Re: [PATCH v2 1/7] drm/i915/perf: rework aging tail workaround

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On 19/02/2019 09:18, Chris Wilson wrote:
Quoting Lionel Landwerlin (2019-02-18 18:35:28)
We're about to introduce an options to open the perf stream, giving
the user ability to configure how often it wants the kernel to poll
the OA registers for available data.

Right now the workaround against the OA tail pointer race condition
requires at least twice the internal kernel polling timer to make any
data available.
I think this code is bogus. I do not think there is an aging problem on
hsw+, the only cause of zeroes being written that I've found is from
changing configs.
-Chris


Hmm... I'm pretty sure there is an issue and it's actually worse on the HSW machine I have than on later machines.

The DRM_NOTE in that function is appearing a lot more on HSW.


Yes, there is also an issue with how long it takes to reprogram the GPU.


-Lionel

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