* [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"
@ 2019-03-18 21:10 Matthias Kaehlcke
2019-03-18 21:47 ` Nick Desaulniers
2019-03-20 13:28 ` Masahiro Yamada
0 siblings, 2 replies; 6+ messages in thread
From: Matthias Kaehlcke @ 2019-03-18 21:10 UTC (permalink / raw)
To: Masahiro Yamada, Michal Marek
Cc: linux-kbuild, linux-kernel, Behan Webster, Peter Zijlstra,
H . Peter Anvin, Nick Desaulniers, Manoj Gupta, Tiancong Wang,
Stephen Hines, clang-built-linux, Matthias Kaehlcke
The clang option -Oz enables *aggressive* optimization for size,
which doesn't necessarily result in smaller images, but can have
negative impact on performance. Switch back to the less aggressive
-Os.
This reverts commit 6748cb3c299de1ffbe56733647b01dbcc398c419.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 9ef547fc7ffe..191f3ce3cb5e 100644
--- a/Makefile
+++ b/Makefile
@@ -667,7 +667,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
-KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
+KBUILD_CFLAGS += -Os
else
KBUILD_CFLAGS += -O2
endif
--
2.21.0.225.g810b269d1ac-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"
2019-03-18 21:10 [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang" Matthias Kaehlcke
@ 2019-03-18 21:47 ` Nick Desaulniers
2019-03-18 21:56 ` Matthias Kaehlcke
2019-03-20 13:28 ` Masahiro Yamada
1 sibling, 1 reply; 6+ messages in thread
From: Nick Desaulniers @ 2019-03-18 21:47 UTC (permalink / raw)
To: Matthias Kaehlcke
Cc: Masahiro Yamada, Michal Marek, Linux Kbuild mailing list, LKML,
Behan Webster, Peter Zijlstra, H . Peter Anvin, Manoj Gupta,
Tiancong Wang, Stephen Hines, clang-built-linux
On Mon, Mar 18, 2019 at 2:10 PM Matthias Kaehlcke <mka@chromium.org> wrote:
>
> The clang option -Oz enables *aggressive* optimization for size,
> which doesn't necessarily result in smaller images, but can have
> negative impact on performance. Switch back to the less aggressive
> -Os.
>
> This reverts commit 6748cb3c299de1ffbe56733647b01dbcc398c419.
Does scripts/checkpatch.pl complain about this format (full sha, no
title)? Not sure that necessitates a v2, but if so would be good to
mention that Clang generates excessive calls into libgcc/compiler-rt
at -Oz. Thanks for the patch and the discussion/sanity check.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> ---
> Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 9ef547fc7ffe..191f3ce3cb5e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -667,7 +667,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
> KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
>
> ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> -KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
> +KBUILD_CFLAGS += -Os
> else
> KBUILD_CFLAGS += -O2
> endif
> --
> 2.21.0.225.g810b269d1ac-goog
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"
2019-03-18 21:47 ` Nick Desaulniers
@ 2019-03-18 21:56 ` Matthias Kaehlcke
2019-03-18 22:07 ` hpa
0 siblings, 1 reply; 6+ messages in thread
From: Matthias Kaehlcke @ 2019-03-18 21:56 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Masahiro Yamada, Michal Marek, Linux Kbuild mailing list, LKML,
Behan Webster, Peter Zijlstra, H . Peter Anvin, Manoj Gupta,
Tiancong Wang, Stephen Hines, clang-built-linux
On Mon, Mar 18, 2019 at 02:47:13PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> On Mon, Mar 18, 2019 at 2:10 PM Matthias Kaehlcke <mka@chromium.org> wrote:
> >
> > The clang option -Oz enables *aggressive* optimization for size,
> > which doesn't necessarily result in smaller images, but can have
> > negative impact on performance. Switch back to the less aggressive
> > -Os.
> >
> > This reverts commit 6748cb3c299de1ffbe56733647b01dbcc398c419.
>
> Does scripts/checkpatch.pl complain about this format (full sha, no
> title)?
Nope, for reverts checkpatch is happy with it, I suppose because by
default the subject of the reverted patch is part of the revert's
subject.
> Not sure that necessitates a v2, but if so would be good to
> mention that Clang generates excessive calls into libgcc/compiler-rt
> at -Oz. Thanks for the patch and the discussion/sanity check.
I can send a v2 if 'needed'.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Thanks!
