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From: Jesper Dangaard Brouer <jdb@comx.dk>
To: "Dave Täht" <d@taht.net>
Cc: bloat-devel@lists.bufferbloat.net, herbert@gondor.apana.org.au,
	Van Jacobson <van@parc.com>,
	shalunov@shlang.com, bloat@lists.bufferbloat.net
Subject: Re: [Bloat] GSO
Date: Wed, 02 Mar 2011 09:30:24 +0100	[thread overview]
Message-ID: <1299054624.5900.36.camel@blue> (raw)
In-Reply-To: <87aahj7c0c.fsf@cruithne.co.teklibre.org>

On Sat, 2011-02-26 at 03:41 +0100, Dave Täht wrote:
> Jesper Dangaard Brouer <hawk@comx.dk> writes:
> > On Fri, 2011-02-25 at 17:33 +0100, Eric Dumazet wrote:
> >> Le vendredi 25 février 2011 à 16:48 +0100, Jesper Dangaard Brouer a
> >> écrit :
> >>
> >> > Disabling GSO on speed server fixed the problem as can be seen on graph:
> >> > http://people.netfilter.org/hawk/dropbox/bloat_vs_GSO/speed-to-grantoften-solved.png
> >> >
> >> > The really strange part when troubleshooting this issue was that the
> >> > throughput as fine between the two customer end-boxes ("grantoften" and
> >> > "pc314a") as can be see here:
> >> > http://people.netfilter.org/hawk/dropbox/bloat_vs_GSO/pc314a-to-grantoften-1.png
> >> >
...
> > The graph is generated (with GNUplot) with data from the
> > throughput-latency tool called "thrulay".  Its created by Stanislav
> > Shalunov, and its homepage is here: http://shlang.com/thrulay/
> >
> > I really love this "thrulay" tool, as it measure both the throughput and
> > records the TCP sessions experienced delay.  And the output can be used
> > directly by GNUplot. Nice! :-)
> 
> I find the 10ms granularity on both graphs rather interesting. One of my
> issues with HTB (when last I checked) is that it does odd things across
> the clock interval.

This case/graphs have nothing to do with the HTB qdisc.  The traffic is
not affected by the HTB shaper (on the path) as the customer actually
have a 110Mbit/s bandwidth limit (as we always give customers 10% extra
to avoid any complaints about overhead).

If I change the customers bandwidth to 90 Mbit/s or 93 Mbit/s, which
makes the HTB shaper (+the SFQ scheduler) have effect, then the customer
experience is perfect, as I have solved the bufferbloat issue.  The
problem is of cause that marketing want to sell 100Mbit/s, not 90Mbit/s
or 93Mbit/s. Thus, I cannot really implement the fix :-(.

But, you memory is not totally faulted regrading HTB ;-)
HTB used to be affected by the HZ clock interval, but I think Stephen
Hemminger fixed that by using the highres timer API.  And I fixed the
"no_hyst" case where HTB could introduce spikes of three times the
expected delay.


--
Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network Kernel Developer
  Cand. Scient Datalog / MSc.CS
  Author of http://adsl-optimizer.dk
  LinkedIn: http://www.linkedin.com/in/brouer



  reply	other threads:[~2011-03-02  8:31 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-24 14:19 [Bloat] Please enter issues into the issue tracker - Issue system organisation needed Jim Gettys
2011-02-24 15:00 ` Fred Baker
2011-02-24 16:32   ` Jim Gettys
2011-02-24 17:08     ` Eric Dumazet
2011-02-24 18:31       ` Dave Täht
2011-02-24 19:29         ` Eric Dumazet
2011-02-25 10:12           ` [Bloat] smokeping for Windows Seth Teller
2011-02-25 10:51             ` Jim Gettys
2011-02-25 11:21           ` [Bloat] GSO (was: Please enter issues into the issue tracker - Issue system organisation needed) Jesper Dangaard Brouer
2011-02-25 11:54             ` Eric Dumazet
2011-02-25 15:48               ` Jesper Dangaard Brouer
2011-02-25 16:19                 ` Eric Dumazet
2011-02-25 16:33                 ` Eric Dumazet
2011-02-25 17:15                   ` Jesper Dangaard Brouer
2011-02-26  2:41                     ` [Bloat] GSO Dave Täht
2011-03-02  8:30                       ` Jesper Dangaard Brouer [this message]
2011-03-04  2:23                         ` Dave Täht
2011-02-25 15:40         ` [Bloat] Please enter issues into the issue tracker - Issue system organisation needed John W. Linville

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