From: Patrick McHardy <kaber@trash.net>
To: leon zadorin <leonleon77@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: "no hz"/"dynamic tick" option and TC/TBF (token bucket filter) behaviour...
Date: Thu, 05 Apr 2007 16:48:41 +0200 [thread overview]
Message-ID: <46150C49.4050800@trash.net> (raw)
In-Reply-To: <26d2cb010704050736y775b6b09g67fd40344cd2208d@mail.gmail.com>
leon zadorin wrote:
> 2) for kernels which do have the aforementioned option enabled: how
> does this affect the "tc" (traffic control) utility and the Token
> Bucket Filter (tbf) queueing discipline (traffic-smoothing)
> behhaviour?
>
> For example, the TBF doco suggests that due to the whole fixed Hz
> thing in the kernel (e.g. 100Hz) the maximum rate of the TBF would
> actually be limited to say 1mbit on Intel arch (with the default
> mtu... but if mtu is incleased, so is the burstiness of the traffic
> which is what TBF is trying to prevent in my deployment scenarios).
> ...
>
> So what about the kernels which use this "dyna tick" option - in such
> a kernel, will there be an interrupt generated (e.g. at microsec.
> precision on most platforms) for every packet's send time (e.g. say at
> TBF's rate is at 25Mbps and one sends out 1KB data packets... will
> there be an interrput generated every... 300 microseconds?)...
No, it doesn't affect the timer resolution. net-2.6.22 includes
patches that switch all qdiscs to hrtimers, which allows to use
much smaller burst rates.
prev parent reply other threads:[~2007-04-05 14:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-05 14:36 "no hz"/"dynamic tick" option and TC/TBF (token bucket filter) behaviour leon zadorin
2007-04-05 14:48 ` Patrick McHardy [this message]
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