I find Python's startup time to be very sluggish. I wish it was less than 50 milliseconds (0.05 seconds) including running hg, which is the common threshold for "instant". On my machine 'python -c ""' takes about 0.05 seconds but 'python3 -c ""' takes 0.125 seconds. I will be very happy to see any speedup.
On Tue, Apr 15, 2014 at 11:34 AM, Skip Montanaro <s...@pobox.com> wrote: > 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 > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/dholth%40gmail.com _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
