Patchwork local.conf.sample: Suggest parallelism of twice the number of cores.

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Submitter Robert P. J. Day
Date Jan. 9, 2013, 6:14 p.m.
Message ID <alpine.DEB.2.02.1301091312270.14396@oneiric>
Download mbox | patch
Permalink /patch/42407/
State New
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Comments

Robert P. J. Day - Jan. 9, 2013, 6:14 p.m.
To be consistent with the Yocto Quick Start Guide, recommend that
parallelism represent twice the number of cores on a multi-core
machine.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

---
Saul Wold - Jan. 9, 2013, 6:31 p.m.
On 01/09/2013 10:14 AM, Robert P. J. Day wrote:
>
> To be consistent with the Yocto Quick Start Guide, recommend that
> parallelism represent twice the number of cores on a multi-core
> machine.
>
> Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
>
> ---
>
> diff --git a/meta/conf/local.conf.sample b/meta/conf/local.conf.sample
> index 859eb93..46187ce 100644
> --- a/meta/conf/local.conf.sample
> +++ b/meta/conf/local.conf.sample
> @@ -24,9 +24,9 @@
>   #
>   #PARALLEL_MAKE = "-j 4"
>   #
> -# For a quad-core machine, BB_NUMBER_THREADS = "4", PARALLEL_MAKE = "-j 4" would
> -# be appropriate for example.
> -
> +# If you have a multi-core machine, you would normally set both of these variables
> +# to twice the number of cores.  So for a quad-core machine, it would be appropriate
> +# to set BB_NUMBER_THREADS = "8" and PARALLEL_MAKE = "-j 8".

I think adding a note to ensure that hyperthreading is enabled would be 
appropriate, then number of threads = number of hyperthreaded cores (4 
vs 8).

Sau!

>   #
>   # Machine Selection
>   #
>
Enrico Scholz - Jan. 9, 2013, 6:43 p.m.
Saul Wold <sgw-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> writes:

>>   #PARALLEL_MAKE = "-j 4"
>>   #
>> -# For a quad-core machine, BB_NUMBER_THREADS = "4", PARALLEL_MAKE = "-j 4" would
>> -# be appropriate for example.
>> -
>> +# If you have a multi-core machine, you would normally set both of these variables
>> +# to twice the number of cores.  So for a quad-core machine, it would be appropriate
>> +# to set BB_NUMBER_THREADS = "8" and PARALLEL_MAKE = "-j 8".
>
> I think adding a note to ensure that hyperthreading is enabled would
> be appropriate, then number of threads = number of hyperthreaded cores
> (4 vs 8).

what about a general

| BB_NUMBER_THREADS ??= "${@os.sysconf(os.sysconf_names['SC_NPROCESSORS_ONLN'])}"

in bitbake.conf?  Or the sqrt() of it in in both PARALLEL_MAKE and
BB_NUMBER_THREADS...


Enrico

Patch

diff --git a/meta/conf/local.conf.sample b/meta/conf/local.conf.sample
index 859eb93..46187ce 100644
--- a/meta/conf/local.conf.sample
+++ b/meta/conf/local.conf.sample
@@ -24,9 +24,9 @@ 
 #
 #PARALLEL_MAKE = "-j 4"
 #
-# For a quad-core machine, BB_NUMBER_THREADS = "4", PARALLEL_MAKE = "-j 4" would
-# be appropriate for example.
-
+# If you have a multi-core machine, you would normally set both of these variables
+# to twice the number of cores.  So for a quad-core machine, it would be appropriate
+# to set BB_NUMBER_THREADS = "8" and PARALLEL_MAKE = "-j 8".
 #
 # Machine Selection
 #