From: Ingo Molnar <mingo@elte.hu>
To: Andy Lutomirski <luto@mit.edu>
Cc: x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFT/PATCH v2 6/6] x86-64: Turn off -pg and turn on -foptimize-sibling-calls for vDSO
Date: Thu, 7 Apr 2011 10:03:01 +0200 [thread overview]
Message-ID: <20110407080301.GE24879@elte.hu> (raw)
In-Reply-To: <78b66387ae46799690413ea241053e4d592cf728.1302137785.git.luto@mit.edu>
* Andy Lutomirski <luto@mit.edu> wrote:
> The vDSO isn't part of the kernel, so profiling and kernel
> backtraces don't really matter.
>
> Signed-off-by: Andy Lutomirski <luto@mit.edu>
> ---
> arch/x86/vdso/Makefile | 15 ++++++++++++++-
> 1 files changed, 14 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
> index a651861..bef0bc9 100644
> --- a/arch/x86/vdso/Makefile
> +++ b/arch/x86/vdso/Makefile
> @@ -37,11 +37,24 @@ $(obj)/%.so: OBJCOPYFLAGS := -S
> $(obj)/%.so: $(obj)/%.so.dbg FORCE
> $(call if_changed,objcopy)
>
> +#
> +# Don't omit frame pointers for ease of userspace debugging, but do
> +# optimize sibling calls.
> +#
> CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
> - $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector)
> + $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
> + -fno-omit-frame-pointer -foptimize-sibling-calls
>
> $(vobjs): KBUILD_CFLAGS += $(CFL)
>
> +#
> +# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
> +#
> +CFLAGS_REMOVE_vdso-note.o = -pg
> +CFLAGS_REMOVE_vclock_gettime.o = -pg
> +CFLAGS_REMOVE_vgetcpu.o = -pg
> +CFLAGS_REMOVE_vvar.o = -pg
The comment makes no sense in this form, -pg is not used for profiling but
in-kernel tracing.
Also, please do not do multiple changes in a single patch, split out the -pg,
the -fomit-frame-pointers and the -foptimize-sibling-calls change into two
patches. This will also help bisection, should some GCC version do something
silly with -foptimize-sibling-calls ...
Thanks,
Ingo
prev parent reply other threads:[~2011-04-07 8:03 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-07 2:03 [RFT/PATCH v2 0/6] Micro-optimize vclock_gettime Andy Lutomirski
2011-04-07 2:03 ` [RFT/PATCH v2 1/6] x86-64: Clean up vdso/kernel shared variables Andy Lutomirski
2011-04-07 8:08 ` Ingo Molnar
2011-04-07 2:03 ` [RFT/PATCH v2 2/6] x86-64: Optimize vread_tsc's barriers Andy Lutomirski
2011-04-07 8:25 ` Ingo Molnar
2011-04-07 11:44 ` Andrew Lutomirski
2011-04-07 15:23 ` Andi Kleen
2011-04-07 17:28 ` Ingo Molnar
2011-04-07 16:18 ` Linus Torvalds
2011-04-07 16:42 ` Andi Kleen
2011-04-07 17:20 ` Linus Torvalds
2011-04-07 18:15 ` Andi Kleen
2011-04-07 18:30 ` Linus Torvalds
2011-04-07 21:26 ` Andrew Lutomirski
2011-04-08 17:59 ` Andrew Lutomirski
2011-04-09 11:51 ` Ingo Molnar
2011-04-07 21:43 ` Raghavendra D Prabhu
2011-04-07 22:52 ` Andi Kleen
2011-04-07 2:04 ` [RFT/PATCH v2 3/6] x86-64: Don't generate cmov in vread_tsc Andy Lutomirski
2011-04-07 7:54 ` Ingo Molnar
2011-04-07 11:25 ` Andrew Lutomirski
2011-04-07 2:04 ` [RFT/PATCH v2 4/6] x86-64: vclock_gettime(CLOCK_MONOTONIC) can't ever see nsec < 0 Andy Lutomirski
2011-04-07 7:57 ` Ingo Molnar
2011-04-07 11:27 ` Andrew Lutomirski
2011-04-07 2:04 ` [RFT/PATCH v2 5/6] x86-64: Move vread_tsc into a new file with sensible options Andy Lutomirski
2011-04-07 2:04 ` [RFT/PATCH v2 6/6] x86-64: Turn off -pg and turn on -foptimize-sibling-calls for vDSO Andy Lutomirski
2011-04-07 8:03 ` Ingo Molnar [this message]
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