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Re: [Qemu-devel] kqemu vs Standard


From: Jason Brittain
Subject: Re: [Qemu-devel] kqemu vs Standard
Date: Tue, 15 Feb 2005 12:59:29 -0800
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20041020

Magnus Damm wrote:

Interesting!  I wrote the email about all this while riding to work on
the subway.  So, when I did the "cat /proc/cpuinfo", I was indeed running
on battery power.  But, currently, I'm not, and still says the same thing.

Anyone know what the deal is with that?  Is that an accurate number
saying that my cpu is throttled down?  Could I make it run faster then?
Hmmmm..

On a 2.6-kernel with cpufreq enabled, have a look at the files in
"/sys/devices/system/cpu/cpu0/cpufreq/". Try to echo "powersave" or
"performance" to scaling_governor. Then look at "/proc/cpuinfo" to see
the actual MHz.

Ahh, yeah.  I did:

# echo "performance" >> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

And now my /proc/cpuinfo looks like:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 13
model name      : Intel(R) Pentium(R) M processor 1.80GHz
stepping        : 6
cpu MHz         : 1799.038
cache size      : 2048 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr mce cx8 mtrr pge mca cmov pat clflush 
dts acpi mmx fxsr sse sse2 ss tm pbe est tm2
bogomips        : 3563.52

BUT, I retried my tests and the performance numbers/timings came out the same.

You can also play around with acpi throttling in
"/proc/acpi/processor/*/throttling". I guess * should be replaced with
CPU0, but on my crappy laptop with wierd acpi info CPU1 must be used
instead of CPU0.

Also, try cpufreqd or cpudyn to adjust the cpu frequency on the fly.

Thanks for the tips on those.  I'll look into them.

Darryl Dixon wrote:
> That's just the natural effect of the Speedstep technology throttling
> back the cpu to lower heat because you aren't using many cpu cycles at
> the moment (you aren't pushing your laptop very hard :).  If you were to
> do something like, say, compile Wine, and while it is compiling cat
> /proc/cpuinfo, you would see that the speed is up at 1800MHz.

I believe this, since the CPU performance turned out the same either way.
More good info..  thanks!

--
Jason Brittain




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