linux-kernel - Re: [PATCH v3 2/2] tile: add clock

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Message-ID: <CALAqxLWS4EBfLcjja4i3Bqt9PF-FpRJi5Em3YmhPupwd6BNr2g@mail.gmail.com>
Date:	Thu, 2 Oct 2014 10:41:49 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Chris Metcalf <cmetcalf@...era.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Henrik Austad <henrik@...tad.us>
Subject: Re: [PATCH v3 2/2] tile: add clock_gettime support to vDSO

On Thu, Oct 2, 2014 at 7:32 AM, Chris Metcalf <cmetcalf@...era.com> wrote:
> This change adds support for clock_gettime with CLOCK_REALTIME
> and CLOCK_MONOTONIC using vDSO.  It also updates the vdso
> struct nomenclature used for the clocks to match the x86 code
> to keep it easier to update going forward.
>
> We also support the *_COARSE clockid_t, for apps that want speed
> but aren't concerned about fine-grained timestamps; this saves
> about 20 cycles per call (see http://lwn.net/Articles/342018/).
>
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
> ---
>  arch/tile/include/asm/vdso.h          |  15 ++--
>  arch/tile/kernel/time.c               |  45 ++++++++---
>  arch/tile/kernel/vdso/vdso.lds.S      |   2 +
>  arch/tile/kernel/vdso/vgettimeofday.c | 145 +++++++++++++++++++++++++++++-----
>  4 files changed, 172 insertions(+), 35 deletions(-)
>
> v2: use the x86 code as a model to address both John Stultz's
>     observation about sub-nanosecond updates, as well as to address
>     Thomas Gleixner's observation about minimizing time spent with
>     the seqlock held.  Note that I kept the "unlikely" that Thomas
>     doubted would help, just for parallelism with the x86 code.
> v3: rebase onto 3.17-rc7


Looks ok to me.

Acked-by: John Stultz <john.stultz@...aro.org>

thanks
-john
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