linux-kernel - Re: PMC support for ARMv6

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Date:	Thu, 15 Jan 2009 15:32:28 -0500
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	Gaurav Singh <gausinghnsit@...il.com>
Cc:	ltt-dev@...ts.casi.polymtl.ca, linux-kernel@...r.kernel.org
Subject: Re: PMC support for ARMv6

* Gaurav Singh (gausinghnsit@...il.com) wrote:
> Hi Mathieu / all,
> I have integrated PMC in ARMv6 primarily for 2 aims:
> 1. CPI calculations - this trace_mark is triggered triggered after X no. of
> clock cycles. The number of instructions executed and the no. of clock
> cycles is noted.
> 2. Cache Hit rate calculation - Here I have not used the PMC registers in
> the ARM processor - rather have used L2 Cache controller  registers to find
> out this information - but this does not provide information about the L1
> cache hit/miss behaviour.
> 
> Any other suggestions on what else can be done in PMC?
> 

I'd like to see this trace_mark turned into a tracepoint probe. Having a
periodical interrupt which saves this information is good, but I would
also like to have a tracepoint probe that we could attach at important
execution sites, like sched change, irq, softirq, nmi entry/exit where
we would read the performance counter.


> Also have ported LTTng to 2.6.24 for two Nomadik Boards - NDK15 and
> NDK20. Doing some tests and will send it over to you guys soon for your
> comments.
> 

I'd be interested in merging your patchesfor 2.6.28 into the LTTng tree.
Please keep us posted.

Mathieu

> Cheers!
> Have a Nice Day!
> Gaurav

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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