From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Arnd Bergmann <arnd@arndb.de>,
Segher Boessenkool <segher@kernel.crashing.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Thomas Gleixner <tglx@linutronix.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andy Lutomirski <luto@kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
"open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>
Subject: Re: Surprising code generated for vdso_read_begin()
Date: Wed, 19 Feb 2020 09:45:45 +0100 [thread overview]
Message-ID: <305fcee5-2e1b-ea4d-9a2a-a0e8034d40a8@c-s.fr> (raw)
In-Reply-To: <CAK8P3a11wX1zJ+TAacDTkYsrzvfdVmNrcB6OC23aFvCxF57opQ@mail.gmail.com>
Le 16/02/2020 à 19:10, Arnd Bergmann a écrit :
> On Sat, Jan 11, 2020 at 12:33 PM Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
>>
>> On Fri, Jan 10, 2020 at 07:45:44AM +0100, Christophe Leroy wrote:
>>> Le 09/01/2020 à 21:07, Segher Boessenkool a écrit :
>>>> It looks like the compiler did loop peeling. What GCC version is this?
>>>> Please try current trunk (to become GCC 10), or at least GCC 9?
>>>
>>> It is with GCC 5.5
>>>
>>> https://mirrors.edge.kernel.org/pub/tools/crosstool/ doesn't have more
>>> recent than 8.1
>>
>> Arnd, can you update the tools? We are at 8.3 and 9.2 now :-) Or is
>> this hard and/or painful to do?
>
> To follow up on this older thread, I have now uploaded 6.5, 7.5, 8.3 and 9.2
> binaries, as well as a recent 10.0 snapshot.
>
Thanks Arnd,
I have built the VDSO with 9.2, I get less performant result than with
8.2 (same performance as with 5.5).
After a quick look, I see:
- Irrelevant NOPs to align loops and stuff, allthough -mpcu=860 should
avoid that.
- A stack frame is set for saving r31 in __c_kernel_clock_gettime. GCC
8.1 don't need that, all VDSO functions are frameless with 8.1
Christophe
next prev parent reply other threads:[~2020-02-19 8:45 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-23 14:31 [RFC PATCH v2 00/10] powerpc/32: switch VDSO to C implementation Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 01/10] lib: vdso: ensure all arches have 32bit fallback Christophe Leroy
2019-12-24 2:07 ` Andy Lutomirski
2020-01-10 20:56 ` Thomas Gleixner
2020-01-10 21:02 ` Andy Lutomirski
2019-12-30 12:27 ` Arnd Bergmann
2020-01-02 11:29 ` Arnd Bergmann
2020-01-09 15:43 ` Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 02/10] lib: vdso: move call to fallback out of common code Christophe Leroy
2019-12-24 2:24 ` Andy Lutomirski
2019-12-24 11:41 ` christophe leroy
2019-12-24 12:09 ` Andy Lutomirski
2019-12-23 14:31 ` [RFC PATCH v2 03/10] lib: vdso: Change __cvdso_clock_gettime/getres_common() to __cvdso_clock_gettime/getres() Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 04/10] lib: vdso: get pointer to vdso data from the arch Christophe Leroy
2019-12-24 2:27 ` Andy Lutomirski
2019-12-24 11:53 ` christophe leroy
2019-12-24 12:15 ` Andy Lutomirski
2019-12-24 12:41 ` Andy Lutomirski
2019-12-24 14:46 ` Segher Boessenkool
2019-12-23 14:31 ` [RFC PATCH v2 05/10] lib: vdso: inline do_hres() Christophe Leroy
2019-12-24 2:29 ` Andy Lutomirski
2019-12-30 12:07 ` Arnd Bergmann
2020-01-10 21:07 ` Thomas Gleixner
2020-01-11 9:06 ` Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 06/10] lib: vdso: make do_coarse() return 0 Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 07/10] lib: vdso: don't use READ_ONCE() in __c_kernel_time() Christophe Leroy
2019-12-24 1:58 ` Andy Lutomirski
2019-12-24 11:12 ` christophe leroy
2019-12-24 12:04 ` Andy Lutomirski
2020-01-10 21:12 ` Thomas Gleixner
2020-01-11 8:05 ` Christophe Leroy
2020-01-11 11:07 ` Thomas Gleixner
2020-01-13 6:52 ` Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 08/10] lib: vdso: Avoid duplication in __cvdso_clock_getres() Christophe Leroy
2019-12-24 1:59 ` Andy Lutomirski
2019-12-23 14:31 ` [RFC PATCH v2 09/10] powerpc/vdso32: inline __get_datapage() Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 10/10] powerpc/32: Switch VDSO to C implementation Christophe Leroy
2020-01-09 17:52 ` Surprising code generated for vdso_read_begin() Christophe Leroy
2020-01-09 20:07 ` Segher Boessenkool
2020-01-10 6:45 ` Christophe Leroy
2020-01-11 11:33 ` Segher Boessenkool
2020-02-16 18:10 ` Arnd Bergmann
2020-02-19 8:45 ` Christophe Leroy [this message]
2020-02-19 9:52 ` Arnd Bergmann
2020-02-19 13:08 ` Segher Boessenkool
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