On Tue, Apr 23, 2019 at 01:03:55PM -0700, Nathan Chancellor wrote:
On Tue, Apr 23, 2019 at 12:56:28PM -0700, Matthias Kaehlcke wrote:
On Tue, Apr 23, 2019 at 12:45:12PM -0700, Nathan Chancellor wrote:
> On Tue, Apr 23, 2019 at 03:35:12PM -0400, Sasha Levin wrote:
> > On Tue, Apr 23, 2019 at 12:04:21PM -0700, Nathan Chancellor wrote:
> > > Hi Greg and Sasha,
> > >
> > > Please apply this commit to 4.4 through 5.0 (patches are threaded in
> > > reply to this one), which will prevent Clang from emitting references
> > > to compiler runtime functions and doing some performance-killing
> > > optimization when using CONFIG_CC_OPTIMIZE_FOR_SIZE.
> > >
> > > Please let me know if I did something wrong or if there are any
> > > objections.
> >
> > This looks like a fix for a performance regression, which don't usually
> > end up in stable unless they are severe enough.
> >
>
> Yes and no. The original reason for the revert was because of the
> compiler runtime functions:
>
> https://lore.kernel.org/lkml/CAG5bF+S6OvBnsaR6UpMCqjDR9_hMo6qRMHGiW+iCaRYQW4C3YA@xxxxxxxxxxxxxx/
>
> The Chromium guys hit this [1] and have applied the patch for their
> kernels, I think it should be applied for everyone.
We picked it into our kernels because we needed a fix *now* to unbreak
our builds, but I agree it should be fixed at least in relevant LTS
versions.
Of course, I wasn't implying that was a bad thing :) it's further
justification for this being a stable worthy patch as it fixes a real
world issue and could fix more.
Okay, this makes more sense. The upstream commit message failed to
mention this.
I've queued it up.
--
Thanks,
Sasha
