Messages in this thread | | | Date | Mon, 4 Mar 2019 13:58:12 +0000 | From | Quentin Perret <> | Subject | Re: 答复: [PATCH V4] sc hed/cpufreq: initializ e iowait_boost_max and iowait_boost with cpu capacity |
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On Monday 04 Mar 2019 at 07:35:04 (+0000), Wang, Vincent (王争) wrote: > Did you mean the value of arch_scale_cpu_capacity() is changed in > cpu_capacity_store()?
Yes, there's that, but more importantly topology_normalize_cpu_scale() is called during boot. With printks() in the relevant functions, the boot log on my system with two CPUFreq policies looks like this:
[ 2.393085] init_cpu_capacity_callback: policy0 [ 2.397714] sugov_start: policy0 [ 2.403734] init_cpu_capacity_callback: policy1 [ 2.407901] topology_normalize_cpu_scale: done [ 2.412581] sugov_start: policy1
So, the lack of order of sugov_start() and topology_normalize_cpu_scale() is a problem, I think.
> If so, I can restart schedutil governor after new capacity is updated.
Hmm, that feels a bit overkill, but that should at least be a correct way of updating sg_cpu->{min, max} in a non-racy way. And CPU capacity changes are infrequent, so the overhead of re-starting the governor isn't a major issue, I suppose.
You could also update the values in sugov_get_util() at the cost of a small overhead to compute 'min'. I'm not sure what's preferable since we wanted to avoid that kind of overhead in the first place ...
Thanks, Quentin
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