netdev - Re: [PATCH 2/2]: [NET_SCHED]: Making rate table lookups more flexible.

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Message-Id: <1188829151.16405.10.camel@localhost.localdomain>
Date:	Mon, 03 Sep 2007 16:19:11 +0200
From:	Jesper Dangaard Brouer <jdb@...x.dk>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Jesper Dangaard Brouer <hawk@...u.dk>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2]: [NET_SCHED]: Making rate table lookups more
	flexible.


On Sun, 2007-09-02 at 23:16 +0200, Patrick McHardy wrote:
> Jesper Dangaard Brouer wrote:
> > On Sun, 2 Sep 2007, Patrick McHardy wrote:
> >>
> >
> > Lets focus on the general case, where the functionality actually is 
> > needed right away.
> >
> > In the general case:
> >
> > - The rate table needs to be aligned (cell_align=-1).
> >   (currently, we miscalculates up to 7 bytes on every lookup)
> 
> We will always do that, thats a consequence of storing the
> transmission times for multiples of 8b.

The issue is that we use the lower boundary for calculating the transmit
cost. Thus, a 15 bytes packet only have a transmit cost of 8 bytes.

> > - The existing tc overhead calc can be made more accurate.
> >   (by adding overhead before doing the lookup, instead of the
> >    current solution where the rate table is modified with its
> >    limited resolution)
> 
> Please demonstrate this with patches (one for the overhead
> calculation, one for the cell_align thing), then we can
> continue this discussion.

I have attached a patch for the overhead calculation.

I'll look into the "the cell_align thing" tomorrow.

-- 
Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network developer
  Cand. Scient Datalog / MSc.
  Author of http://adsl-optimizer.dk

View attachment "pkt_sched.h.patch" of type "text/x-patch" (721 bytes)

View attachment "overhead_to_kernel.patch" of type "text/x-patch" (1754 bytes)