[mythtv-users] System Load/Performance Question

[yan seiner]

Brian Wood wrote:

>On Feb 19, 2006, at 10:00 PM, Brian Wood wrote:
>
>  
>
>>On Feb 19, 2006, at 9:57 PM, Yan Seiner wrote:
>>
>>    
>>
>>>Brian Wood wrote:
>>>
>>>      
>>>
>>>>I don't see any problems there (the cx88 card is not set up in
>>>>MythTV), the only sharing I see is USB, which I'm not using.
>>>>
>>>>I just set up the offending situation again to get these numbers and
>>>>I'm again getting the digital breakup, and occasional audio hits.
>>>>vmstat shows 97 % idle and 0 wa. Mythfrontend shows between 12  
>>>>and 15
>>>>% CPU
>>>>
>>>>
>>>>        
>>>>
>>>Google for PCI latency....  That may give you some relief, or not.
>>>
>>>ISTR you can adjust it via /proc..
>>>
>>>      
>>>
>>OK, I'll do that, thanks.
>>
>>I should have mentioned BTW, I am getting "prebuffering pauses" from
>>the frontend when these glitches happen.
>>    
>>
>
>Also: I've always got a message when ivtv inits:
>
>"Unreasonably low latency timer setting to 64 (was 32)"
>
>I'd always ignored this because I'd seen it in a lot of posted logs,  
>so I more or less assumed it was normal.
>  
>
The way I understand PCI latency, the greater the number, the more time 
slices that slot gets.  So you can increase bandwith by increasing 
latency, by 'buffering' those transfers on the card.  So you can play 
with latencies to give some cards more ability to transfer data.  Too 
short latencies drive overhead to the point where data transfers are 
very slow.

You can do this in the bios for some machines but also via /proc; I 
think linux sets PCI latencies so I'm not sure how the BIOS and linux 
settings work.

--Yan