[OE-core] [PATCH] python3: enable profile optimized builds

[Christopher Larson]

IMO PGO should really stay opt-in, not opt-out, given the performance
impact.

On Thu, Aug 23, 2018 at 1:28 AM Richard Purdie <
richard.purdie at linuxfoundation.org> wrote:

> On Wed, 2018-08-22 at 18:44 -0700, Andre McCurdy wrote:
> > On Thu, Aug 16, 2018 at 9:48 PM, Anuj Mittal <anuj.mittal at intel.com>
> > wrote:
> > > On 08/17/2018 03:31 AM, Andre McCurdy wrote:
> > > > On Wed, Aug 15, 2018 at 11:26 PM, Anuj Mittal <anuj.mittal at intel.
> > > > com> wrote:
> > > > Is it important to re-create the profile data during every build
> > > > or
> > > > would we get most of the same benefits from using reference data
> > > > which
> > > > is generated offline?
> > >
> > > We should get the same benefit using the data generated offline as
> > > long
> > > as the source code/configure options/flags are same I believe. I
> > > have
> > > only tried with data generate offline using the same build
> > > configuration
> > > though.
> >
> > As an additional data point, python do_compile now takes approx 18
> > minutes on my laptop. A single qemu-i386 thread loading one CPU core
> > at 100%, with nothing else being scheduled in parallel for most of
> > that time.
> >
> > If we can get most of the benefits of pgo with a pre-generated data
> > file then that might still be something to explore.
>
> I've also noticed the increased build times. I'd love to see if we
> could create an sstate object which would contain the pgo data and
> which didn't depend on the usual compiler/toolchain pieces, only the
> do_patch stage checksum. In theory, the same sstate object should be
> reusable between target/native/nativesdk too as long as we had the same
> python patchset (which I know we don't for native).
>
> Anyone fancy such a challenge? We should probably have a bug open for
> this at least...
>
> Cheers,
>
> Richard
>
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-- 
Christopher Larson
kergoth at gmail dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Senior Software Engineer, Mentor Graphics
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