups for every 5 seconds which I am trying to reduce (to reduce the power consumption and increase battery life. And 1 interrupt out of 85 happens to be netdev watchdog timer. Thanks, Venki - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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