New submission from Χρήστος Γεωργίου (Christos Georgiou):
(related to issue #24915)
I discovered that `make profile-opt` does not use the profile information for
the builtin-modules (e.g. arraymodule or _pickle) because in the `profile-opt`
target there is the following sequence of actions:
…
$(MAKE) build_all_merge_profile
@echo "Rebuilding with profile guided optimizations:"
$(MAKE) clean
$(MAKE) build_all_use_profile
…
The action `$(MAKE) clean` performs an `rm -rf build`, destroying among other
things all the *.gcda files generated for the built-in modules.
On my Linux system with gcc, a kludge to `Makefile.pre.in` that works is:
…
@echo "Rebuilding with profile guided optimizations:"
find build -name \*.gcda -print | cpio -o >_modules.gcda.cpio # XXX
$(MAKE) clean
cpio -id <_modules.gcda.cpio # XXX
$(MAKE) build_all_use_profile
…
but, like I said, it's a kludge and it's POSIX-only (-print0 can be avoided
since I believe it's guaranteed that there will be no
whitespace-containing-filenames).
Now, if this road is to be taken, I believe the most cross-platform method
available to save the profile-generated files is to use a custom python script
(at this point, the local profile-generating python executable is functional)
and make a tar file, which will be untared back. However, I don't like it much.
I'm willing to provide any necessary patches if someone gives me a "proper"
roadmap as to how to handle this issue.
----------
components: Build
messages: 259842
nosy: tzot
priority: normal
severity: normal
status: open
title: no PGO for built-in modules with `make profile-opt`
type: performance
versions: Python 2.7, Python 3.5, Python 3.6
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Python tracker <[email protected]>
<http://bugs.python.org/issue26307>
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