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TSC support is broken. #12

Closed GoogleCodeExporter closed 8 years ago

GoogleCodeExporter commented 8 years ago 
Building with TSC (the WITH_TSC define, enabled by --with-tsc) which
instruments CPython with CPU counters, is currently broken (at least by the
vmgen patch, which does not include the right #ifdefs in call_function and
the CALL_FUNCTION_VAR_KW opcode implementation.)

Original issue reported on code.google.com by thomaswout@gmail.com on 14 Apr 2009 at 1:34

GoogleCodeExporter commented 8 years ago

Original comment by collinw on 29 May 2009 at 4:11

GoogleCodeExporter commented 8 years ago 
Reid's fixing this as he works on the instrumentation stuff.

Original comment by collinw on 1 Jun 2009 at 10:38

GoogleCodeExporter commented 8 years ago 
WITH_TSC is totally broken, it turns out.

First, it didn't work on x86_64.  That was why it kept segfaulting yesterday.

Second, the meaning of what it was trying to measure is now lost with 
FAST_DISPATCH
and computed gotos.  When the TSC stuff was originally written, it made the
assumption that control always made it back to the top of the main eval for 
loop, and
that assumption is quite wrong right now.  Furthermore, it tries to measure 
things
like loop overhead, which if you consider multiple FAST_DISPATCH'ed opcodes in 
a row
doesn't really make sense.

In order to make it work the way it used to, we'd have to insert code in the
beginning of the TARGET macro, which would probably hurt performance a lot, 
since it
prints to stderr every time it takes a measurement.

To me it seems like the right thing to do is to rip it out and do timings for 
what we
really care about, using the same old TSC flag.  We should also load the 
statistics
up in a vector or something instead of printing to stderr on every opcode 
(whose idea
was that?).

So what is it that we really want to profile?  Function call overhead seems 
like a
place to start, but should I anticipate trying to record information about 
other opcodes?

Original comment by reid.kle...@gmail.com on 2 Jun 2009 at 9:54

GoogleCodeExporter commented 8 years ago 
This issue was closed by r611.

Original comment by reid.kle...@gmail.com on 5 Jun 2009 at 7:08