On Wed, Apr 24, 2019 at 1:46 AM Sasha Levin <sashal@xxxxxxxxxx> wrote: > > 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. > Dropped my private for-5.0/kbuild-cc-optimization Git branch. One less patch to carry with me... Thanks. - Sedat -
