https://bugs.freedesktop.org/show_bug.cgi?id=42949
Bug #: 42949
Summary: EasyHack: accelerating compile times ...
Classification: Unclassified
Product: LibreOffice
Version: unspecified
Platform: Other
OS/Version: All
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Libreoffice
AssignedTo: [email protected]
ReportedBy: [email protected]
One of our problems is that compile times are too slow; part of the reason for
this is header explosion - such that we parse and compile the same things again
and again for each module. If we can identify headers that are included
un-necessarily many times, then we should be able to accelerate the build for
everyone.
After a build - we have full library dependencies in .d files, such that:
cat workdir/unxlngi6.pro/Dep/LinkTarget/Library/*.d | grep '^ ' | sed
's/\\.*//' | sort | uniq -c | sort -n > /tmp/headers.includes
for a in `cat /tmp/headers.includes`; do if test -f /opt/libreoffice/core/$a;
then wc -c $a; else echo -n "$a "; fi; done > /tmp/headers.csv
ONO. should give us a /tmp/headers.csv that has the size and include count of
each header in the build [ presumably a faster, perl tool could be used to
generate this ;-].
By multiplying these, we can get an estimate of the 'weight' that a header
provides to the build; hence:
bytes to parse include count size filename
741439564 4454 166466
/opt/libreoffice/core/solver/unxlngi6.pro/inc/boost/preprocessor/seq/fold_left.hpp
416181480 6754 61620
/opt/libreoffice/core/solver/unxlngi6.pro/inc/rtl/ustring.hxx
Shows we parse 740Mb of the same file over 4000 includes - for the set of files
I grokked. I up-loaded a spreadsheet here:
http://users.freedesktop.org/~michael/headers.ods - but the include counts look
suspiciously low here.
Anyhow - having found our problem headers; we then need to work out how we can
reduce their use - preferably by finding out where such headers are included
from, and how to reduce their use [ by adding class Foo; forward definitions
eg. ].
Clearly that's not going to work for eg. the string classes which are used
everywhere, but quite possibly we can reduce the boost/ related wasteage, as
well as help to identify future areas for improvement (eg. aggregating
OutputDevice from Window, rather than including it :-)
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