From: Andy Chiu <andy.chiu@sifive.com>
To: Guo Ren <guoren@kernel.org>
Cc: palmer@dabbelt.com, paul.walmsley@sifive.com,
aou@eecs.berkeley.edu, rostedt@goodmis.org, mingo@redhat.com,
peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com,
ardb@kernel.org, greentime.hu@sifive.com, zong.li@sifive.com,
kernel@esmil.dk, linux-riscv@lists.infradead.org,
Kito Cheng <kito.cheng@sifive.com>
Subject: Re: [PATCH RFC v2 riscv/for-next 1/5] riscv: align ftrace to 4 Byte boundary and increase ftrace prologue size
Date: Sat, 17 Sep 2022 02:15:48 +0100 [thread overview]
Message-ID: <CABgGipWD0_cxf6=gTpnc-1YvVMAF-ghyr1EZYULioo0GYZLtRQ@mail.gmail.com> (raw)
In-Reply-To: <CAJF2gTT8+TWFoP6pUPOHOLWFXg-5N0U3jDYvqAp_sO+qgqS5Ow@mail.gmail.com>
On Thu, Sep 15, 2022 at 2:54 PM Guo Ren <guoren@kernel.org> wrote:
>
> On Tue, Sep 13, 2022 at 5:44 PM Andy Chiu <andy.chiu@sifive.com> wrote:
> >
> > However, we found the -falign-functions alone was not strong enoungh to
> > make all functions align as required. In fact, cold functions are not
> > aligned after turning on optimizations. We consider this is a bug in GCC
> > and turn off guess-branch-probility as a workaround to align all
> > functions.
> Disable pgo static optimization would reduce the code performance. I
> think we need to fix that problem in GCC, and pgo is a default-enabled
> optimization.
I would like to see this fix in GCC as well. Or the other way is to
reserve extra bytes (like, 2 bytes) and pick an aligned address in
software.
> >
> > GCC bug id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345
> >
> > Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> > Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> > ---
> > arch/riscv/Makefile | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> > index 3fa8ef336822..fd8069f59a59 100644
> > --- a/arch/riscv/Makefile
> > +++ b/arch/riscv/Makefile
> > @@ -11,7 +11,7 @@ LDFLAGS_vmlinux :=
> > ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
> > LDFLAGS_vmlinux := --no-relax
> > KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
> > - CC_FLAGS_FTRACE := -fpatchable-function-entry=8
> > + CC_FLAGS_FTRACE := -fpatchable-function-entry=12 -falign-functions=4 -fno-guess-branch-probability
> Another fixup should be covered, eg:
>
> +ifeq ($(CONFIG_RISCV_ISA_C),y)
> + CC_FLAGS_FTRACE := -fpatchable-function-entry=12
> +else
> + CC_FLAGS_FTRACE := -fpatchable-function-entry=6
> +endif
>
Thanks for reminding. Yes, we have to do that.
Regards,
Andy
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next prev parent reply other threads:[~2022-09-17 1:16 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 9:42 [PATCH RFC v2 riscv/for-next 0/5] Enable ftrace with kernel preemption for RISC-V Andy Chiu
2022-09-13 9:42 ` [PATCH RFC v2 riscv/for-next 1/5] riscv: align ftrace to 4 Byte boundary and increase ftrace prologue size Andy Chiu
2022-09-15 13:53 ` Guo Ren
2022-09-17 1:15 ` Andy Chiu [this message]
2022-09-13 9:42 ` [PATCH RFC v2 riscv/for-next 2/5] riscv: export patch_insn_write Andy Chiu
2022-09-13 9:42 ` [PATCH RFC v2 riscv/for-next 3/5] riscv: ftrace: use indirect jump to work with kernel preemption Andy Chiu
2022-09-14 13:45 ` Guo Ren
2022-09-15 13:30 ` Guo Ren
2022-09-17 1:04 ` Andy Chiu
2022-09-17 10:56 ` Guo Ren
2024-02-20 14:17 ` Evgenii Shatokhin
2022-09-13 9:42 ` [PATCH RFC v2 riscv/for-next 4/5] riscv: ftrace: do not use stop_machine to update code Andy Chiu
2022-09-13 9:42 ` [PATCH RFC v2 riscv/for-next 5/5] riscv: align arch_static_branch function Andy Chiu
2022-09-14 14:06 ` Guo Ren
2022-09-16 23:54 ` Andy Chiu
2022-09-17 0:22 ` Guo Ren
2022-09-17 18:17 ` [PATCH] riscv: jump_label: Optimize size with RISCV_ISA_C guoren
2022-09-17 18:38 ` [PATCH RFC v2 riscv/for-next 5/5] riscv: align arch_static_branch function guoren
2022-09-17 23:49 ` Guo Ren
2022-09-17 23:59 ` Guo Ren
2022-09-18 0:12 ` Jessica Clarke
2022-09-18 0:46 ` Guo Ren
2022-09-14 14:24 ` Jessica Clarke
2022-09-15 1:47 ` Guo Ren
2022-09-15 2:34 ` Jessica Clarke
2024-02-13 19:42 ` [PATCH RFC v2 riscv/for-next 0/5] Enable ftrace with kernel preemption for RISC-V Evgenii Shatokhin
2024-02-21 5:27 ` Andy Chiu
2024-02-21 16:55 ` Evgenii Shatokhin
2024-03-06 20:57 ` Alexandre Ghiti
2024-03-07 8:35 ` Evgenii Shatokhin
2024-03-07 12:27 ` Andy Chiu
2024-03-07 13:21 ` Alexandre Ghiti
2024-03-07 15:57 ` Samuel Holland
2024-03-11 14:24 ` Andy Chiu
2024-03-19 14:50 ` Alexandre Ghiti
2024-03-19 14:58 ` Conor Dooley
2024-03-20 16:37 ` Andy Chiu
2024-03-18 15:31 ` Andy Chiu
2024-03-19 15:32 ` Evgenii Shatokhin
2024-03-20 16:38 ` Andy Chiu
2024-03-19 17:37 ` Alexandre Ghiti
2024-03-20 16:36 ` Andy Chiu
2024-03-21 11:02 ` Alexandre Ghiti
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