Re: [PATCH] perf_counter: extensible perf_counter_attr

Corey Ashford
2009-06-10T22:07:15Z

Paul Mackerras wrote:
> Corey Ashford writes:
>
>> Ok, some disclosure here: we have not yet supported either of these features in
>> the Power PMU's in any open source code (and perhaps the proprietary code too,
>> but I don't know about that). Since these features are described in an IBM
>> proprietary document, I can't describe how they work here, except to say that
>> they are present in the chip.
>
> Actually, the public PPC970FX user manual has a chapter on the
> performance monitor unit which describes both thresholding and the
> instruction matching CAM, among other things.

Ah, good point!

Anyone interested can find the 970FX (G5) manual here: www.cs.lth.se/EDA116/G5.pdf
It's supposed to be on the IBM web site too, but for some reason, the link is
broken (reported!).

>
> I think we can support thresholding using higher-order bits of the
> event code when the low bits == PM_THRESH_TIMEO. We can only have one
> PM_THRESH_TIMEO event on the PMU at any given time, so there can't be
> any conflict over the thresholder settings.
>
> The IMC is more problematic, but we can't do much with it on POWER5
> and later processors anyway, due to various things being accessible
> only in hypervisor mode, so I have been ignoring it. :)
>
> Paul.

Ug. Well, there's always bare-metal Linux :)

- Corey