Hi Tixy,
I can now reproduce it with MMC too, and the times are pretty much the same for me :(
There is definitely some interaction with CPUFreq, the A7s stay at a low enough OPP that the busy threads during boot are never able to accumulate enough load to migrate up to an A15. Normally, it makes no sense for a thread classified as 'heavy' at 350MHz to move to an A15 since it may very well not be a heavy thread at 1GHz. This is the expected behaviour of the patch, to bring HMP migration in line with cpufreq DVFS changes.
Do you always use the ondemand governor in Linaro? I'm wondering if one of the differences is that the default ondemand config bases it's load calculation on a 1s sliding window, while we use the interactive governor which is much more sensitive.
I'm going to try changing the ondemand config at boot and see what happens.
Regards, Chris
-----Original Message----- From: Jon Medhurst (Tixy) [mailto:tixy@linaro.org] Sent: 20 November 2012 12:31 To: Chris Redpath Cc: Viresh Kumar; Andrey Konovalov; PDSW-power-team; Lists linaro-dev Subject: Re: [GIT PULL]; big LITTLE MP master v12
On Tue, 2012-11-20 at 11:32 +0000, Jon Medhurst (Tixy) wrote:
Tixy, could you try temporarily changing the default option to off
for the frequency-invariant load?
I think it'll be at line 3631 in your fair.c
hmp_data.freqinvar_load_scale_enabled = 1;Change it to 0 to change the default.
That change restores boot time to 90 seconds down from 5-ish minutes.
I'll try booting from a USB stick instead of MMC...
I cloned my MMC card onto a USB stick and updated init.partitions.rc in my initrd to mount sdaX rather than mmblk0pX. Here are the boot times I get:
With hmp_data.freqinvar_load_scale_enabled = 1
49s, 46s, 46s
With hmp_data.freqinvar_load_scale_enabled = 0
39s, 40s, 37s
So whilst the difference is nothing like what I see with MMC, there does still seem to be a significant effect.
On the slow booting config, the 'Geiger counter' sound from the power circuitry does sound a bit harsher, perhaps the pattern of cpuidling is different. That could be my imaginations, or a symptom rather than a cause...
-- Tixy
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