Comment #1 on issue 2053 by [email protected]: Unexpected
performance varaiations on physics simulation
http://code.google.com/p/v8/issues/detail?id=2053
I'm the author of the Chromium bug report 121196.
I do not yet have good profile data to make any good interpretation of the
following results I get in Chrome ... but I am normally seeing the model
itself running at 550-600 model-steps/s. When Chrome is running slowly the
rate drops to 120-150 ... however during one test on Windows 7 (on the same
machine) I got a measurement of 1724 model-steps/s.
It would be nice to get that performance regularly!
I'd like to know how to get detailed profiling information when running our
physics simulation in Chrome ... but for now to get further I have
installed v8 locally and extracted the part of our code running just the
molecular dynamics simulation so I can run it with d8 and get better
profiling data started this thread on the v8-users list (no responses yet):
how to interpret the output when running with --trac-deopt on?
http://groups.google.com/group/v8-users/browse_thread/thread/14c339abe646c6c5#
I've created instructions on building v8 and running just the molecular
dynamics engine with d8 with various profiling flags turned on:
https://gist.github.com/2289269
I do not yet know if the data I am collecting using d8 also shows the same
kind of huge variation in speeds we are seeing in Chrome -- but is it
already clear that something is causing the main integration function to be
deoptimized over and over:
makeIntegrator.integrate()
See the profile.log here: https://raw.github.com/gist/2289269/profiling.log
Information below is for reference for other developers I point to this bug
report:
For more info on interpreting the results see Florian Loitsch's series on
profiling and optimizing code for V8 starting with this post:
http://floitsch.blogspot.com/2012/03/optimizing-for-v8-introduction.html
I'm still trying to understand what is causing the deoptimization ...
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