[Issue 3742] Please add support for 'Lightweight Profiling' which adds a set of user-controlled counters to the AMD64 architecture

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3742


Don <clugdbug at yahoo.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |clugdbug at yahoo.com.au


--- Comment #3 from Don <clugdbug at yahoo.com.au> 2010-02-04 06:44:53 PST ---
I'm not sure that this is terribly relevant to D.
For in-depth analysis, this feature is nowhere near as comprehensive as the
hardware performance counters which have existed since the Pentium MMX days
(and which seem very under-utilized -- they are really fantastic). I think AMD
is being deliberately misleading. I take offence to this section:
"These counters are used by the AMD CodeAnalyst Performance Analyzer and
provide deep insight into application
and system performance. However, each time a data sample is gathered, the
processor must take an interrupt to a kernel-mode driver, and that takes
hundreds or thousands of cycles."

It *sounds* as though this is talking about the hardware performance counters.
But it ISNT!! It's talking about their "performance analyzer". It is possible
to get the same data they're talking about, without calling into kernel mode
all the time. You do NOT need to use their driver.

So, it's maybe a 5-10% improvement over what already exists. May be useful for
JIT compilers, but it isn't really anything to get terribly excited about.

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