Re: [PATCH v9 0/2] drm/xe/pmu: Enable PMU interface

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

On Fri, Jun 21, 2024 at 09:59:11AM +0530, Aravind Iddamsetty wrote:
>
>On 21/06/24 00:45, Umesh Nerlige Ramappa wrote:
>> On Fri, Jun 14, 2024 at 08:34:30AM -0700, Dixit, Ashutosh wrote:
>>> On Thu, 13 Jun 2024 22:50:39 -0700, Riana Tauro wrote:
>>>>
>>>> Hi Ashutosh
>>>>
>>>> On 6/14/2024 12:09 AM, Dixit, Ashutosh wrote:
>>>> > On Thu, 13 Jun 2024 03:04:09 -0700, Riana Tauro wrote:
>>>> >>
>>>> >
>>>> > Hi Riana,
>>>> >
>>>> >> There are a set of engine group busyness counters provided by HW which are
>>>> >> perfect fit to be exposed via PMU perf events.
>>>> >>
>>>> >> BSPEC: 46559, 46560, 46722, 46729, 52071, 71028
>>>> >>
>>>> >> events can be listed using:
>>>> >> perf list
>>>> >>    xe_0000_03_00.0/any-engine-group-busy-gt0/         [Kernel PMU event]
>>>> >>    xe_0000_03_00.0/copy-group-busy-gt0/               [Kernel PMU event]
>>>> >>    xe_0000_03_00.0/media-group-busy-gt0/              [Kernel PMU event]
>>>> >>    xe_0000_03_00.0/render-group-busy-gt0/             [Kernel PMU event]
>>>> >
>>>> > PMU patches merged previously were dropped in 90a8b23f9b85 ("drm/xe/pmu:
>>>> > Remove PMU from Xe till uapi is finalized") because PMU uapi was expected
>>>> > to change. Why are we re-posting these old patches again now, without
>>>> > including the planned uapi changes?
>>>>
>>>> The uapi changes were dropped and there are no other upcoming changes for
>>>> Group busyness. So re-posted the old series.
>>>
>>> What happened to VF busyness (which is why I thought the uapi was going to
>>> change)?
>>
>> There are no plans to support group busyness from a VF, so we are just exporting group busyness to maintain parity with i915 for Native/PF behavior. The only change would be to expose the counters in ticks rather than ns. I still have to look at this series to see if that's happening.
>
>how will the counter ticks be used to get the busyness in time

There will be no concept of "busyness in time units". User would just 
take 2 samples and calculate busyness as a percentage. The counters will 
be unitless. More info on equation here:
https://spec.oneapi.io/level-zero/1.9.3/sysman/api.html#_CPPv418zes_engine_stats_t

Percent utilization is calculated by taking two snapshots (s1, s2) and 
using the equation:

util = (s2.activeTime - s1.activeTime) / (s2.timestamp - s1.timestamp)

Note that zesEngineGetActivity is used to get single as well as group 
engine busyness from the KMD.

For single engine busyness, KMD will get the information from GuC and 
that would be a pair of counters - ActiveTicks and TotalActiveTicks 
corresponding to activeTime and timestamp in the above equation.

For group engine busyness, we should follow the same semantics.

Regards,
Umesh

>
>Regards,
>Aravind.
>>
>> Regards,
>> Umesh
>>>
>>>>
>>>> Thanks,
>>>> Riana
>>>> >
>>>> > Thanks.
>>>> > --
>>>> > Ashutosh