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Those are redundant, and yaml parser strips them in fact. By removing them, loading and saving yaml file without any change indeed produce the same output. This is useful for prepare_for_translation.py script (which adds lang and ref tags) - to produce only change that indeed was made.
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| lang | layout | permalink | redirect_from | ref | title | |||
|---|---|---|---|---|---|---|---|---|
| en | doc | /doc/profiling/ |
|
48 | Python Profiling |
This is a python profiling primer.
For the purpose of this document, qubes-dev is name of the domain used for postprocessing profiling stats.
Requirements
yum install gprof2dot graphviz
git clone http://git.woju.eu/qubes/profiling.git
If you profile something in dom0, move Upload.sh from the repository to dom0:
mkdir -p ~/profiling
qvm-run -p qubes-dev 'cat ~/profiling/Upload.sh' > ~/profiling/Upload.sh
- WARNING: this will obviously be running third-party code which is not signed by ITL nor Fedora. You have been warned.
Workflow
Identify function responsible for some slow action
You have to select the area in which you suspect less than optimal performance. If you do not narrow the area, graphs may be unreadable.
Replace suspect function with probe
Replace
def foo(self, bar):
# function content
with
def foo(self, *args, **kwargs):
profile.runctx('self.real_foo(*args, **kwargs)', globals(), locals(),
time.strftime('/home/user/profiling/foo-%Y%m%d-%H%M%S.pstats'))
def real_foo(self, bar):
# function content
Run application
Beware that some functions may be called often. For example qubesmanager/main.py:update_table gets run once per second. This will produce one pstat file per second.
Remember to revert your changes to the application afterwards.
Upload statistics
If you are in dom0:
cd ~/profiling
./Upload.sh
Analyse
make
For every ${basename}.pstats this will produce ${basename}.txt and ${basename}.svg. SVG files contain call graphs. Text files contain lists of all functions, sorted by cumulative execution time. You may also try make all-png.
make index.html
This creates index.html with all SVG graphics linked to TXT files, ready for upload.
make REMOTE=example.com:public_html/qubes/profiling/ upload
Example
This example is from qubes-manager (qubesmanager/main.py).
It is apparent that the problem is around get_disk_usage, which calls something via subprocess.call. It does this 15 times, probably once per VM.