[OE-core] [PATCH] local.conf.sample: Have comments ready to go for quad-core (4 -> 8).

[Elvis Dowson]

On Apr 18, 2013, at 8:51 PM, "Robert P. J. Day" <rpjday at crashcourse.ca> wrote:

> On Thu, 18 Apr 2013, Enrico Scholz wrote:
> 
>> "Robert P. J. Day" <rpjday-L09J2beyid0N/H6P543EQg at public.gmane.org>
>> writes:
>> 
>>> Have default, commented values for parallelism reflect quad-core
>>> hosts.
>> 
>> fwiw, I use
>> 
>> PARALLEL_MAKE = "\
>>  -j ${@int(os.sysconf(os.sysconf_names['SC_NPROCESSORS_ONLN'])) * 2} \
>>  -l ${@int(os.sysconf(os.sysconf_names['SC_NPROCESSORS_ONLN'])) * 150/100} \
>> "
>> 
>> BB_NUMBER_THREADS ?= "\
>>  ${@int(os.sysconf(os.sysconf_names['SC_NPROCESSORS_ONLN'])) * 150/100}"
>> 
>> 
>> which adjusts parallelism automatically.
> 
>  i'd be perfectly fine with that, too, if someone wants to put that
> in instead.

I've noticed that on a quad-core machine (i7) the best setting is to leave it at 6 for 
BB_NUMBER_THREADS and PARALLEL_MAKE.

8, 16, etc don't have any discernable impact, perhaps save 30 to 40 seconds off
a build. The 3.5Ghz standard CPU frequency can be over-clocked to as high
as 4.5GHz, but I tested it out at 4.2Ghz and 3.8Ghz, and the difference was
only 2 to 3 minutes between 3.8GHz and 4.2GHz over-clocked, so I currently
leave it at 3.8GHz over-clocked.

I'm using two SSDs in a RAID 0 striped configuration, and build times is 
around 22 minutes for a Zynq-7-ZC702 build for core-image-minimal.

Elvis Dowson