[poky] [RFC PATCH 1/1] local.conf.sample: update suggestions for BB_NUMBER_THREADS and PARALLEL_MAKE

[Tom Rini]

On 06/17/2011 08:21 PM, Darren Hart wrote:
> 
> 
> On 06/17/2011 08:16 PM, Joshua Lock wrote:
>> It's been suggested that BB_NUMBER_THREADS should be 2 * the number of cores
>> and PARALLEL_MAKE should be equal to the number of cores available on the
>> build machine.
>>
>> Update local.conf.sample to suggest this.
>>
>> Signed-off-by: Joshua Lock <josh at linux.intel.com>
>> ---
>>  meta-yocto/conf/local.conf.sample |    4 +++-
>>  1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/meta-yocto/conf/local.conf.sample b/meta-yocto/conf/local.conf.sample
>> index ea32b81..43d06e6 100644
>> --- a/meta-yocto/conf/local.conf.sample
>> +++ b/meta-yocto/conf/local.conf.sample
>> @@ -9,7 +9,9 @@ CONF_VERSION = "1"
>>  #SSTATE_DIR ?= "${TOPDIR}/sstate-cache"
>>  
>>  # Uncomment and set to allow bitbake to execute multiple tasks at once.
>> -# For a quadcore, BB_NUMBER_THREADS = "4", PARALLEL_MAKE = "-j 4" would
>> +# Recommended values are twice the number of processor cores for
>> +# BB_NUMBER_THREADS and the number of processor cores for PARALLEL_MAKE
>> +# For a quadcore, BB_NUMBER_THREADS = "8", PARALLEL_MAKE = "-j 4" would
> 
> Hrm, where is this coming from? In my experience it works better the
> other way around. We probably also need to be explicit about cores
> versus threads.

On my older quad-core AMD box, -j 6 / 4 threads is where it's at, and
our testing / poking around on other hardware bears that out (for
example my Dell M4400 laptop is -j 3 / 2 threads).  That said, for much
more beefy configurations, we use -j 16, and 12 threads (on an 8 core
machine with 12GB mem).  I think perhaps the best change here is to keep
it at 1:1 in the sample (since we've also run into older hardware too)
and explain that anywhere between 1:1 and 2*core:2*core could work best
depending on setup, ymmv, etc.

-- 
Tom Rini
Mentor Graphics Corporation