From: Thomas Gleixner <tglx@linutronix.de>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
linux-arch <linux-arch@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mips@vger.kernel.org,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Russell King <linux@armlinux.org.uk>,
Ralf Baechle <ralf@linux-mips.org>,
Paul Burton <paul.burton@mips.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Mark Salyzyn <salyzyn@android.com>,
Peter Collingbourne <pcc@google.com>,
Shuah Khan <shuah@kernel.org>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Huw Davies <huw@codeweavers.com>
Subject: Re: [PATCH v6 00/19] Unify vDSOs across more architectures
Date: Fri, 14 Jun 2019 14:16:00 +0200 (CEST)
Message-ID: <alpine.DEB.2.21.1906141413070.1722@nanos.tec.linutronix.de> (raw)
In-Reply-To: <d96667d5-e43b-d33a-fbd0-5acfb4904316@arm.com>
On Tue, 4 Jun 2019, Vincenzo Frascino wrote:
> On 31/05/2019 09:46, Arnd Bergmann wrote:
> > One open question I touched in my review is whether we want to
> > have a vdso version of clock_getres() in all architectures or not.
> > I'd prefer to leave it out because there is very little advantage to
> > it over the system call (the results don't change at runtime and
> > can easily be cached by libc if performance ever matters), and
> > it takes up a small amount of memory for the implementation.
> >
>
> I thought about it and I ended up with what proposed in this patchset mainly for
> symmetry across all the architectures since in the end they use the same common
> code.
>
> It seems also that there is some performance impact (i.e.):
>
> clock-getres-monotonic: libc(system call): 296 nsec/call
> clock-getres-monotonic: libc(vdso): 5 nsec/call
clock_getres() is usually not a hot path operation.
> I agree with you though when you say that caching it in the libc is a
> possibility to overcome the performance impact.
>
> > We shouldn't just need it for consistency because all callers
> > would require implementing a fallback to the system call
> > anyway, to deal with old kernels.
libc has the fallback already. Let's aim for 1:1 replacement of the
architecture code first and then add the extra bits in separate patches.
Thanks,
tglx
next prev parent reply index
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-30 14:15 Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 01/19] kernel: Standardize vdso_datapage Vincenzo Frascino
2019-05-31 8:16 ` Arnd Bergmann
2019-06-04 12:05 ` Vincenzo Frascino
2019-06-10 17:47 ` Huw Davies
2019-06-10 9:27 ` Huw Davies
2019-06-10 10:17 ` Vincenzo Frascino
2019-06-10 10:31 ` Huw Davies
2019-06-10 11:07 ` Vincenzo Frascino
2019-06-10 11:37 ` Huw Davies
2019-05-30 14:15 ` [PATCH v6 02/19] kernel: Define gettimeofday vdso common code Vincenzo Frascino
2019-05-31 8:19 ` Arnd Bergmann
2019-06-04 12:08 ` Vincenzo Frascino
2019-06-10 9:31 ` Huw Davies
2019-06-10 10:18 ` Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 03/19] kernel: Unify update_vsyscall implementation Vincenzo Frascino
2019-06-10 9:34 ` Huw Davies
2019-06-10 10:19 ` Vincenzo Frascino
2019-06-14 11:10 ` Thomas Gleixner
2019-06-14 12:15 ` Vincenzo Frascino
2019-06-14 12:19 ` Thomas Gleixner
2019-06-14 12:25 ` Vincenzo Frascino
2019-06-14 13:07 ` Thomas Gleixner
2019-05-30 14:15 ` [PATCH v6 04/19] arm64: Substitute gettimeofday with C implementation Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 05/19] arm64: Build vDSO with -ffixed-x18 Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 06/19] arm64: compat: Add missing syscall numbers Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 07/19] arm64: compat: Expose signal related structures Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 08/19] arm64: compat: Generate asm offsets for signals Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 09/19] lib: vdso: Add compat support Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 10/19] arm64: compat: Add vDSO Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 11/19] arm64: Refactor vDSO code Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 12/19] arm64: compat: vDSO setup for compat layer Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 13/19] arm64: elf: vDSO code page discovery Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 14/19] arm64: compat: Get sigreturn trampolines from vDSO Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 15/19] arm64: Add vDSO compat support Vincenzo Frascino
2019-06-01 9:38 ` Catalin Marinas
2019-06-04 12:10 ` Vincenzo Frascino
2019-05-30 14:15 ` [PATCH v6 16/19] arm: Add support for generic vDSO Vincenzo Frascino
2019-05-31 8:32 ` Arnd Bergmann
2019-05-30 14:15 ` [PATCH v6 17/19] mips: " Vincenzo Frascino
2019-05-31 8:34 ` Arnd Bergmann
2019-06-03 14:54 ` Mark Salyzyn
2019-06-03 17:07 ` Arnd Bergmann
2019-05-30 14:15 ` [PATCH v6 18/19] x86: " Vincenzo Frascino
2019-05-30 15:41 ` Michael Kelley
2019-06-04 12:13 ` Vincenzo Frascino
2019-06-14 11:15 ` Thomas Gleixner
2019-06-14 21:17 ` Sasha Levin
2019-06-22 14:46 ` Thomas Gleixner
2019-06-23 19:09 ` Sasha Levin
2019-06-23 21:58 ` Stephen Rothwell
2019-06-24 0:24 ` Sasha Levin
2019-06-24 1:20 ` Stephen Rothwell
2019-06-23 22:12 ` Thomas Gleixner
2019-06-24 0:04 ` Michael Kelley
2019-06-24 0:25 ` Thomas Gleixner
2019-06-28 18:40 ` Michael Kelley
2019-05-30 14:15 ` [PATCH v6 19/19] kselftest: Extend vDSO selftest Vincenzo Frascino
2019-05-31 8:53 ` Arnd Bergmann
2019-05-31 8:46 ` [PATCH v6 00/19] Unify vDSOs across more architectures Arnd Bergmann
2019-06-04 12:04 ` Vincenzo Frascino
2019-06-04 12:12 ` Arnd Bergmann
2019-06-05 14:32 ` Vincenzo Frascino
2019-06-14 12:16 ` Thomas Gleixner [this message]
2019-06-14 12:19 ` Vincenzo Frascino
2019-06-20 6:17 ` Shijith Thotton
2019-06-20 8:55 ` Vincenzo Frascino
2019-06-20 16:27 ` Andre Przywara
2019-06-21 9:11 ` Vincenzo Frascino
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