On Wed, Jul 23, 2008 at 7:07 AM, Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:
> Hi,
>
>> Turns out that only implementing a pv get_tsc_khz is not enough, since
>> it will only do the right thing for cpu0, which is not what we desire.
>>
>> So we set preset_lpj. Recall this code is run before arch parameter setup,
>> so if we pass lpj=xx in the command line, it'll still work.
>
> Hmm, why kvm needs the preset_lpj thing and xen doesn't?
I asked myself the same question. But from the snippet in calibrate.c:
if (preset_lpj) {
loops_per_jiffy = preset_lpj;
printk(KERN_INFO
"Calibrating delay loop (skipped) preset value.. ");
} else if ((smp_processor_id() == 0) && lpj_fine) {
loops_per_jiffy = lpj_fine;
printk(KERN_INFO
"Calibrating delay loop (skipped), "
"value calculated using timer frequency.. ");
} else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) {
printk(KERN_INFO
"Calibrating delay using timer specific routine.. ");
The third one is the one we want to skip. The second one, runs only for CPU0.
calibrate_delay_loop() itself, is called very early from smp_callin,
and tsc calibration only sets lpj_fine. So I don't see too much of an
option here.
> cheers,
> Gerd
>
> --
> http://kraxel.fedorapeople.org/xenner/
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--
Glauber Costa.
"Free as in Freedom"
http://glommer.net
"The less confident you are, the more serious you have to act."
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