[PATCH v6] powerpc/vdso64: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE

[Naveen N. Rao]

Hi Santosh,
This seems to have gone from v4 to v6 -- did I miss v5?

On 2017/10/10 11:10PM, Santosh Sivaraj wrote:
> Current vDSO64 implementation does not have support for coarse clocks
> (CLOCK_MONOTONIC_COARSE, CLOCK_REALTIME_COARSE), for which it falls back
> to system call, increasing the response time, vDSO implementation reduces
> the cycle time. Below is a benchmark of the difference in execution times.
> 
> (Non-coarse clocks are also included just for completion)
> 
> clock-gettime-realtime: syscall: 172 nsec/call
> clock-gettime-realtime:    libc: 28 nsec/call
> clock-gettime-realtime:    vdso: 22 nsec/call
> clock-gettime-monotonic: syscall: 171 nsec/call
> clock-gettime-monotonic:    libc: 30 nsec/call
> clock-gettime-monotonic:    vdso: 25 nsec/call
> clock-gettime-realtime-coarse: syscall: 153 nsec/call
> clock-gettime-realtime-coarse:    libc: 16 nsec/call
> clock-gettime-realtime-coarse:    vdso: 10 nsec/call
> clock-gettime-monotonic-coarse: syscall: 167 nsec/call
> clock-gettime-monotonic-coarse:    libc: 17 nsec/call
> clock-gettime-monotonic-coarse:    vdso: 11 nsec/call
> 
> CC: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Signed-off-by: Santosh Sivaraj <santosh at fossix.org>
> ---
>  arch/powerpc/kernel/asm-offsets.c         |  2 +
>  arch/powerpc/kernel/vdso64/gettimeofday.S | 67 ++++++++++++++++++++++++++-----
>  2 files changed, 58 insertions(+), 11 deletions(-)

... and no changes since the last rev?

It is better to post new versions in a separate thread and to include 
the changelog for easier review.


- Naveen