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From: Sedat Dilek <sedat.dilek@gmail.com>
To: Sasha Levin <sashal@kernel.org>
Cc: Nathan Chancellor <natechancellor@gmail.com>,
	Matthias Kaehlcke <mka@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org,
	Nick Desaulniers <ndesaulniers@google.com>,
	Clang-Built-Linux ML <clang-built-linux@googlegroups.com>
Subject: Re: Backport of commit a75bb4eb9e565b9f5115e2e8c07377ce32cbe69a
Date: Wed, 24 Apr 2019 07:58:05 +0200	[thread overview]
Message-ID: <CA+icZUWgf=Np0oBv-uBpXku_EZ0J1rk6XJVVvQdjnwEwZrBrxA@mail.gmail.com> (raw)
In-Reply-To: <20190423234608.GU17719@sasha-vm>

On Wed, Apr 24, 2019 at 1:46 AM Sasha Levin <sashal@kernel.org> 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@mail.gmail.com/
> >> >
> >> > 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 -

      reply	other threads:[~2019-04-24  5:58 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-23 19:04 Nathan Chancellor
2019-04-23 19:04 ` [PATCH 4.14] Revert "kbuild: use -Oz instead of -Os when using clang" Nathan Chancellor
2019-04-23 19:04 ` [PATCH 4.19] " Nathan Chancellor
2019-04-23 19:04 ` [PATCH 4.4] " Nathan Chancellor
2019-04-23 19:04 ` [PATCH 4.9] " Nathan Chancellor
2019-04-23 19:04 ` [PATCH 5.0] " Nathan Chancellor
2019-04-23 19:35 ` Backport of commit a75bb4eb9e565b9f5115e2e8c07377ce32cbe69a Sasha Levin
2019-04-23 19:42   ` Nick Desaulniers
2019-04-23 19:45   ` Nathan Chancellor
2019-04-23 19:56     ` Matthias Kaehlcke
2019-04-23 20:03       ` Nathan Chancellor
2019-04-23 23:46         ` Sasha Levin
2019-04-24  5:58           ` Sedat Dilek [this message]

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