On 10/25/10 10:22, Gabriel M. Beddingfield wrote:
On Sunday, October 24, 2010 11:18:45 pm Arjan van de Ven
wrote:
On 10/24/2010 8:39 PM, Gabriel M. Beddingfield wrote:
Hello,
When doing processor intesive calculations (e.g.
synthesizing audio) I've found that the kernel option
CONFIG_X86_ACPI_CPUFREQ causes a big performance drop
when it's enabled.
Any ideas why this is?
is your calculation running "nice"? because if so, you
may get less CPU frequency than the maximum
(which is all you'll get without that CPUFREQ).
OK. That pretty much answers it. See details below.
Anybody know how to configure the speed profile (swich from
"on demand" to "performance"?)
your bug report is rather vague.... can you be more
detailed on which meego you are using,
give us "powertop -d" output while your intensive
calculation is running... and information
on what kind of hardware this is.
When I say "processor intensive" -- I mislead you. I'm
intermittently calculating audio. Whenever it's time to
calculate -- it's intensive and I need a fast response.
When not calculating audio, the application is idle. I.e.
every 5 ms I need to calculate 5 ms of audio. In this case,
5 ms of audio is perhaps 3000-6000 flops.
hehe, yikes!
as Arjan already said, that's terrible from a power consumption
perspective. What you are doing is keeping the CPU out of any C-states
whatsoever (by scheduling to run ever 5ms). Even though you're not
making the CPU busy, you're preventing it from optimally using the
C-states available.
A better algorithm would strike a balance between long sleeps
(seconds...) and short bursts of work (even if it runs for quite a while).
anything else is a loss - switching algorithms at such short interval
would be too
Auke
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