I think that in order to fix the memory usage issues, we may need to
adjust the number of unified sources at a per-directory level. For
example, I would expect the compiler to consume more memory compiling
more C++ feature heavy code such as the typical JS engine source code
than the average Gecko code. Therefore I'm more interested to see
people file bugs about specific memory usage problems that we can
address on a more granular level. I don't think that decreasing this
number across the tree will buy us anything significant.
Cheers,
Ehsan
On 12/2/2013, 11:39 PM, Mike Hommey wrote:
Hi,
It was already mentioned that unified builds might be causing memory
issues. Since the number of unified sources (16) was decided more or
less arbitrarily (in fact, it's just using whatever was used for
ipdl/webidl builds, which, in turn just used whatever seemed a good
tradeoff between clobber build and incremental build with a single .cpp
changing), it would be good to make an informed decision about the
number of unified sources.
So, now that mozilla-inbound (finally) builds with different numbers of
unified sources (after fixing bugs 944844 and 945563, but how long
before another problem slips in?[1]), I got some build time numbers on my
machine (linux, old i7, 16GB RAM) to give some perspective:
Current setup (16):
real 11m7.986s
user 63m48.075s
sys 3m24.677s
Size of the objdir: 3.4GiB
Size of libxul.so: 455MB
12 unified sources (requires additional patches for yet-to-be-filed bugs
(yes, plural)):
real 11m18.572s
user 65m24.145s
sys 3m28.113s
Size of the objdir: 3.5GiB
Size of libxul.so: 464MB
8 unified sources:
real 11m47.825s
user 68m21.888s
sys 3m39.406s
Size of the objdir: 3.6GiB
Size of libxul.so: 476MB
4 unified sources:
real 12m52.630s
user 76m41.208s
sys 4m2.783s
Size of the objdir: 3.9GiB
Size of libxul.so: 509MB
2 unified sources:
real 14m59.050s
user 90m44.928s
sys 4m45.418s
Size of the objdir: 4.3GiB
Size of libxul.so: 561MB
disabled unified sources:
real 18m1.001s
user 113m0.524s
sys 5m57.970s
Size of the objdir: 4.9GiB
Size of libxul.so: 628MB
Mike
1. By the way, those type of bugs that show up at different number of
unified sources are existing type of problems waiting to arise when we
add source files, and running non-unified builds doesn't catch them.
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