[LARTC] HTB dequeueing in pairs fixed

[LARTC] HTB dequeueing in pairs fixed

[Andy Furniss]

I posted earlier when I noticed that htb was releasing packets in pairs, 
even though my burst/quantums were 1 pkt.

To fix I set HTB_HYSTERESIS 0 in net/sched/sch_htb.c .

This gives a noticable gain in upstream worst case latency, for me with 
256kbit/s up I used to see +90 sometimes, now it's +45. For the many who 
  have 128 up it should limit them to +90 rather than +180.

Andy.

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Re: [LARTC] HTB dequeueing in pairs fixed

[Stef Coene]

On Saturday 31 January 2004 02:40, Andy Furniss wrote:
> I posted earlier when I noticed that htb was releasing packets in pairs,
> even though my burst/quantums were 1 pkt.
>
> To fix I set HTB_HYSTERESIS 0 in net/sched/sch_htb.c .
>
> This gives a noticable gain in upstream worst case latency, for me with
> 256kbit/s up I used to see +90 sometimes, now it's +45. For the many who
>   have 128 up it should limit them to +90 rather than +180.
Devik told me that disabling hysteresis will give you more accuracy, but you 
will loose speed.  I had to disable hysteresis when I did some bursts tests.
http://docum.org/stef.coene/qos/faq/cache/36.html

Stef

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 "Using Linux as bandwidth manager"
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Re: [LARTC] HTB dequeueing in pairs fixed

[Artūras Šlajus]

Stef Coene wrote:
> Devik told me that disabling hysteresis will give you more accuracy, but you 
> will loose speed.  I had to disable hysteresis when I did some bursts tests.
> http://docum.org/stef.coene/qos/faq/cache/36.html
Maybe this could be set as kernel option and not by editing .c file in next kernel
release?

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Re: [LARTC] HTB dequeueing in pairs fixed

[Alexander Clouter]

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On Jan 31, Art??ras ??lajus wrote:
> Stef Coene wrote:
> >Devik told me that disabling hysteresis will give you more accuracy, but 
> >you will loose speed.  I had to disable hysteresis when I did some bursts 
> >tests.
> >http://docum.org/stef.coene/qos/faq/cache/36.html
>
> Maybe this could be set as kernel option and not by editing .c file in next 
> kernel
> release?
>
can anyone say sysctl?  Might as well add the other variables too if you are 
adding one.

have fun

Alex


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Re: [LARTC] HTB dequeueing in pairs fixed

[Andy Furniss]

Stef Coene wrote:
> On Saturday 31 January 2004 02:40, Andy Furniss wrote:
> 
>>I posted earlier when I noticed that htb was releasing packets in pairs,
>>even though my burst/quantums were 1 pkt.
>>
>>To fix I set HTB_HYSTERESIS 0 in net/sched/sch_htb.c .
>>
>>This gives a noticable gain in upstream worst case latency, for me with
>>256kbit/s up I used to see +90 sometimes, now it's +45. For the many who
>>  have 128 up it should limit them to +90 rather than +180.
> 
> Devik told me that disabling hysteresis will give you more accuracy, but you 
> will loose speed.  I had to disable hysteresis when I did some bursts tests.
> http://docum.org/stef.coene/qos/faq/cache/36.html
> 
> Stef
> 
Yea - I read that a while ago, it's what gave me the idea to try 0, 
after changing jiffies to CPU didn't help. I doubt with my low bandwidth 
on a P200 I will notice much difference in load, others may of course.

Andy.


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Re: [LARTC] HTB dequeueing in pairs fixed

[Stef Coene]

On Saturday 31 January 2004 18:00, Alexander Clouter wrote:
> On Jan 31, Art??ras ??lajus wrote:
> > Stef Coene wrote:
> > >Devik told me that disabling hysteresis will give you more accuracy, but
> > >you will loose speed.  I had to disable hysteresis when I did some
> > > bursts tests.
> > >http://docum.org/stef.coene/qos/faq/cache/36.html
> >
> > Maybe this could be set as kernel option and not by editing .c file in
> > next kernel
> > release?
>
> can anyone say sysctl?  Might as well add the other variables too if you
> are adding one.
I don't know if it's save to change this on the fly.

Stef

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 "Using Linux as bandwidth manager"
     http://www.docum.org/
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Re: [LARTC] HTB dequeueing in pairs fixed

[Alexander Clouter]

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On Feb 01, Stef Coene wrote:
> On Saturday 31 January 2004 18:00, Alexander Clouter wrote:
> > On Jan 31, Art??ras ??lajus wrote:
> > > Stef Coene wrote:
> > > >Devik told me that disabling hysteresis will give you more accuracy, but
> > > >you will loose speed.  I had to disable hysteresis when I did some
> > > > bursts tests.
> > > >http://docum.org/stef.coene/qos/faq/cache/36.html
> > >
> > > Maybe this could be set as kernel option and not by editing .c file in
> > > next kernel
> > > release?
> >
> > can anyone say sysctl?  Might as well add the other variables too if you
> > are adding one.
> I don't know if it's save to change this on the fly.
> 
> Stef
> 
Looking at the source code it simply adds two extra lines (slightly changing 
a calculation, in the case of HTB_HYSTERESIS).  I have downloaded some 
'teach-yerself-linux-hacking' about sysctl and probably when I am looking to 
avoid doing work will have a go :)

Alex

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