On Tue, May 24, 2011 at 10:46:02AM +0200, Igor Stasenko wrote:
No mistake, the performance problem was real.
Good news - I found the cause. Better news - this may be good for a performance boost on StackVM and possibly Cog also.
The performance hit was due almost entirely to InterpreterPrimitives>>failed, and perhaps a little bit to #successful and #success: also.
This issue with #failed is due to "^primFailCode ~= 0" which, for purposes of C translation, can be recoded as "^primFailCode" with an override in the simulator as "^primFailCode ~= 0". This produces a significant speed improvement, at least as fast as for the original interpreter implementation using successFlag.
I expect that the same change applied to StackInterpreter may give a similar 10% improvement (though I have not tried it). I don't know what to expect with Cog, but it may give a boost there as well.
Changes attached, also included in VMMaker-dtl.237 on SqueakSource.
Dave
Thanks Igor.
it is strange that such small detail could make a lot of difference in speed.
Yes, I was very surprised to see it also. It will be interesting to see if it has a similar effect for StackInterpreter. I probably will not have time to check this for a while, so if you try it please let us know what you find.
Dave