[cfe-dev] Clang executable sizes and build stats

[Greg Bedwell via cfe-dev]

Thanks for raising this. This is something we've recently been looking at
too at Sony, as over the course of PS4's lifetime so far we've seen our
clang executable on Windows approximately double in size, which isn't ideal
for things like distributed build systems.  A graph of clang.exe size on
our internal staging branch matches yours closely with it being more of a
death by a thousand cuts rather than being down to a small number of sudden
big-bang changes.

I did spot one range of about 25 upstream commits in our data where the exe
size increased by over 1MB. My prime suspect in that range was a new
scheduling model being added to the X86 backend but I've not bisected
further to be sure yet.  This would be an interesting case for us as we
don't really need to support any models other than Jaguar for our users but
don't want to break the LLVM tests, nor introduce loads of private changes
to our branch.

I know our test/QA team have been doing some analysis using Bloaty
McBloatFace to see exactly where the size is coming from and produced some
really nice visualizations of that data.  They've also been looking at how
the MinSizeRelease config does on Windows. I think the size savings were
decent but I'm not sure of performance numbers, if they have any yet.

I'll ask around at what we have to share once back in the office.

Thanks for sharing your data!

-Greg



On Sat, 17 Mar 2018 at 12:36, Dimitry Andric via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi all,
>
> I recently did a run where I built clang executables on FreeBSD 12-CURRENT
> [1], from trunk r250000 (2015-10-11) all through r327700 (2018-03-16), with
> increments of 100 revisions.  This is mainly meant as an archive, for
> easily doing bisections, but there are also some interesting statistics.
>
> From r250000 through r327700:
> * the total (stripped) executable size grew by approximately 43%
> * the size of the text segment grew by approximately 41%
> * the size of the data segment grew by approximately 61%
> * the size of the bss segment grew by approximately 185%
> * real build time (on a 32 core system) grew by approximately 60%
> * user build time (on a 32 core system) grew by approximately 62%
> * maximum resident set size (RSS) grew by approximately 32%
>
> Google spreadsheet with more numbers and some graphs:
>
>
> https://docs.google.com/spreadsheets/d/e/2PACX-1vSGq1U7j45JNC_bcG4HV3jKOV4WBUPbTSgMMFXd5SD0IEPTAFwWnlU2ysprmnHsNe5WONRCjg8F5mHK/pubhtml
>
> -Dimitry
>
> [1] These were built using the "ninja clang clang-headers" target,
> followed by "ninja install-clang install-clang-headers".
>
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