Date: Wed, 28 Jul 2010 05:06:50 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-amd64@freebsd.org Subject: Re: PERFMON isn't operational on amd64 Message-ID: <20100728044151.Y1330@delplex.bde.org> In-Reply-To: <201007270928.24959.jhb@freebsd.org> References: <AANLkTim3m4VX3sy6diTNna2Yb7i%2B4RQZ0kT6U7e_wqTU@mail.gmail.com> <201007270928.24959.jhb@freebsd.org>
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On Tue, 27 Jul 2010, John Baldwin wrote:
> On Tuesday, July 27, 2010 8:43:00 am pluknet wrote:
>> Hi.
>>
>> What is a status of "options PERFMON" on amd64?
>> ...
>> Looking at cvs I see amd64/include/perfmon.h was never here.
>
> PERFMON in general is obsoleted by hwpmc(4) which is far more useful and
> featureful. It should probably just be axed.
Nothing should just be axed.
hwpmc(4) is far too featureful for me, yet perfmon(4) still does things
for me that hwpmc cannot do:
- from userland, without using the library, try undocumented unnamed
counters. There are a few useful ones for k7. E.g.:
0xc8 (k8-fr-retired-near-returns) and
0xc9 (k8-fr-retired-near-returns-mispredicted)
are k8-only according to hwpmc and amd docs, but also work on my k7
(after a 4-line fix for perfmon on kx).
- in the kernel count, events at the level of individual functions, non-
statistically using high resolution kernel profiling. This may result
in more time spent counting than doing useful work, but provides
high resolution.
Bruce
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