[Python-Dev] Drop the new time.wallclock() function? (original) (raw)

Christian Tismer tismer at stackless.com
Wed Mar 14 06:24:20 CET 2012

The performancecounter is a thing that typically gets intercepted by the VM infrastructure and does no longer work as a reliable timing source. In PyPy there are tests which check certain assumptions how much the performancecounter must advance at least between a few opcodes, and that does not work in a VM.

cheers - Chris

On 3/13/12 6:11 PM, Kristján Valur Jónsson wrote:

Interesting thought. Althougn I don't see how that could fail on windows, if the QPC function is really just talking to a clock chip, surely that hasn't been virtualized. Is there an actual example of windows hardware where this api fails (virtual or not?) Perhaps there is no real need to have a fallback mechanism, and it would even be best to write such a mechanism inside the function itself, and just return getsystemtimeasfiletime() instead.

K -----Original Message----- From: Christian Tismer [mailto:tismer at stackless.com] Sent: 13. mars 2012 18:07 To: Kristján Valur Jónsson Cc: Guido van Rossum; Victor Stinner; Python Dev Subject: Re: [Python-Dev] Drop the new time.wallclock() function? Btw., have you considered virtual machines? I happen to run windows in Parallels or Virtualbox quite often. There the "wall clock" stuff notoriously does not work. It would be good (but difficult?) if the supposed-to-be-accurate clock could test itself, if it works at all, and replace itself with a fallback. In my case, this causes quite a few PyPy tests to fail ;-) ciao -- Chris

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