Why not -parallelizeTargets ?

[Yuzo Fujishima]

To build Chromium for Mac from command line, 

$ xcodebuild -project all.xcodeproj -configuration Debug -target All

is recommended at http://code.google.com/p/chromium/wiki/MacBuildInstructions 

Are there any reasons not to use -parallelizeTargets option?

On my 2 quad-core CPUs machine, the option makes the build significantly faster,

without any noticeable issues.

Yuzo

[Thomas Van Lenten]

So the answer is it used to be that that setting simply overrode what was set in the project (when it was set to false).  We already have parallel targets turned on in the project. But the test below seems to indicate that might not be the case with Xcode 3.2.x.  I'll follow up with a radar to see why the settings in the project doesn't seem to be honored on command line like it is honored for IDE builds.

$ sw_vers 

ProductName: Mac OS X

ProductVersion: 10.6.4

BuildVersion: 10F569

$ sysctl -n hw.ncpu

4

$ rm -rf xcodebuild

$ time xcodebuild -project build/all.xcodeproj -configuration Debug -target All -nodistribute

...

real 51m39.726s

user 126m7.482s

sys 26m58.144s

$ rm -rf xcodebuild

$ time xcodebuild -project build/all.xcodeproj -configuration Debug -target All -nodistribute -parallelizeTargets

...

real 43m17.513s

user 126m56.996s

sys 26m57.332s

TVL

 

Yuzo

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[Yuzo Fujishima]

Hi, Thomas,

Thank you for the response.

Just as a data point, I'm using Xcode 3.1.4 on OS X 10.5.8 and I observed

by Activitiy Monitor better CPU usage (almost x16) with -parallelizeTargets .

Yuzo

[Thomas Van Lenten]

Actually, don't use this flag.

While parallel builds work in the IDE, it seems xcodebuild has issues with it.  Since enabling this on the bots, we've had some bad builds, where the app bundle didn't always regenerate.  In a clobber build it's easy to see, but on developers machines where you just do incremental builds, you run the risk of getting new and old code/resources, which could waste a lot of time debugging invalid builds.

TVL

[Eric Seidel]

I assume we've filed a Radar? http://radar.apple.com/

[Thomas Van Lenten]

On Fri, Jul 2, 2010 at 3:51 PM, Eric Seidel <ese...@chromium.org> wrote:

I assume we've filed a Radar?  http://radar.apple.com/

I've filed a few...  :)

TVL
 

[Yuzo Fujishima]

Thomas,

Thank you for the investigation and the important information.

Yuzo