On 2017/10/11 08:35AM, 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 <b...@kernel.crashing.org> > Signed-off-by: Santosh Sivaraj <sant...@fossix.org> > --- > Changelog: > v1: > - gettimeofday was moved from asm to C > - Coarse timer support addition > v2: > - Moved Syscall fallback from inline assembly back to its original place in > __kernel_clock_gettime > v3: > - Based on Ben's input, coarse timer support was added in assembly itself > - Dropped idea of conversion to C due to the vdso update_count variable > being optimized out in C > v4: > - Based on Naveen's comments restructured code to avoid a duplicate code > block > v5: > - Skip creating dependency for registers that are not used for > CLOCK_REALTIME_COARSE (Naveen) > - Reorder instructions to get proper dependency setup (Naveen) > > arch/powerpc/kernel/asm-offsets.c | 2 + > arch/powerpc/kernel/vdso64/gettimeofday.S | 68 > ++++++++++++++++++++++++++----- > 2 files changed, 59 insertions(+), 11 deletions(-)
Looks good to me. Reviewed-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
