[vdr] power consumption, powertop and wakups per second with a af9015 device, vp7045, and various plugins

Antti Palosaari crope at iki.fi
Wed Mar 25 21:48:01 CET 2009


Antti Palosaari wrote:
> Heinrich Langos wrote:
>> Moikka Antti,
>>
>>> vp7045 does not have PID-filters.
>>> I think difference comes from different USB-transfer settings. vp7045  
>>> uses BULK packet size 4096 and af9015 uses BULK packet size 512 for  
>>> USB2.0 and BULK packet size 64 for USB1.1. Therefore af9015 sends 8  
>>> times more packets than vp7045 (I guess).
>>>
>>> One thing more you can test - use USB1.1. To force USB1.1 remove USB2.0  
>>> driver by rmmod ehci_hcd. After that plug af9015 stick and look from  
>>> logs it detects USB1.1 and uses PID-filters. af9015 driver now uses  
>>> smaller packet size for transfer that can change load (bigger?).
> 
>> seems you are right. The transfer with PID filter in usb 1.1 causes
>> about 30% load in contrast to 19% with usb 2.0
>>
>> is there a way to increase the packet size for those bulk transfers? 
>> for usb 2.0? for 1.1?
> 
> Actually AF9015 chip offers registers to configure packet size. But 
> those which are now used are default ones and rather many devices (other 
> than af9015) are using just same. That's why I am not sure if I want 
> change those to bigger ones.
> 
> I will make test version that uses 4k packets for your tests. If it 
> resolves problem then we should consider for example adding module param 
> for setting desirable packet size. I will inform you when test version 
> is ready - It takes day or two.

Unfortunately 512 seems to be biggest allowed packet size so I cannot 
increase it. Anyhow, there is other configurable parameter called packet 
count. I increased that from 348 to 512 but I doubt it does not have any 
effect. Feel free to test. If it does not change load then I think we 
cannot do more.
Test tree:
http://linuxtv.org/hg/~anttip/af9015_powertop/

regards
Antti
-- 
http://palosaari.fi/



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