Matthias
> >
> > Suggested-by: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> > ---
> > Makefile | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 9ef547fc7ffe..191f3ce3cb5e 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -667,7 +667,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
> > KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
> >
> > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> > -KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
> > +KBUILD_CFLAGS += -Os
> > else
> > KBUILD_CFLAGS += -O2
> > endif
>
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"
2019-03-18 21:56 ` Matthias Kaehlcke
@ 2019-03-18 22:07 ` hpa
2019-03-18 22:23 ` Nick Desaulniers
0 siblings, 1 reply; 6+ messages in thread
From: hpa @ 2019-03-18 22:07 UTC (permalink / raw)
To: Matthias Kaehlcke, Nick Desaulniers
Cc: Masahiro Yamada, Michal Marek, Linux Kbuild mailing list, LKML,
Behan Webster, Peter Zijlstra, Manoj Gupta, Tiancong Wang,
Stephen Hines, clang-built-linux
On March 18, 2019 2:56:05 PM PDT, Matthias Kaehlcke <mka@chromium.org> wrote:
>On Mon, Mar 18, 2019 at 02:47:13PM -0700, 'Nick Desaulniers' via Clang
>Built Linux wrote:
>> On Mon, Mar 18, 2019 at 2:10 PM Matthias Kaehlcke <mka@chromium.org>
>wrote:
>> >
>> > The clang option -Oz enables *aggressive* optimization for size,
>> > which doesn't necessarily result in smaller images, but can have
>> > negative impact on performance. Switch back to the less aggressive
>> > -Os.
>> >
>> > This reverts commit 6748cb3c299de1ffbe56733647b01dbcc398c419.
>>
>> Does scripts/checkpatch.pl complain about this format (full sha, no
>> title)?
>
>Nope, for reverts checkpatch is happy with it, I suppose because by
>default the subject of the reverted patch is part of the revert's
>subject.
>
>> Not sure that necessitates a v2, but if so would be good to
>> mention that Clang generates excessive calls into libgcc/compiler-rt
>> at -Oz. Thanks for the patch and the discussion/sanity check.
>
>I can send a v2 if 'needed'.
>
>> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
>Thanks!
>
>Matthias
>
>> >
>> > Suggested-by: Peter Zijlstra <peterz@infradead.org>
>> > Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
>> > ---
>> > Makefile | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/Makefile b/Makefile
>> > index 9ef547fc7ffe..191f3ce3cb5e 100644
>> > --- a/Makefile
>> > +++ b/Makefile
>> > @@ -667,7 +667,7 @@ KBUILD_CFLAGS += $(call
>cc-disable-warning, format-overflow)
>> > KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
>> >
>> > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
>> > -KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
>> > +KBUILD_CFLAGS += -Os
>> > else
>> > KBUILD_CFLAGS += -O2
>> > endif
>>
>>
>>
Would be nice, still, to have -Ok.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"
2019-03-18 22:07 ` hpa
@ 2019-03-18 22:23 ` Nick Desaulniers
0 siblings, 0 replies; 6+ messages in thread
From: Nick Desaulniers @ 2019-03-18 22:23 UTC (permalink / raw)
To: H. Peter Anvin
Cc: Matthias Kaehlcke, Masahiro Yamada, Michal Marek,
Linux Kbuild mailing list, LKML, Behan Webster, Peter Zijlstra,
Manoj Gupta, Tiancong Wang, Stephen Hines, clang-built-linux
On Mon, Mar 18, 2019 at 3:07 PM <hpa@zytor.com> wrote:
>
> On March 18, 2019 2:56:05 PM PDT, Matthias Kaehlcke <mka@chromium.org> wrote:
> >> > KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
> >> >
> >> > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> >> > -KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
> >> > +KBUILD_CFLAGS += -Os
> >> > else
> >> > KBUILD_CFLAGS += -O2
> >> > endif
>
> Would be nice, still, to have -Ok.
April fools *is* coming up. 0:-)
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"
2019-03-18 21:10 [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang" Matthias Kaehlcke
2019-03-18 21:47 ` Nick Desaulniers
@ 2019-03-20 13:28 ` Masahiro Yamada
1 sibling, 0 replies; 6+ messages in thread
From: Masahiro Yamada @ 2019-03-20 13:28 UTC (permalink / raw)
To: Matthias Kaehlcke
Cc: Michal Marek, Linux Kbuild mailing list,
Linux Kernel Mailing List, Behan Webster, Peter Zijlstra,
H . Peter Anvin, Nick Desaulniers, Manoj Gupta, Tiancong Wang,
Stephen Hines, clang-built-linux
On Tue, Mar 19, 2019 at 6:10 AM Matthias Kaehlcke <mka@chromium.org> wrote:
>
> The clang option -Oz enables *aggressive* optimization for size,
> which doesn't necessarily result in smaller images, but can have
> negative impact on performance. Switch back to the less aggressive
> -Os.
>
> This reverts commit 6748cb3c299de1ffbe56733647b01dbcc398c419.
>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Applied to linux-kbuild/fixes. Thanks.
> ---
> Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 9ef547fc7ffe..191f3ce3cb5e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -667,7 +667,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
> KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
>
> ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> -KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
> +KBUILD_CFLAGS += -Os
> else
> KBUILD_CFLAGS += -O2
> endif
> --
> 2.21.0.225.g810b269d1ac-goog
--
Best Regards
Masahiro Yamada
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-03-20 13:29 UTC | newest]
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2019-03-18 21:10 [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang" Matthias Kaehlcke
2019-03-18 21:47 ` Nick Desaulniers
2019-03-18 21:56 ` Matthias Kaehlcke
2019-03-18 22:07 ` hpa
2019-03-18 22:23 ` Nick Desaulniers
2019-03-20 13:28 ` Masahiro Yamada
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