On 11/8/21 9:12 AM, Lukasz Luba wrote:
...snip
Well, I think the issue is broader. Look at the code which
calculate this 'capacity'. It's just a multiplication & division:
max_capacity = arch_scale_cpu_capacity(cpu); // =1024 in our case
capacity = mult_frac(max_capacity, throttled_freq,
policy->cpuinfo.max_freq);
In the reported by Steev output from sysfs cpufreq we know
that the value of 'policy->cpuinfo.max_freq' is:
/sys/devices/system/cpu/cpu5/cpufreq/cpuinfo_max_freq:2956800
so when we put the values to the equation we get:
capacity = 1024 * 2956800 / 2956800; // =1024
The 'capacity' will be always <= 1024 and this check won't
be triggered:
/* Don't pass boost capacity to scheduler */
if (capacity > max_capacity)
capacity = max_capacity;
IIUC you original code, you don't want to have this boost
frequency to be treated as 1024 capacity. The reason is because
the whole capacity machinery in arch_topology.c is calculated based
on max freq value = 2841600,
so the max capacity 1024 would be pinned to that frequency
(according to Steeve's log:
[ 22.552273] THERMAL_PRESSURE: max_freq(2841) < capped_freq(2956) for
CPUs [4-7] )
Hi Lukasz,
Yes you are right in that I was using policy->cpuinfo.max_freq where as
I should have used freq_factor. So now that you are using freq_factor,
it makes sense to cap the capacity at the max capacity calulated by the
scheduler.
I agree that the problem is complex because at some point we should look
at rebuilding the topology based on changes to policy->cpuinfo.max_freq.
Having all this in mind, the multiplication and division in your
original code should be done:
capacity = 1024 * 2956800 / 2841600; // = 1065
then clamped to 1024 value.
My change just unveiled this division issue.
With that in mind, I tend to agree that I should have not
rely on passed boost freq value and try to apply your suggestion check.
Let me experiment with that...
Regards,
Lukasz
--
Warm Regards
Thara (She/Her/Hers)
