Re: tvtime and the Linux 2.6 scheduler

[Nick Piggin <nickpiggin@yahoo.com.au>]

Ingo Molnar wrote:
> * Con Kolivas <kernel@kolivas.org> wrote:
> 
> 
>>>     33 ms : time per NTSC frame
>>
>>snip
>>
>>The followup email from someone describing good performance may help
>>us understand what's going on. Your example of poor performance is one
>>when the cpu performance is marginal to get exactly 30 fps processed
>>and on the screen. The cpu overhead in 2.6 is slightly higher than 2.4
>>so a borderline case may be just pushed over. 
> 
> 
> most of the cpu overhead comes from HZ=1000. Especial with SCHED_FIFO
> there should be minimal (if any) impact from the scheduler changes -
> SCHED_FIFO tasks get all CPU time, no ifs and whens.
> 
> could people who experience tvtime performance problems apply the patch
> below to change HZ back to 100? Does it have any impact?
> 

Just one other thing - realtime scheduling was basically broken up
until around 2.6.5. Before starting any tests, please ensure first
that you are using at least the 2.6.5 kernel. Thanks.