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Date: Thu, 21 Nov 2013 09:04:40 +0100
From: Ulf Samuelsson <openembedded-core@emagii.com>
Organization: eMagii
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Subject: Re: Improving Build Speed
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>>       Why restrict PARALLEL_MAKE to anything less than the number of H/W
>> threads in the machine?
>>
>>       Came up with a construct PARALLEL_HIGH which is defined alongside
>> PARALLEL_MAKE in conf/local.conf
>>
>>       PARALLEL_MAKE = "-j8"
>>       PARALLEL_HIGH = "-j24"
>>
>>       In the appropriate recipes, which seems to be processed by bitbake
>> in solitude I do:
>>
>>       PARALLEL_HIGH ?= "${PARALLEL_MAKE}"
>>       PARALLEL_MAKE  = "${PARALLEL_HIGH}"
>>
>>       This means that they will try to use each H/W thread.
> Please benchmark the difference. I suspect we can just set the high
> number of make for everything. Note that few makefiles are well enough
> written to benefit from high levels of make (webkit being an notable
> exception).
>
It looks like it is shaving off  ~2 minutes from a build which normally 
takes ~84 minutes.

First build
PARALLEL_MAKE = "-j12"
PARALLEL_HIGH = "-j24"
BB_NUMBER_THREADS = "24"
real    83m24.093s

Second build
PARALLEL_MAKE = "-j12"
PARALLEL_HIGH = "-j12"
BB_NUMBER_THREADS = "24"
real    85m12.007s


BR
Ulf

> Cheers, Richard _______________________________________________ 
> Openembedded-core mailing list 
> Openembedded-core@lists.openembedded.org 
> http://lists.openembedded.org/mailman/listinfo/openembedded-core 


-- 
Best Regards
Ulf Samuelsson
eMagii