I'm maybe a scandalmonguer, but the only big structural change is the template 
feature. If you process only one file, the penality is a lot bigger : 10 times 
slower in my tests.

From Emmanuel at txt2tags-dev:

Benchmarks are also difficult :) I have only a one third penalty (from
2.6) on my tests. Which is not good but not so bad.

And a quick (git) bisect leads to the following:
About half of the increasing is added by r525 (remote files). The
remaining part culprit is not so obvious.
There's probably many culprits :)

Seeing r525 now, the only significant change to the txt2tags code was:

import urllib
...
f = urllib.urlopen(file_path)

Is urllib that slow? Maybe we'll need a profile tool to point exactly where the 
delay is.

Python does come with a basic profiler:
http://docs.python.org/library/profile.html

I did just a quick run with it with both 2.6 and svn versions converting 
sample.t2t -t html. Not at all a proper profiling test, but it gets the start 
of an idea. The run shows that the biggest difference in time is in loading 
additional modules that were not loaded before. (urllib, urlparse, socket, 
utils, mimetools, ssl, tempfile) Just the loading of these modules took up 
nearly a third of the total running time.

The next biggest difference was in the use of regular expressions. This isn't 
surprising, as SVN does a lot more than 2.6 did, but it might be a place to 
look at for refactoring. Perhaps making sure all regexes are moved out of 
funtions that get called more than once (like the main regexes are now) so they 
do not get compiled each time. Otherwise, that only differences I can see from 
a cursory scan is that more functions are called, particular string and list 
manipulation methods, but that is difficult to refactor away.

Thanks Jason,

this is really interesting. In particular the module loading penalty would 
explain the gap I got at r525. But this is probably the price to pay for these 
interesting new features...

Thank you VERY much for all this information Jason!

I didn't know that the urllib module would carry all those extra modules. I'll 
try to do the urllib import just when needed.

About regexes, from my head I don't think many of them were added since v2.6, 
but I'll investigate that.

Yeah, I said that about the regexes without actually checking, although I meant 
it more for general refactoring and not as something specifically introduced 
since 2.6. I have since checked, and only one function does this (parse_line in 
ConfigLines). I factored those out to the class definition, and it sped up the 
above test by ~7%. Not huge, but still an improvement.

Much bigger was loading urllib only when needed. I did that with the same 
commit, and it reduced the time almost by half! Of course, if it ever needs to 
get used it will slow things down, but I think that loading a remote file will 
be a much bigger difference than loading the module that makes it possible. The 
rest of the time, it is much better.

Oh, one more thing...

time for t in $targets; do txt2tags26 -q -t $t -i sample.t2t -o /tmp/x; done

real    0m10.309s
user    0m9.516s
sys 0m0.743s

# revision 606
time for t in $targets; do txt2tags -q -t $t -i sample.t2t -o /tmp/x; done

real    0m15.726s
user    0m14.616s
sys 0m1.053s

# revision 607, with speed refactoring:
time for t in $targets; do txt2tags -q -t $t -i sample.t2t -o /tmp/x; done

real    0m11.198s
user    0m10.259s
sys 0m0.880s

So I'm gonna guess that urllib was the biggest culprit for the slowdown.

Well done Aurélio and Jason ! And apology to Emmanuel for my wrong suspicion 
about the template patch.

Don't worry Florent, bisect made me sleep ok anyway.
By the way, I have some problem with the test suite. Is it my checkout or do 
you guys have also problems testing r607 with module headers?

Emmanuel, even if your template patch was the culprint, there's no problem! 
We're here to improve and fix txt2tags ad infinitum :) Maybe my initial comment 
was too harsh, but that wasn't the intention, sorry.

Jason, thank you VERY much for your patch, bringing txt2tags back to the fast 
lane! Just like Emmanuel, now I'll sleep ok too :)

Now talking about r607:

Newbie question: there's performance gain in doing "from foo import bar; bar()" 
instead "import bar; foo.bar()"?

I agree with you than when using remote files, the module loading time will be 
a minor issue since loading the file via http is already slow. Your solution is 
perfect.

I liked the moving of regexes to the class definition and posterior checking 
for target/keyword. It made the code more readable, thanks! I just made two 
fixes in r608, and now the test-suite is 100% again.

Friendly reminder to all: always run dist/check-code.sh and test/run.py before 
a commit :)

In r609 the module 'email' was also postponed, giving us minor performance 
gains.
It's just used in a specific situation: using %%mtime inside a remote http file.

When I comment out all calls to Debug() performance improves quite a bit for 
the trunk version (r1096):


# With Debug()
time ./txt2tags -i userguide.t2t -o userguide.html -t xhtml 
real    0m0.713s
user    0m0.680s
sys 0m0.028s


# Without Debug()
time ./txt2tags -i userguide.t2t -o userguide.html -t xhtml 
real    0m0.643s
user    0m0.616s
sys 0m0.024s


This change almost brings the trunk version up to par with version 2.6 (r382):

time ./txt2tags -i userguide.t2t -o userguide.html -t xhtml
real    0m0.620s
user    0m0.596s
sys 0m0.020s


Do you think this warrants the removal of the Debug() calls?

BTW: A good way to search for culprits that are responsible for the code 
slowdown is the following:

python -m cProfile -o t2t.prof txt2tags -i userguide.t2t -o userguide.html -t 
xhtml 
runsnake t2t.prof