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    SubjectRe: [PATCH 3/4] Make net watchdog timers 1 sec jiffy aligned
    From
    From: Patrick McHardy <kaber@trash.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.

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