[yocto] what's the proper value for BB_NUMBER_THREADS?

[Gary Thomas]

On 2011-10-31 11:25, Robert P. J. Day wrote:
> On Mon, 31 Oct 2011, Mark Hatle wrote:
>
>> On 10/30/11 11:15 AM, Robert P. J. Day wrote:
>>> On Sun, 30 Oct 2011, Christian Gagneraud wrote:
>>>
>>>> On 30/10/11 15:32, Robert P. J. Day wrote:
>>>>>
>>>>>     all the docs recommend twice the number of cores (AFAICT), yet the
>>>>> template local.conf file suggests that, for a quad core, the value of
>>>>> 4 would be appropriate.  shouldn't that say 8?  same with
>>>>> PARALLEL_MAKE?
>>>>
>>>> Hi Robert,
>>>>
>>>> The Poky ref manual says (rule of thumb) x2 for BB_NUMBER_THREADS,
>>>> and x1.5 for PARALLEL_MAKE.
>>>
>>>    if that's the case, anyone object to my submitting a patch to
>>> update local.conf.sample appropriately?
>>>
>>> rday
>>>
>>
>> I agree the manual and local.conf files should match.  The issue
>> seems to be that the perfect values are subjective.  Things like
>> memory, disk speed, chipset latency, and of course processor
>> speed/cores all affect the optimal setting. But we do need a
>> consistent rule of thumb..  I myself usually use x2 for both THREADS
>> and MAKE.
>
>    that's what i would normally use, assuming that having an overly
> high value for either of those settings can't possibly hurt.  if
> that's the consensus, i can adjust the references to say 2x everywhere
> that i know of.  just let me know.

Look back in the archives - I think it was Richard that did a fairly
extensive study of this and he (whoever it was) found that there were
saturation points and trying to get beyond them had a negative impact.

-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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