Best Kernel QoS Parameters

Best Kernel QoS Parameters

[Lucas Willian Bocchi]

Hello all!

I don't know if this is the right list to send this message, but LARTC 
is dead and I believe that this is the only place that I'll have the 
help that I need!

My question is simple: to a linux router, how are the kernel parameters 
(2.6 kernel tree) to set to make a good and responsive kernel to best 
QoS Shaping (HTB, HFSC, etc)?


Another question is: how are the effect of TX and RX Ring Buffer 
(hardware packet buffer) in QoS? The algoritms use these parameters in 
the QoS configuration? I presume that
this parameters can affect the performance, because the hardware buffer 
can borrow the QoS configuration.


Thanks a lot for answer my question. I believe that it's very important 
to newbies in this world (QoS), like me.

[]'s

Re: Best Kernel QoS Parameters

[Michele Petrazzo - Unipex]

Lucas Willian Bocchi wrote:
> Hello all!
> 

Hi,

> My question is simple: to a linux router, how are the kernel 
> parameters (2.6 kernel tree) to set to make a good and responsive 
> kernel to best QoS Shaping (HTB, HFSC, etc)?
> 

 From my point of view, into a  normal environment, the last problem is
which packet scheduler choose. All those are so well builds that when
your setup don't work like you want, the right question must be "where
I'm wrong?" and not "can be the shaper wrong or there is a bug inside?"

For me, for a newbie, the right one are htb. Simple and with a good
documentation / cookbook.

> Another question is: how are the effect of TX and RX Ring Buffer 
> (hardware packet buffer) in QoS? The algoritms use these parameters 
> in the QoS configuration? I presume that this parameters can affect 
> the performance, because the hardware buffer can borrow the QoS 
> configuration.

I haven't read the sources and I'm not a kernel devel, so I don't know
exactly how are the hw buffer use, but I can ensure you that I tried
more than one type of ethernet cards into a heavy use systems (google
for ml archives) and a good card it's one of the best buys that you can do

Michele

Re: Best Kernel QoS Parameters

[Michele Petrazzo - Unipex]

Lucas Willian Bocchi wrote:
> Dear Michelle
> 

Ciao,
Lucas

(I think you forgot to include the netfilter address into the sent)

> Even when you choose your shaper, you need to use the "granularity" of
> kernel to more exact QoS.
> 
> The preferences that I know is
> 
> 1) Preemptible Kernel
> 2) Tickless System
> 3) 1000 HZ Kernel
> 
> With these parameters on, the shaper precision is very, very increased.
> But I think that have another parameters that improve more the speed.
> 

If you talk with hard precision in mind, I'm with you. But into a real
systems like mine, where p.e. if a user as 1Mb bw and the shaper wrong
for 1 or 2 kb, for me it's not a real problem. (admitting that the shape
wrong by a simple 1/2%)

However I didn't know the exists of those parameters... No one doc or
books that I study mentioned them. Also on this ml, if I remember
correctly, no one say to use them.
Seeing like now the default .config found on
arch/x86/configs/x86_64_defconfig anyway the 1000hz and preemptible are
already set. So I'm feeling like!
Next time I'll upgrade my kernel I'll take care to enable also the
tickless parameter!


> Un saluto a tutti italian.
> 

You forgot the last "i" into "italiani". Italian are in English :)

> I'm italian descendent. My father was bird in Napole and bring from
> Brazil very young.
> 

I'm a bit far from Napole, talking with Italian distances, about 1k km.
For understand, near Austria.

Michele

Re: Best Kernel QoS Parameters

[Lucas Willian Bocchi]

Yep. I forgot to include netfilter really. I resend the message to 
netfilter to see this.

The documentation, really, is very poor in this question.

I think that
1) Preemptible Kernel - Hability to the kernel "interrupt" a process to 
insert the scheduler in the processor again (more accuracy)
2) Tickless System - Generate a "timer interrupt" when it is more 
needed. In the scheduler case, make it more "fast".
3) 1000 HZ Kernel - Generate more granularity, inserting a 1ms max 
latency to the tick.

I think that, in the newest version of the kernel, these are the more 
important parameters.

Now, about the hardware: I have, for example:
 ~#~ ethtool -g eth0
Ring parameters for eth0:
Pre-set maximums:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             4096
Current hardware settings:
RX:             256
RX Mini:        0
RX Jumbo:       0
TX:             80

My preocupation is: the Shaper (htb, hfsc, etc) use this parameters in 
your configuration? The programmers have in mind that this buffer can 
affect the eficiency of shaper?
Because if I can enqueue/dequeue packets in the hardware, obviously that 
the Kernel won't have any acknowledgement about these packets. But it 
will affect the QoS in slow lines, such ADSL and others, when the one, 
two or three packets inserted in the hardware layer and ignored by the 
QoS can borrow all the configuration, inserting unknown latencies and 
other problems.

