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RE: [perfmon] Re: perfmon2 TODO list (4/4)
- From: "Stone, Joshua I" <joshua dot i dot stone at intel dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: <systemtap at sources dot redhat dot com>, <perfmon at napali dot hpl dot hp dot com>, "Stephane Eranian" <eranian at hpl dot hp dot com>
- Date: Thu, 13 Apr 2006 14:21:45 -0700
- Subject: RE: [perfmon] Re: perfmon2 TODO list (4/4)
Frank Ch. Eigler wrote:
>>>> Some options to get context setup:
>>>> -generate bit patterns when compiling systemtap script
>>>> and generate static array with information for context,
>>>> pmc, and pmd setup.
>
> This is what we hope to do. That means that we only would need the
> low-level register manipulation API in the kernel, and not the
> abstract event naming, configuration/compatibility checking, etc.
> [...]
> That is correct. During systemtap script compilation, the event names
> would be translated to low level PMU register configurations.
We need to be careful for the case of pre-compiled or cross-compiled
modules. If all of the translation and checks happen at compile time,
then we'll need to make sure at init time whether we're still on a
compatible cpu.
If we can delay this until runtime, it could still be managed in
user-mode via the stpd daemon, and we'd be guaranteed that the PMU
values match the current CPU.
Josh