[linux-dvb] High CPU load in "top" due to budget_av slot polling

Robert Schedel r.schedel at yahoo.de
Thu Apr 17 17:27:54 CEST 2008


Robert Schedel wrote:

> Is the 250ms timeout an approved limit? Decreasing it would push the
> load further down. Probably it still has to cover slow CAMs as well as a
> stressed PCI bus. Unfortunately, without CAM/CI I cannot make any
> statements myself.

Just got another idea to improve the code: Function 
"saa7146_wait_for_debi_done_sleep" could be reworked to use what is 
known as "truncated binary exponential backoff" algorithm. IOW, on each 
sleep duplicate the period from 1ms until a fixed maximum, e.g. 32ms. 
This way polling ends fast for those users with fast bus/CAM, and those 
requiring 200ms due to slow bus/CAM should not worry about e.g. 216ms 
response time.

My first tests look promising (load goes down to 0). However, is not the 
simple BEB algorithm already patented?

Regards,
Robert




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