[PATCH 12/12] accel/ivpu: Share NPU busy time in sysfs

[Tvrtko Ursulin]

On 13/05/2024 11:22, Jacek Lawrynowicz wrote:
> Hi,
> 
> On 10.05.2024 18:55, Jeffrey Hugo wrote:
>> On 5/8/2024 7:29 AM, Jacek Lawrynowicz wrote:
>>> From: Tomasz Rusinowicz <tomasz.rusinowicz at intel.com>
>>>
>>> The driver tracks the time spent by NPU executing jobs
>>> and shares it through sysfs `npu_busy_time_us` file.
>>> It can be then used by user space applications to monitor device
>>> utilization.
>>>
>>> NPU is considered 'busy' starting with a first job submitted
>>> to firmware and ending when there is no more jobs pending/executing.
>>>
>>> Signed-off-by: Tomasz Rusinowicz <tomasz.rusinowicz at intel.com>
>>> Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz at linux.intel.com>
>>
>> This feels like something that would normally be handled by perf. Why not use that mechanism?
> 
> Yeah, probably but we had several request to provide easy to use interface for this metric that
> could be integrated in various user space apps/tools that do not use ftrace.

Probably more Perf/PMU aka performance counters? Which would be 
scriptable via $kernel/tools/perf or directly via perf_event_open(2) and 
read(2).

Note it is not easy to get right and in the i915 implementation (see 
i915_pmu.c) we have a known issue with PCI hot unplug and use after free 
which needs input from perf core folks.

Regards,

Tvrtko