On Thu, Oct 17, 2019 at 04:47:48PM -0700, Andrei Vagin wrote: > > In my table, the "before" column is actually for the upstream kernel > with the 18-th patch. Here is the table with the real "before" column: > > | before | with 18/33 | CONFIG_TIME_NS=n | host | inside timens > ------------------------------------------------------------------------------ > avg | 150331408 | 153345935 | 153588088 | 150816637 | 139192114 > ------------------------------------------------------------------------------ > diff % | 98 | 100 | 100.1 | 98.3 | 90.7 > ------------------------------------------------------------------------------ > stdev % | 0.3 | 0.09 | 0.15 | 0.25 | 0.13 > > If we compare numbers in "before", "host" and "inside timens" columns, we > see the same results that you had. clock_gettime() works with the > same performance in the host namespace and 7% slower in a time > namespace. > I played with this a bit more and I've found that we can speed up clock_gettime on 5% more if we mark do_hres and do_coarse as __always_inline. With the unlikely hint in vdso_read_begin and noinline for do_hres_timens and do_coarse_timens: 1..8 ok 1 host: clock: monotonic cycles: 155278332 ok 2 host: clock: monotonic-coarse cycles: 662067077 ok 3 host: clock: monotonic-raw cycles: 151218057 ok 4 host: clock: boottime cycles: 154907635 ok 5 ns: clock: monotonic cycles: 133100433 ok 6 host: clock: monotonic-coarse cycles: 444170219 ok 7 host: clock: monotonic-raw cycles: 129550178 ok 8 ns: clock: boottime cycles: 130167136 With __always_inline for do_hres and do_coarse: 1..8 ok 1 host: clock: monotonic cycles: 163691015 ok 2 host: clock: monotonic-coarse cycles: 641443397 ok 3 host: clock: monotonic-raw cycles: 163649270 ok 4 host: clock: boottime cycles: 163682242 ok 5 ns: clock: monotonic cycles: 138759212 ok 6 host: clock: monotonic-coarse cycles: 486149502 ok 7 host: clock: monotonic-raw cycles: 134801053 ok 8 ns: clock: boottime cycles: 138675460 # Pass 8 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0 With __always_inline for do_hres, do_coarse, do_hres_timens, do_coarse_timens: 1..8 ok 1 host: clock: monotonic cycles: 158984538 ok 2 host: clock: monotonic-coarse cycles: 594932695 ok 3 host: clock: monotonic-raw cycles: 157834511 ok 4 host: clock: boottime cycles: 158297691 ok 5 ns: clock: monotonic cycles: 148559612 ok 6 host: clock: monotonic-coarse cycles: 468505657 ok 7 host: clock: monotonic-raw cycles: 146366575 ok 8 ns: clock: boottime cycles: 148573015 # Pass 8 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0 Thanks, Andrei
