Re: "REPORT: sd-0.46 vs cfs-v6 vs mainline 2.6.21-rc7 Beryl + Video + Audio"

Ingo Molnar
2007-04-27T14:07:46Z

* hechacker1 <hechacker1@gmail.com> wrote:

> "REPORT: sd-0.46 vs cfs-v6 vs mainline 2.6.21-rc7 Beryl + Video + Audio"

thanks for testing it out.

one immediate observation i have is that you used a 2msec granularity
setting on CFS, but even that did not cause context-switching as high as
SD's rr_interval==2 setting:

> cfs-v6:
> 700m kernel # cat sched_granularity_ns
> 2000000
> r b swpd free buff cache si so bi bo in cs us sy id
> 1 0 0 100412 44 1519364 0 0 0 0 7426 7634 62 4 34
> 4 0 0 100288 44 1519364 0 0 0 0 7039 7442 60 6 34

> sd-0.46:
> 700m kernel # cat rr_interval
> 2
> r b swpd free buff cache si so bi bo in cs us sy id
> 5 0 0 918052 536 832840 0 0 411 0 2387 15242 89 11 0
> 4 1 0 915600 536 834908 0 0 388 0 2283 15428 90 10 0

so SD context-switched twice as much and saturated the CPU fully, while
under cfs-v6 there was 34% idle time left. That double context-switch
rate and higher CPU utilization could easily result in you experiencing
a 'smoother' desktop (and smoother video playback) on SD.

could you try to maximize the preemption ratio on CFS by using a
sched_granularity_ns of 0? Does that result in a higher context-switch
rate and in better CPU utilization? Thanks,

Ingo