From: Gerrit Renker <gerrit@erg.abdn.ac.uk>
To: dccp@vger.kernel.org
Subject: Re: CCID 3 bounded by OS scheduling granularity
Date: Tue, 06 Mar 2007 09:52:01 +0000 [thread overview]
Message-ID: <200703060952.01629@strip-the-willow> (raw)
In-Reply-To: <200701221424.36105@strip-the-willow>
| > I have performed experiments which confirm that
| >
| > 1) when t_ipi < t_gran, the transmit rate is effectively out of control
| > 2) when t_ipi > t_gran, the actual transmit rate is about a factor of 3
| > higher than s/t_ipi would permit.
| >
| > http://www.erg.abdn.ac.uk/users/gerrit/dccp/docs/packet_scheduling/
|
| I've been going over this and wonder if you ever got to the bottom of
| it by instrumenting it or similar as it doesn't make sense to me....
| We add t_ipi to t_nom after each packet so even coarse grained
| scheduling shouldn't do this.
The graphs on that web page are actually the result of instrumenting the kernel.
There are further instrumentation tests, the results of which are on
http://www.erg.abdn.ac.uk/users/gerrit/dccp/docs/impact_of_tx_queue_lenghts/
The problem is not in adding t_ipi, but rather in schedule_timeout which works
at HZ granularity.
prev parent reply other threads:[~2007-03-06 9:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-22 14:24 CCID 3 bounded by OS scheduling granularity Gerrit Renker
2007-03-06 2:30 ` Ian McDonald
2007-03-06 9:52 ` Gerrit Renker [this message]
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