tree 6b7a479b3a82507a0070777d1be3e6fa73b78cc3
parent 6f9c35ded294ca7b0b8f9042f705cbfca1ec8518
author Mark Salyzyn <salyzyn@google.com> 1510071560 -0800
committer Mark Salyzyn <salyzyn@google.com> 1512668508 -0800

bionic: add vdso clock_getres

clock_getres() should not be a hot call, nevertheless it is
~6-7 times faster for supported clock ids if it uses
__vdso_clock_getres if available.  There is a 3% performance
penalty for unsupported clock ids via __vdso_clock_getres with
respect to a direct syscall.

[TL;DR]

w/vdso32 kernel patches, locked cores to MAX, little cores only.

BEFORE:

hikey960 vdso (aarch64):

----------------------------------------------------------------------
Benchmark                               Time           CPU Iterations
----------------------------------------------------------------------
BM_time_clock_getres                  126 ns        126 ns    5577874
BM_time_clock_getres_syscall          127 ns        127 ns    5505016
BM_time_clock_getres_REALTIME         126 ns        126 ns    5574682
BM_time_clock_getres_BOOTTIME         126 ns        126 ns    5575237
BM_time_clock_getres_TAI              126 ns        126 ns    5576810
BM_time_clock_getres_unsupported      128 ns        128 ns    5480189

hikey960 vdso32 (aarch32):

----------------------------------------------------------------------
Benchmark                               Time           CPU Iterations
----------------------------------------------------------------------
BM_time_clock_getres                  199 ns        199 ns    3508708
BM_time_clock_getres_syscall          220 ns        220 ns    3184676
BM_time_clock_getres_REALTIME         199 ns        199 ns    3509697
BM_time_clock_getres_BOOTTIME         199 ns        199 ns    3513551
BM_time_clock_getres_TAI              200 ns        199 ns    3512412
BM_time_clock_getres_unsupported      196 ns        196 ns    3575609

x86_64 (glibc):

---------------------------------------------------------------------
Benchmark                              Time           CPU Iterations
---------------------------------------------------------------------
BM_time_clock_getres                 252 ns        252 ns    2370263
BM_time_clock_getres_syscall         215 ns        215 ns    3287497
BM_time_clock_getres_REALTIME        214 ns        214 ns    3294228
BM_time_clock_getres_BOOTTIME        213 ns        213 ns    3277519
BM_time_clock_getres_TAI             213 ns        213 ns    3294991
BM_time_clock_getres_unsupported     206 ns        206 ns    3450654

imx7d_pico IOT nyc (w/arm,cpu-registers-not-fw-configured) (armv7a):
(Virtual Timers)

Benchmark                           Time(ns)    CPU(ns) Iterations
------------------------------------------------------------------
BM_time_clock_getres                      16        345    2000000
BM_time_clock_getres_syscall              16        339    2121212
BM_time_clock_getres_REALTIME             17        350    2058824
BM_time_clock_getres_BOOTTIME             17        345    2000000
BM_time_clock_getres_TAI                  16        350    2000000
BM_time_clock_getres_unsupported          13        284    2500000

AFTER:

hikey960 vdso (aarch64):

---------------------------------------------------------------------
Benchmark                              Time           CPU Iterations
---------------------------------------------------------------------
BM_time_clock_getres                  18 ns         18 ns   37880389
BM_time_clock_getres_syscall         127 ns        127 ns    5520029
BM_time_clock_getres_REALTIME         18 ns         18 ns   37879962
BM_time_clock_getres_BOOTTIME         19 ns         18 ns   37878361
BM_time_clock_getres_TAI             131 ns        131 ns    5368484
BM_time_clock_getres_unsupported      97 ns         97 ns    7182864

hikey960 vdso32 (aarch32):

---------------------------------------------------------------------
Benchmark                              Time           CPU Iterations
---------------------------------------------------------------------
BM_time_clock_getres                  36 ns         36 ns   19205240
BM_time_clock_getres_syscall         212 ns        212 ns    3297100
BM_time_clock_getres_REALTIME         36 ns         36 ns   19219109
BM_time_clock_getres_BOOTTIME         36 ns         36 ns   19222490
BM_time_clock_getres_TAI             206 ns        206 ns    3402868
BM_time_clock_getres_unsupported     159 ns        159 ns    4409492

imx7d_pico IOT nyc (wo/arm,cpu-registers-not-fw-configured) (armv7a):
(Physical Timers)

Benchmark                           Time(ns)    CPU(ns) Iterations
------------------------------------------------------------------
BM_time_clock_getres                       2         48   14000000
BM_time_clock_getres_syscall              14        335    2058824
BM_time_clock_getres_REALTIME              2         49   14583333
BM_time_clock_getres_BOOTTIME              2         48   14000000
BM_time_clock_getres_TAI                  14        350    2058824
BM_time_clock_getres_unsupported           8        203    3500000

Test: taskset F \
        /data/benchmarktest{64}/bionic-benchmarks/bionic-benchmarks \
        --bionic_xml=vdso.xml --benchmark_filter=BM_time_clock_getres*
Bug: 63737556
Change-Id: I80c0a5106625d76720287f715fcf145d2aad1705