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

* Naveen N. Rao [off-list ref] wrote (on 2017-10-11 07:04:43 +0000):

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

Nope, this is indeed v5, a typo :-(

On 2017/10/10 11:10PM, Santosh Sivaraj wrote:

quoted

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@kernel.crashing.org>
Signed-off-by: Santosh Sivaraj <redacted>
---
 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?

There is that one line change of label. But otherwise its the same.

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

Sure.

Thanks,
Santosh

- Naveen

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