Re: libstdc++-v3 PATCH: STL configuration change

[Benjamin Kosnik <bkoz at redhat dot com>]

Loren, thanks for your excellent and very detailed work. I would appreciate 
it if you'd add links to your last message and initial performance 
analysis in the faq/howtos.

Please check this patch in, to both trunk and branch.

I'd love it if some kind of regression went it to test this stuff, but 
I'm not quite sure how to do this. 

We really need to think of a new catagory of testsuite cases, that test 
for memory leaks (the string memory issue comes immediately to mind as 
another test case in this category). 

It would also be nice to have some kind of automated 
way where performance analysis could be done as part of running the 
testsuite. The old mkcheck script did this a bit, by measuring runtime 
speed. I suppose if we looped  critical blocks we could even measure 
performance differences. (Of course there's an endless hole here of 
cache, avoiding cache, etc.)

Still, I'd like people to try and set up a framework for tests of this 
kind. I think it's really important, especially as more people work on tuning 
libstdc++-v3, that some kind of non-hand-wavy, explicit and quantative 
method is in place for measuring performance claims. A place to start 
might be some of the bench++ work, and seeing if those measurement 
techniques can be brought over to the libstdc++-v3 testsuite.

best,
benjamin