Re: [edk2-devel] [PATCH] OvmfPkg: enable multiprocessor builds when using build.sh

["Jordan Justen" <jordan.l.justen@intel.com>]

On 2019-07-23 00:44:06, Laszlo Ersek wrote:
> On 07/23/19 02:00, Rebecca Cran wrote:
> > On 2019-07-22 17:14, Jordan Justen wrote:
> >>
> >> I was suggesting that if they didn't specify -n as a param to
> >> build.sh, then build.sh should not send -n to the edk2 build command.
> >> The effect would be for the edk2 build command to check
> >> Conf/target.txt. By default, I think target.txt will not set
> >> THREADNUMBER, so "0" would still be the result.
> >>
> >> Yet, it would give them the option to set it in Conf/target.txt.
> >> Today, since we always use the -n param, target.txt is always ignored
> >> for this parameter.
> > 
> > 
> > On a related topic, I wonder if we should add a "-j" parameter if we
> > build BaseTools for users (e.g. "make -j4 -C BaseTools")? I've found
> > that it can be pretty slow without it: on my system adding -j4 reduces
> > build time from 55 seconds to 15. Going higher doesn't seem to produce
> > much more benefit: -j32 (on a ThreadRipper system) reduces it to 12 seconds.
> > 
> > 
> 
> Passing
> 
>   -j $(getconf _NPROCESSORS_ONLN)
> 
> to "make" (for building BaseTools) makes sense, IMO.

I guess the concern might be that we'll be running a bunch of
make invocations in parallel, each trying to spawn a compilation for
each thread. O(n^2) compilations. :)

In the make man-page for -j: "When make invokes a sub-make, all
instances of make will coordinate to run the specified number of jobs
at a time;", but I'm not sure if that's how `build -n` is implemented.
(With make...)

Since python writes the makefiles, it could be used instead of
getconf, right?

What we need is someone to make the ninja-build backend for BaseTools.
:)

-Jordan