Re: [RFC 0/6] Non perf based Gen Graphics OA unit driver
From: Peter Zijlstra
Date: Fri Oct 16 2015 - 06:33:58 EST
On Fri, Oct 16, 2015 at 12:02:28PM +0200, Ingo Molnar wrote:
>
> * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> > > - We may be making some technical compromises a.t.m for the sake of
> > > using perf.
> > >
> > > perf_event_open() requires events to either relate to a pid or a
> > > specific cpu core, while our device pmu relates to neither. Events
> > > opened with a pid will be automatically enabled/disabled according
> > > to the scheduling of that process - so not appropriate for us.
> >
> > Right; the traditional cpu/pid mapping doesn't work well for devices;
> > but maybe, with some work, we can create something like that
> > global/local render context from it; although I've no clue what form
> > that would need at this time.
>
> Could someone please help with some very basic questions, such as what the
> hardware model of the 'OA' unit model is? How are OA registers set up, how are
> their values made accessible to the host side, etc.
Robert linked to:
https://01.org/sites/default/files/documentation/observability_performance_counters_haswell.pdf
In a previous posting. It has some info, but full documentation, is as
per the initial post, 'pending'.
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