To me, it's very important the precision, because I have clients with 1 
or more MB of link and 56, 48 kbps clients too, and I need to have these 
in mind.

Thanks a lot for all help!




Michele Petrazzo - Unipex escreveu:
> Lucas Willian Bocchi wrote:
>   
>> Dear Michelle
>>
>>     
>
> Ciao,
> Lucas
>
> (I think you forgot to include the netfilter address into the sent)
>
>   
>> Even when you choose your shaper, you need to use the "granularity" of
>> kernel to more exact QoS.
>>
>> The preferences that I know is
>>
>> 1) Preemptible Kernel
>> 2) Tickless System
>> 3) 1000 HZ Kernel
>>
>> With these parameters on, the shaper precision is very, very increased.
>> But I think that have another parameters that improve more the speed.
>>
>>     
>
> If you talk with hard precision in mind, I'm with you. But into a real
> systems like mine, where p.e. if a user as 1Mb bw and the shaper wrong
> for 1 or 2 kb, for me it's not a real problem. (admitting that the shape
> wrong by a simple 1/2%)
>
> However I didn't know the exists of those parameters... No one doc or
> books that I study mentioned them. Also on this ml, if I remember
> correctly, no one say to use them.
> Seeing like now the default .config found on
> arch/x86/configs/x86_64_defconfig anyway the 1000hz and preemptible are
> already set. So I'm feeling like!
> Next time I'll upgrade my kernel I'll take care to enable also the
> tickless parameter!
>
>
>   
>> Un saluto a tutti italian.
>>
>>     
>
> You forgot the last "i" into "italiani". Italian are in English :)
>
>   
>> I'm italian descendent. My father was bird in Napole and bring from
>> Brazil very young.
>>
>>     
>
> I'm a bit far from Napole, talking with Italian distances, about 1k km.
> For understand, near Austria.
>
> Michele
>
>   

Re: Best Kernel QoS Parameters

[Michele Petrazzo - Unipex]

Lucas Willian Bocchi ha scritto:

(sorry for late reply, I was so busy)

> 
> The documentation, really, is very poor in this question.
> 

well said!

> Now, about the hardware: I have, for example: ~#~ ethtool -g eth0 
> Ring parameters for eth0: Pre-set maximums: RX:             4096 RX 
> Mini:        0 RX Jumbo:       0 TX:             4096 Current 
> hardware settings: RX:             256 RX Mini:        0 RX Jumbo: 0
>  TX:             80
> 

I have the same data here, more or less

> My preocupation is: the Shaper (htb, hfsc, etc) use this parameters 
> in your configuration?

I don't know if directly the shaper or the kernel take advantage of
them, but I can say that I tried to use a low card and the result was
so...miserable. Of course with the same programming.

> The programmers have in mind that this buffer can affect the 
> eficiency of shaper?

I think that the best ml for ask this is directly to lkml.org.

> To me, it's very important the precision, because I have clients with
>  1 or more MB of link and 56, 48 kbps clients too, and I need to have
>  these in mind.
> 

Sorry, but have you already tried a setup like that? Before starts I try
here, in office, my server and after seen that worked perfect with about
ten clients, I put it in production and now it's shaping perfectly about
1k htb classes!

Michele

Re: Best Kernel QoS Parameters

[Lucas Willian Bocchi]

Dear Michelle

Even when you choose your shaper, you need to use the "granularity" of 
kernel to more exact QoS.

The preferences that I know is

1) Preemptible Kernel
2) Tickless System
3) 1000 HZ Kernel

With these parameters on, the shaper precision is very, very increased.
But I think that have another parameters that improve more the speed.

Un saluto a tutti italian.

I'm italian descendent. My father was bird in Napole and bring from 
Brazil very young.

Cheers.

Michele Petrazzo - Unipex escreveu:
> Lucas Willian Bocchi wrote:
>> Hello all!
>>
>
> Hi,
>
>> My question is simple: to a linux router, how are the kernel 
>> parameters (2.6 kernel tree) to set to make a good and responsive 
>> kernel to best QoS Shaping (HTB, HFSC, etc)?
>>
>
> From my point of view, into a  normal environment, the last problem is
> which packet scheduler choose. All those are so well builds that when
> your setup don't work like you want, the right question must be "where
> I'm wrong?" and not "can be the shaper wrong or there is a bug inside?"
>
> For me, for a newbie, the right one are htb. Simple and with a good
> documentation / cookbook.
>
>> Another question is: how are the effect of TX and RX Ring Buffer 
>> (hardware packet buffer) in QoS? The algoritms use these parameters 
>> in the QoS configuration? I presume that this parameters can affect 
>> the performance, because the hardware buffer can borrow the QoS 
>> configuration.
>
> I haven't read the sources and I'm not a kernel devel, so I don't know
> exactly how are the hw buffer use, but I can ensure you that I tried
> more than one type of ethernet cards into a heavy use systems (google
> for ml archives) and a good card it's one of the best buys that you 
> can do
>
> Michele
>