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

[Darren Hart]

On 11/15/2011 03:08 PM, Rifenbark, Scott M wrote:
> I haven't heard more on this.  Should I adjust the documents to
> suggest 2x for both these variables?

I think that's a reasonable thing to do, yes.

--
Darren

> 
> Scott
> 
> -----Original Message----- From: yocto-bounces at yoctoproject.org
> [mailto:yocto-bounces at yoctoproject.org] On Behalf Of Robert P. J.
> Day Sent: Thursday, November 03, 2011 10:42 AM To: Darren Hart Cc:
> yocto at yoctoproject.org Subject: Re: [yocto] what's the proper value
> for BB_NUMBER_THREADS?
> 
> On Thu, 3 Nov 2011, Darren Hart wrote:
> 
>> 
>> 
>> On 10/31/2011 10:39 AM, Gary Thomas wrote:
>>> 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.
>> 
>> 2x on each works well up to about 12 in my experience. Richard has
>> found benefits using 24 on a similar system with more memory.
>> However, if you aren't building on a monster machine, then 2x
>> serves as a reasonable rule of thumb.
> 
> since i vaguely recall that i was the one who asked about this, i can
> submit a patch for this unless someone else already wants to.  i can
> see that the places to change would be in some of the docs, as well
> as the comment in local.conf.sample.
> 
> anyone else want to take care of that?  anyone?  bueller?
> 
> rday
> 

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel