Vincenzo, On Wed, 27 Feb 2019, Vincenzo Frascino wrote: > > The clocksource array has two elements (CLOCKSOURCE_RAW, CLOCKSOURCE_MONO) and > the situation with my scheme should be the following: Oops. I misread the patch, but still... > u32 seq: + 0 > s32 clock_mode; + 4 > u64 cycle_last; + 8 > struct vdso_cs cs[2]; + 16 > struct vdso_ts basetime[VDSO_BASES]; + 48 > > which I agree makes still things a bit worse. > > It's easy enough to benchmark these implementations and without trying I'm > > pretty sure that you can see the performance drop nicely. Please do so next > > time and provide the numbers in the changelogs. > > > > I did run some benchmarks this morning to quantify the performance impact and > seems that using vdsotest[1] the difference in between a stock linux kernel > 5.0.0-rc7 and one that has unified vDSO, running on my x86 machine (Xeon Gold > 5120T), is below 1%. Please find the results below, I will add them as well to > the next changelog. I have some doubts about 1%. NEW STOCK clock-gettime-monotonic: vdso: 31 28 ~ 10% slower clock-gettime-realtime: vdso: 32 29 ~ 10% slower Thanks, tglx
