Messages in this thread | | | Date | Mon, 13 Apr 2015 23:42:03 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [patch 4/5] net: hip04: Make tx coalesce timer actually work |
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On Mon, 13 Apr 2015, Arnd Bergmann wrote:
> On Monday 13 April 2015 21:02:23 Thomas Gleixner wrote: > > The code sets the expiry value of the timer to a relative value and > > starts it with hrtimer_start_expires. That's fine, but that only works > > once. The timer is started in relative mode, so the expiry value gets > > overwritten with the absolut expiry time (now + expiry). > > > > So once the timer expired, a new call to hrtimer_start_expires results > > in an immidiately expired timer, because the expiry value is > > already in the past. > > > > Use the proper mechanisms to (re)start the timer in the intended way. > > > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > > Cc: "David S. Miller" <davem@davemloft.net> > > Cc: dingtianhong <dingtianhong@huawei.com> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Zhangfei Gao <zhangfei.gao@linaro.org> > > Cc: Dan Carpenter <dan.carpenter@oracle.com> > > Cc: netdev@vger.kernel.org > > Thanks a lot for the fix. The mistake was clearly mine, as I had sent > a patch to introduce the tx coalesce timer without access to hardware > or a way to test that what I did was correct. > > There are other known problems in the version of the driver that got > merged, and I believe that someone is now looking at them. > > What I think we really want here is a way for user space to configure > both the minimum and maximum coalesce timer separately rather than > assuming half the time is what we want. > > Arnd > > > @@ -413,6 +413,15 @@ out: > > return count; > > } > > > > +static void hip04_start_tx_timer(struct hip04_priv *priv) > > +{ > > + ktime_t t; > > + > > + /* allow timer to fire after half the time at the earliest */ > > + t = ktime_set(0, priv->tx_coalesce_usecs * NSEC_PER_USEC / 2); > > + hrtimer_start(&priv->tx_coalesce_timer, t, HRTIMER_MODE_REL); > > +} > > Question: this looks to me like it sets both the minimum and maximum > time to priv->tx_coalesce_usecs/2, when the intention was to set > the minimum to priv->tx_coalesce_usecs/2 and the maximum to > priv->tx_coalesce_usecs. Am I missing something subtle here, or did > you just misread my original intention from the botched code?
Yes, I missed that. Simple fix for this is:
unsigned long t_ns = priv->tx_coalesce_usecs * NSEC_PER_USEC / 2;
hrtimer_start_range_ns(&priv->tx_coalesce_timer, ns_to_ktime(t_ns), t_ns, HRTIMER_MODE_REL);
Thanks,
tglx
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