[pve-devel] applied: [PATCH manager] ui: RRD graphs: display PSI as percent

[Friedrich Weber]

On 31/07/2025 16:08, Shannon Sterz wrote:
> On Thu Jul 31, 2025 at 3:56 PM CEST, Thomas Lamprecht wrote:
>> On Thu, 31 Jul 2025 15:51:42 +0200, Friedrich Weber wrote:
>>> Pressure stall information are actually in percent. This is not
>>> mentioned explicitly in the documentation, but e.g. in the kernel
>>> source [1]:
>>>
>>>> The percentage of wall clock time spent in those compound stall
>>>> states gives pressure numbers between 0 and 100 for each resource,
>>>> where the SOME percentage indicates workload slowdowns and the FULL
>>>> percentage indicates reduced CPU utilization:
>>>>
>>>> 	%SOME = time(SOME) / period
>>>> 	%FULL = time(FULL) / period
>>>
>>> [...]
>>
>> This was a bit strange for me, I seemingly ingrained some wrong knownledge when
>> getting first exposed to PSI when that was a new thing back in 2019 or so,
>> either the docs where worded a bit differently or I just read a bit to much
>> into the wording (more likely), anyhow thanks for clarifying this, one thing
>> that I'm still wondering is this then percent for real (i.e. * 100 already) or
>> a ratio? Or would we need to do *= 100 scaling?
>>
>> Anyway, as this restores the status quo with rationale it's already an
>> improvement as is, so: Applied, thanks!
> 
> if i remember correctly and read the kernel documentation correctly,
> this is proper percent (%) [1]. so no additional multiplying necessary.
> 
>> The ratios (in %) are tracked as recent trends over ten, sixty, and
>> three hundred second windows, which gives insight into short term
>> events as well as medium and long term trends.

Good catch! So the docs *do* mention it, but of course I only grepped
for "percent" ... :)

> 
> also did i quick check here on my machine (by compiling pbs):
> 
>> ==> /proc/pressure/cpu <==
>> some avg10=10.63 avg60=3.66 avg300=0.87 total=54165853
> 
> so the `avg10=10.63` should be percent.
> 
> [1]: https://www.kernel.org/doc/html/latest/accounting/psi.html
> 
>>
>> [1/1] ui: RRD graphs: display PSI as percent
>>       commit: 2753e104a1e6effa4a0ae995f13636a02f3557af
>>
>>
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