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Re: [PATCH] netem: fix logic bug in reorder conditional

To: Stephen Hemminger <shemminger@xxxxxxxx>
Subject: Re: [PATCH] netem: fix logic bug in reorder conditional
From: Julio Kriger <juliokriger@xxxxxxxxx>
Date: Tue, 24 May 2005 12:41:11 -0300
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxx, netem@xxxxxxxx
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In-reply-to: <20050523140055.127f1a9f@dxpl.pdx.osdl.net>
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Reply-to: Julio Kriger <juliokriger@xxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
> > 2) If I set latency = 50ms and a jitter = 300ms, tabledist can give me
> > a negative number. This value is addes to cb->time_to_send, so it
> > could change it to a negative value. Should we only accept positives
> > number before add it to cb->time_to_send? or will
> > q->qdisc->enqueue(skb, q->qdisc) put the package on the queue in a
> > special way so it will be handled "before" other packages alrealy on
> > the queue but with gretaer time_to_send?
> 
> probably should bound the value to 0 before the addition, to avoid large
> wraparound problems, but since enqueue checks for for time it will work
> as long as delta less than 2^32/2.
> 

I think the value should be restricted to be positive and greater than
zero. Becuase if a negative number is allowed we will be "losing"
packages to be reordered, hence we will not be reordering, say 25%, of
packages instead we will be reordering about 15%.
In other words, packages that should be reordered will not be
reordered because its new time to send will be the same as the old
time to send.
Regards,
Julio

-- 
----------------------------
Julio Kriger
mailto:juliokriger@xxxxxxxxx


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