Re: [OE-core] [PATCH v5 01/11] lto: Add global LTO distro policy file

Andreas Müller
2020-11-09T20:18:46Z

On Mon, Nov 9, 2020 at 8:15 PM Khem Raj <raj.khem@gmail.com> wrote:
>
> On Mon, Nov 9, 2020 at 12:30 AM Andreas Müller <schnitzeltony@gmail.com> wrote:
> >
> > On Mon, Nov 9, 2020 at 1:02 AM Khem Raj <raj.khem@gmail.com> wrote:
> > >
> > > Distros which want to enable LTO can utilize this file, it only covers
> > > packages from OE-Core, other layers should include there own exclusion
> > > list for recipe which dont work with LTO
> > >
> > > Document the needed changes in local.conf.extended
> > >
> > Maybe I missed something but I haven't seen a word why I should want
> > link time optimization. And from the patches I see here it seems we
> > are about to create another contributor's burden.
> >
>
> Thanks for your feedback. LTO is quite beneficial for the kind of
> images OE is targeting,
> It results in smaller binaries and better optimizations as well. LTO
> has been around for a while
> in GCC but it is becoming useful with gcc10+ and more distros e.g.
> Fedora/SuSE are also starting
> to use LTO distro wide which means we will be able to reuse the
> upstream work that's ongoing in
> different packages. You can see there are patches already floating to
> enable it for poky-tiny already
> so OE userbase is already starting to use it. Moreover, its already
> default for many packages themselves
> so you might already be using it at package level e.g. systemd
>
> This is similar to what we did for enabling security flags. As you
> can see, these changes are currently optional. This means they won't
> go into effect for
> distros without them choosing to use it via DISTRO_FEATURES. Since it
> takes a bit to get
> such changes stable, we might keep it disabled by default for the next
> release depending upon
> how it pans out. Eventually, the plan is to enable it for poky/yocto distro.
>
> As far as the contribution burden, I think it won't be a blocker until
> it becomes one of the tested configurations
> on yocto auto-builder.
>
> Feel free to express if you have more concerns.
>
Thanks for explanation. At least I understand better now why you (and
others?) are taking efforts on LTO support.

Andreas