Fw: Introducing power performance counter contacts

[Maynard Johnson]

Maynard Johnson wrote:
I've read through the SystemTap documentation a couple of times, trying 
to absorb the concepts as best I can.  I have a few thoughts.  Go ahead 
and throw fireballs back at me if I misconstrue anything -- which I'm 
sure I will since I've probably just skimmed the surface of what you 
folks have been doing.

The ProfileTapset.txt file was of great interest to me as it seems the 
intent is to provide a generalized, cross-platform mechanism for 
interfacing with arbitrary PMUs that could be used by various existing 
(and future) performance tools.  However, it seems to me there's a 
fundamental mismatch between SystemTap and performance tools; i.e., 
SystemTap seems geared towards more of an adhoc usage model whereas 
(existing) performance tools API requirements are well-known.

In one section of the ProfileTapset document, there was mention of the 
current activity involving a possible merge of Perfmon and PerfCtr with 
the intent of getting a generalized PMU interface into the mainline 
kernel.  It's not clear to me whether this SystemTap/Profiling project 
would somehow build on that interface or replace it.  Could someone 
clarify the intent?

In the same section of the document, it's stated that "both pmu 
libraries [perfmon and perfctr] are geared more for user->kernel access 
rather than kernel->kernel access and we will need to see what can be 
EXPORT()'ed to make it more kernel module friendly".  Does this imply 
that all the knowledge of how to program the PMUs would be pushed down 
into the kernel with a SystemTap solution?  If so, there would need to 
be a way for performance tools to obtain that knowledge to present to 
the user all of the arch-specific events and profiling options.

I'm sure I'll have more questions as I digest the information and get 
more details from you all.

Thanks.
Maynard

>
>Maynard Johnson
>LTC Power Linux Toolchain
>507-253-2650
>
>----- Forwarded by Maynard Johnson/Rochester/IBM on 06/30/2005 04:32 PM
>-----
>                                                                           
>             prasadav@us.ltcfw                                             
>             d.linux.ibm.com                                               
>                                                                        To 
>             06/30/2005 10:23          "Chen, Brad" <brad.chen@intel.com>, 
>             AM                        "Spirakis, Charles"                 
>                                       <charles.spirakis@intel.com>,       
>                                       William Cohen <wcohen@redhat.com>,  
>                                       dwg@au1.ibm.com, Maynard            
>                                       Johnson/Rochester/IBM@IBMUS,        
>                                       Jeffrey Scheel/Rochester/IBM@IBMUS, 
>                                       Bill Buros/Austin/IBM@IBMUS         
>                                                                        cc 
>                                       Geoff Smith/Beaverton/IBM@IBMUS,    
>                                       SystemTAP                           
>                                       <systemtap@sources.redhat.com>      
>                                                                   Subject 
>                                       Introducing power performance       
>                                       counter contacts                    
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>I would like to Introduce
>Maynard Johnson:  He is the contact for PAPI, his area of expertise is
>mostly in the user space.
>David Gibson:  He is the main IBM contact for perfctr.
>Bill Buros: Lead for the performance team on Power platform.
>Jeff Scheel: He is the overall architect for Linux On Power.
>
>For the benefit of David/Maynard/Bill and Jeff, i will introduce others
>in the To list
>
>Will Cohen: He is the maintainer of Oprofile and he is heavily involved
>in SystemTAP.
>
>Brad Chen: He is the overall lead from Intel in the SystemTAP project.
>
>Charles Spirakis: Charles is looking at the performance counter issue
>along with Will in the systemtap project, charles has experience with
>vtune project.
>
>SystemTAP home page can be found at http://sourceware.org/systemtap/
>The home page has links to the mailing lists and all the other project
>related documents.
>
>Please let me know if i can be of any more help for all of you to make
>progress on the performance counters work.
>
>Thanks,
>Vara Prasad
>
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