linux-kernel - Re: [PATCH v2 10/10] arm+arm64: vdso: Add support for CLOCK

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Message-ID: <20171030152517.GB1705@arm.com>
Date:   Mon, 30 Oct 2017 15:25:18 +0000
From:   Will Deacon <will.deacon@....com>
To:     Mark Salyzyn <salyzyn@...roid.com>
Cc:     linux-kernel@...r.kernel.org, james.morse@....com,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Salyzyn <salyzyn@...gle.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        John Stultz <john.stultz@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Laura Abbott <labbott@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 10/10] arm+arm64: vdso: Add support for CLOCK_BOOTTIME

Hi Mark,

On Thu, Oct 12, 2017 at 04:01:45PM -0700, Mark Salyzyn wrote:
> Add a case for CLOCK_BOOTTIME as it is popular for measuring
> relative time on systems expected to suspend() or hibernate().
> 
> Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
> 
> v2: rebased and changed from 3/3 to 10/10, fortified commit message.
> ---
>  arch/arm/include/asm/vdso_datapage.h   |  1 +
>  arch/arm/kernel/vdso.c                 |  1 +
>  arch/arm/vdso/vgettimeofday.c          | 56 ++++++++++++++++++++++++++++++++++
>  arch/arm64/include/asm/vdso_datapage.h |  1 +
>  arch/arm64/kernel/vdso.c               |  1 +
>  5 files changed, 60 insertions(+)

Can you elaborate a bit on the use-case for CLOCK_BOOTTIME, please, so
that we can justify accelerating it in the vDSO?

Thanks,

Will