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

[Yi Qingliang]

On Thursday, April 18, 2013 09:57:16 PM Elvis Dowson wrote:
> 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.
maybe we need consider the hyper-threading.

	CPU_PROC_NUM="`grep "^processor" /proc/cpuinfo | sort -u | wc -l`"
	CPU_CORE_NUM="`grep "^core id" /proc/cpuinfo | sort -u | wc -l`"

> 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
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-- 
Nanjing Jilong
Yi Qingliang
niqingliang2003 at gmail.com