[LARTC] Clock Source Kernel settings in 2.6.22

[LARTC] Clock Source Kernel settings in 2.6.22

[Mario Antonio Garcia]

I wonder if somebody has got good results (accurate shaping) using 2.6.22?

I am testing with 2.6.22.1, and I haven't been able to get accurate shaping.
For instance, I tried:
        $TC qdisc  add  dev  eth0 root handle 1: htb default 1
        $TC class  add  dev  eth0        parent 1:  classid  1:1        htb 
rate 100000kbit ceil 100000kbit burst 24k cburst 24k
        $TC class  add  dev  eth0        parent 1:1 classid 1:10        htb 
rate 20000kbit ceil 20000kbit burst 24k cburst 24k

and class 1:10 shapes the traffic to 19900kbit instead of 20000kbit 
(bandwidth tests made with ftp and iperf)

My corresponding kernel settings are:
CONFIG_GENERIC_TIME=y
CONFIG_CLOCKSOURCE_WATCHDOG=y
CONFIG_DEFAULT_IOSCHED="cfq"
CONFIG_NO_HZ=y
CONFIG_HIGH_RES_TIMERS=y
CONFIG_HPET_TIMER=y
CONFIG_SCHED_SMT=y
CONFIG_SCHED_MC=y
CONFIG_HZ_1000=y
CONFIG_HZ\x1000
# CONFIG_CPU_FREQ is not set
CONFIG_NET_SCHED=y
CONFIG_NET_SCH_FIFO=y

Notice that in 1.26.22 there are new patches for Clock Source:
http://lists.openwall.net/netdev/2007/03/16/22
"These patches convert the packet schedulers to use ktime as only clock 
source and kill off the manual clock source selection. Additionally all 
packet schedulers are converted to use hrtimer-based Watchdogs, greatly 
increasing scheduling precision."


Regards,

Mario Antonio 




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Re: [LARTC] Clock Source Kernel settings in 2.6.22

[Patrick McHardy]

On Wed, 29 Aug 2007, Mario Antonio Garcia wrote:

> I wonder if somebody has got good results (accurate shaping) using 2.6.22?
>
> I am testing with 2.6.22.1, and I haven't been able to get accurate shaping.
> For instance, I tried:
>       $TC qdisc  add  dev  eth0 root handle 1: htb default 1
>       $TC class  add  dev  eth0        parent 1:  classid  1:1        htb 
> rate 100000kbit ceil 100000kbit burst 24k cburst 24k
>       $TC class  add  dev  eth0        parent 1:1 classid 1:10        htb 
> rate 20000kbit ceil 20000kbit burst 24k cburst 24k
>
> and class 1:10 shapes the traffic to 19900kbit instead of 20000kbit 
> (bandwidth tests made with ftp and iperf)


That seems pretty close. What values do you get with older kernels?
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Re: [LARTC] Clock Source Kernel settings in 2.6.22

[Mario Antonio Garcia]

I used to get an average of  18900kbit.
My hope was that these new patches would bring better accuracy.
Notice the 24 cburst. I am just trying to compensate the inaccuracy this 
way. If I remove the cburst, obviously the shape rate I get goes down.

Perhaps I am missing something. I am  just a novice trying to get exact 
bandwidth shaping. I have tested all the clock source types with no good 
results.


Regards,

Mario Antonio

----- Original Message ----- 
From: "Patrick McHardy" <kaber@trash.net>
To: "Mario Antonio Garcia" <dino@webjogger.net>
Cc: <lartc@mailman.ds9a.nl>
Sent: Friday, August 31, 2007 5:43 AM
Subject: Re: [LARTC] Clock Source Kernel settings in 2.6.22


> On Wed, 29 Aug 2007, Mario Antonio Garcia wrote:
>
>> I wonder if somebody has got good results (accurate shaping) using 
>> 2.6.22?
>>
>> I am testing with 2.6.22.1, and I haven't been able to get accurate 
>> shaping.
>> For instance, I tried:
>>       $TC qdisc  add  dev  eth0 root handle 1: htb default 1
>>       $TC class  add  dev  eth0        parent 1:  classid  1:1        htb 
>> rate 100000kbit ceil 100000kbit burst 24k cburst 24k
>>       $TC class  add  dev  eth0        parent 1:1 classid 1:10        htb 
>> rate 20000kbit ceil 20000kbit burst 24k cburst 24k
>>
>> and class 1:10 shapes the traffic to 19900kbit instead of 20000kbit 
>> (bandwidth tests made with ftp and iperf)
>
>
> That seems pretty close. What values do you get with older kernels?
>
>
>
> 




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Re: [LARTC] Clock Source Kernel settings in 2.6.22

[Patrick McHardy]

[Please keep me in CC/To, I don't read lartc often]

Mario Antonio Garcia wrote:
> I used to get an average of  18900kbit.
> My hope was that these new patches would bring better accuracy.

Well, you're up from 94.5% to 99.95%, so they seem to do :)

> Notice the 24 cburst. I am just trying to compensate the inaccuracy 
> this way. If I remove the cburst, obviously the shape rate I get goes 
> down.
>
> Perhaps I am missing something. I am  just a novice trying to get 
> exact bandwidth shaping. I have tested all the clock source types with 
> no good results.

A couple of comments:

- The patches so far only improve things on x86

- Try to test using UDP (not sure if you did) or simply a ping flood,
  TCP is not ideal.

- iproute calculates burst values automatically. With the higher
  precision clock source you can use a smaller value (also done
  automatically if you don't specify them).

- HFSC is more precise than HTB (and not the least more complicated
  to configure if you use only linear service curves)

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