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

[Derek Straka]

+1 for this being opt in.  It's a substantial hit to build time

On Thu, Aug 23, 2018 at 12:21 PM Christopher Larson <kergoth at gmail.com>
wrote:

> 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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