netdev - Re: HTB accuracy for high speed

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Message-ID: <298f5c050905180736m303f0c79ha30d3f791222fa1b@mail.gmail.com>
Date:	Mon, 18 May 2009 15:36:00 +0100
From:	Antonio Almeida <vexwek@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	netdev@...r.kernel.org, kaber@...sh.net, davem@...emloft.net,
	devik@....cz
Subject: Re: HTB accuracy for high speed

This patch works perfectly!
rate (bits/s) is now decreasing along with pps when I stop the traffic
(doesn't grow as it used to for rates over 500Mbtis/s).

# tc -s -d class ls dev eth1 | head -21 | tail -1
 rate 651960Kbit 97482pps backlog 0b 0p requeues 0
 rate 541134Kbit 80911pps backlog 0b 0p requeues 0
 rate 405850Kbit 60683pps backlog 0b 0p requeues 0
 rate 304388Kbit 45512pps backlog 0b 0p requeues 0
 rate 304388Kbit 45512pps backlog 0b 0p requeues 0
 rate 228291Kbit 34134pps backlog 0b 0p requeues 0
 rate 171218Kbit 25601pps backlog 0b 0p requeues 0
 rate 171218Kbit 25601pps backlog 0b 0p requeues 0
 rate 128414Kbit 19201pps backlog 0b 0p requeues 0
 rate 96310Kbit 14400pps backlog 0b 0p requeues 0
 rate 96310Kbit 14400pps backlog 0b 0p requeues 0
 rate 72233Kbit 10800pps backlog 0b 0p requeues 0
 rate 54174Kbit 8100pps backlog 0b 0p requeues 0


Thank's to you!
  Antonio Almeida




On Sat, May 16, 2009 at 3:14 PM, Jarek Poplawski <jarkao2@...il.com> wrote:
> On Fri, May 15, 2009 at 03:49:31PM +0100, Antonio Almeida wrote:
> ...
>> I also note that, for HTB rate configurations over 500Mbit/s on leaf
>> class, when I stop the traffic, in the output of "tc -s -d class ls
>> dev eth1" command, I see that leaf's rate (in bits/s) is growing
>> instead of decreasing (as expected since I've stopped the traffic).
>> Rate in pps is ok and decreases until 0pps. Rate in bits/s increases
>> above 1000Mbit and stays there for a few minutes. After two or three
>> minutes it becomes 0bit. The same happens for it's ancestors (also for
>> root class).Here's tc output of my leaf class for this situation:
>>
>> class htb 1:108 parent 1:10 leaf 108: prio 7 quantum 1514 rate
>> 555000Kbit ceil 555000Kbit burst 70901b/8 mpu 0b overhead 0b cburst
>> 70901b/8 mpu 0b overhead 0b level 0
>>  Sent 120267768144 bytes 242475339 pkt (dropped 62272599, overlimits 0
>> requeues 0)
>>  rate 1074Mbit 0pps backlog 0b 0p requeues 0
>>  lended: 242475339 borrowed: 0 giants: 0
>>  tokens: 8 ctokens: 8
>
> This looks like a regular bug. I guess it's an overflow in
> gen_estimator(), but I'm not sure there is nothing more. Could you
> try the patch below? (An offset warning when patching 2.6.25 is OK)
>
> Thanks,
> Jarek P.
> ---
>
>  net/core/gen_estimator.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
> index 9cc9f95..87f0ced 100644
> --- a/net/core/gen_estimator.c
> +++ b/net/core/gen_estimator.c
> @@ -127,7 +127,11 @@ static void est_timer(unsigned long arg)
>                npackets = e->bstats->packets;
>                rate = (nbytes - e->last_bytes)<<(7 - idx);
>                e->last_bytes = nbytes;
> -               e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log;
> +               if (rate > e->avbps)
> +                       e->avbps += (rate - e->avbps) >> e->ewma_log;
> +               else
> +                       e->avbps -= (e->avbps - rate) >> e->ewma_log;
> +
>                e->rate_est->bps = (e->avbps+0xF)>>5;
>
>                rate = (npackets - e->last_packets)<<(12 - idx);
>
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