WPA stream_out form & memory consumption

[Martin Liška]

On 03/25/2014 09:50 PM, Jan Hubicka wrote:
>> Hello,
>>     I've been compiling Chromium with LTO and I noticed that WPA
>> stream_out forks and do parallel:
>> http://gcc.gnu.org/ml/gcc-patches/2013-11/msg02621.html.
>>
>> I am unable to fit in 16GB memory: ld uses about 8GB and lto1 about
>> 6GB. When WPA start to fork, memory consumption increases so that
>> lto1 is killed. I would appreciate an --param option to disable this
>> WPA fork. The number of forks is taken from build system (-flto=9)
>> which is fine for ltrans phase, because LD releases aforementioned
>> 8GB.
>>
>> What do you think about that?
> I can take a look - our measurements suggested that the WPA memory will
> be later dominated by ltrans.  Perhaps Chromium does something that makes
> WPA to explode that would be interesting to analyze.  I did not managed
> to get through Chromium LTO build process recently (ninja builds are not
> my friends), can you send me the instructions?
>
> Honza
>> Thanks,
>> Martin

There are instructions how can one build chromium with LTO:
1) install depot-tools and export PATH variable according to guide: 
http://www.chromium.org/developers/how-tos/install-depot-tools
2) Checkout source code: gclient sync; cd src
3) Apply patch (enables system gold linker and disables LTO for a 
sandbox that uses top-level asm)
4) which ld should point to ld.gold
5) unsure that ld.bfd points to ld.bfd
6) run: build/gyp_chromium -Dwerror=
7) ninja -C out/Release chrome -jX

If there are any problems, follow: 
https://code.google.com/p/chromium/wiki/LinuxBuildInstructions

Martin

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