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Re: [RFC/PATCH] ARM: VDSO support
- From: Nathan Lynch <Nathan_Lynch at codesourcery dot com>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: <libc-alpha at sourceware dot org>
- Date: Mon, 6 Apr 2015 17:53:10 -0500
- Subject: Re: [RFC/PATCH] ARM: VDSO support
- Authentication-results: sourceware.org; auth=none
- References: <1428081934-22419-1-git-send-email-nathan_lynch at codesourcery dot com> <5522D8CA dot 3000001 at linaro dot org>
On 04/06/2015 02:04 PM, Adhemerval Zanella wrote:
> Hi,
>
> On 03-04-2015 14:25, Nathan Lynch wrote:
>> Future versions of Linux on 32-bit ARM are expected to provide fast
>> user-space implementations of the following system calls:
>>
>> - gettimeofday
>> - clock_gettime
>>
>> The kernel implementation depends on the ARMv7 Generic Timers
>> Extension to accelerate these system calls. So CPUs such as
>> Cortex-A15 and -A7 benefit, while Cortex-A9, -A8, and pre-v7 CPUs do
>> not.
>>
>> The kernel support is currently in linux-next and is slated for
>> inclusion in Linux 4.1. I plan to ping or resubmit this patch once
>> Linux 4.1 is released, but would appreciate any preliminary review in
>> the meantime. For reference, the current kernel patch submission may
>> be found here:
>>
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/332573.html
>>
>> This patch adds support for the ARM VDSO to glibc. I have run make
>> check on OMAP5 using kernels with and without the VDSO, with no new
>> failures.
>
> LGTM. Also, you can tune latency a bit more by using IFUNC on gettimeofday.
Thanks, I'll check into that.