Eric wrote:
> Perhaps not so much "a very real advantage" as "less of a
> distraction". It's still significantly slower than 2.7. :)
I'm still confused. I peeked in /usr/bin/hg. The only "system" modules
it imports directly are os and system (maybe I'm using an ancient
version?). After that, it imports its own lazy import module. This
suggests to me that Mercurial's import slowness is mostly in its own
code (I counted 104 Python modules and six shared objects in its
mercurial package, which isn't going to be affected (much?) by
freezing the Python standard modules.
I'm not trying to be difficult here. I thought that way back in the
day a huge amount of work was done to remove needless filesystem
activity, and zip packaging has been around for quite awhile.
As an experiment, I ran hg pull as
/usr/bin/python -v /usr/bin/hg pull
in my cpython repo then looked at the -v output. Summarizing the
output I saw the following:
30 imports (0 dlopens)
Python banner printed
86 imports (18 dlopens)
adding changesets message
5 imports (2 dlopens)
adding manifests message
1 import (0 dlopens)
adding file changes message
7 imports (3 dlopens)
added ... changesets message
4 imports (0 dlopens)
run 'hg update' message
(I missed a "searching" message in there somewhere.)
That's a total of 133 imports, 23 of which were satisfied by loading
an extension module. The imports break down as follows:
51 imports (4 dlopens) from the mercurial package
5 imports from the hgext package
7 imports from the encodings package
Everything else is imported from the top level, and at a glance
appears to be all Python stdlib stuff. The key period of execution
looks to be between the printing of the Python banner and the printing
of the adding changesets message. I see 46 imports (2 dlopens) from
the mercurial or hgext packages. That leaves 40 stdlib imports, of
which 16 were satisfied by dlopen.
As a final check, I saved all the stdlib import statements from the -v
output (77 statements) to a file and timed its execution:
% time /usr/bin/python ~/tmp/pyimp.py
real 0m0.162s
user 0m0.034s
sys 0m0.010s
It doesn't take much time to import every stdlib module that Mercurial
needs. I don't know how much slower all this import machinery is in
3.x (and can't test at work, as we don't have a copy laying about). It
would probably have to be 3x or more slower for it to have much
visible impact on even simple hg commands. I find it hard to believe
that freezing the stdlib is going to lower the barrier enough for the
Mercurial folks, if, in fact, import slowness is their main reason for
not moving to 3.x.
Skip
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