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platform_bionic/libc/private
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Mark Salyzyn 4473ccd5b0 bionic: add vdso time() 
time() can be a hot call, and it currently uses __vdso_gettimeofday,
which is already pretty fast (~3 times faster than the syscall),
but with a __vdso_time call it is ~3 times even faster, in part
because __vdso_time does not require interlocking with updates,
and the read for just the seconds is atomic.  __vdso_time is
always available, whereas __vdso_gettimeofday is gated on access
to the physical timers.  arm improvement is compelling (x10),
x86 improvement is even more pronounced (x100).

[TL;DR]

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

BEFORE:

hikey960 vdso (aarch64):

----------------------------------------------------------------------
Benchmark                               Time           CPU Iterations
----------------------------------------------------------------------
BM_time_clock_gettime                  48 ns         48 ns   15414753
BM_time_clock_gettime_syscall         175 ns        175 ns    4062031
BM_time_clock_gettime_REALTIME         44 ns         44 ns   15897875
BM_time_clock_gettime_BOOTTIME         47 ns         47 ns   14307903
BM_time_clock_gettime_TAI             210 ns        210 ns    3341372
BM_time_clock_gettime_unsupported     100 ns        100 ns    7030649
BM_time_gettimeofday                   47 ns         47 ns   14969643
BM_time_gettimeofday_syscall          163 ns        163 ns    4283542
BM_time_time                           59 ns         59 ns   11815385

hikey960 vdso32 (aarch32):

----------------------------------------------------------------------
Benchmark                               Time           CPU Iterations
----------------------------------------------------------------------
BM_time_clock_gettime                  90 ns         90 ns    7572898
BM_time_clock_gettime_syscall         251 ns        251 ns    2763442
BM_time_clock_gettime_REALTIME         81 ns         80 ns    8699536
BM_time_clock_gettime_BOOTTIME         97 ns         97 ns    7256667
BM_time_clock_gettime_TAI             272 ns        272 ns    2570419
BM_time_clock_gettime_unsupported     160 ns        160 ns    4379819
BM_time_gettimeofday                   73 ns         73 ns    9608922
BM_time_gettimeofday_syscall          200 ns        199 ns    3527957
BM_time_time                          123 ns        123 ns    5651095

x86_64 (glibc):

--------------------------------------------------------------------
Benchmark                             Time           CPU Iterations
--------------------------------------------------------------------
BM_time_clock_gettime                  21 ns         21 ns   28873070
BM_time_clock_gettime_syscall         224 ns        224 ns    3095370
BM_time_clock_gettime_REALTIME         17 ns         17 ns   42083086
BM_time_clock_gettime_BOOTTIME        239 ns        239 ns    2924015
BM_time_clock_gettime_TAI             236 ns        236 ns    2961423
BM_time_clock_gettime_unsupported     221 ns        221 ns    3357696
BM_time_gettimeofday                 22 ns         22 ns   27975154
BM_time_gettimeofday_syscall        238 ns        238 ns    2882032
BM_time_time                          2 ns          2 ns  340354885
BM_time_time_syscall                207 ns        207 ns    3383073

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

Benchmark                           Time(ns)    CPU(ns) Iterations
------------------------------------------------------------------
BM_time_clock_gettime                     20        477    1489362
BM_time_clock_gettime_syscall             20        487    1458333
BM_time_clock_gettime_REALTIME            19        464    1400000
BM_time_clock_gettime_BOOTTIME            29        700    1000000
BM_time_clock_gettime_TAI                 29        690    1000000
BM_time_clock_gettime_unsupported          9        227    3043478
BM_time_gettimeofday                      18        444    1555556
BM_time_gettimeofday_syscall              19        456    1555556
BM_time_time                              21        497    1166667

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

Benchmark                           Time(ns)    CPU(ns) Iterations
------------------------------------------------------------------
BM_time_clock_gettime                      6        144    4666667
BM_time_clock_gettime_syscall             20        486    1400000
BM_time_clock_gettime_REALTIME             6        136    5000000
BM_time_clock_gettime_BOOTTIME             6        153    4375000
BM_time_clock_gettime_TAI                 31        760    1000000
BM_time_clock_gettime_unsupported         10        233    3043478
BM_time_gettimeofday                       6        140    5000000
BM_time_gettimeofday_syscall              19        450    1555556
BM_time_time                               9        203    3500000

AFTER:

hikey960 vdso (aarch64):

--------------------------------------------------------------------
Benchmark                             Time           CPU Iterations
--------------------------------------------------------------------
BM_time_clock_gettime                48 ns         48 ns   15414753
BM_time_clock_gettime_syscall       175 ns        175 ns    4062031
BM_time_clock_gettime_REALTIME       44 ns         44 ns   15897875
BM_time_clock_gettime_BOOTTIME       47 ns         47 ns   14307903
BM_time_clock_gettime_TAI           210 ns        210 ns    3341372
BM_time_clock_gettime_unsupported   100 ns        100 ns    7030649
BM_time_gettimeofday                 47 ns         47 ns   14975314
BM_time_gettimeofday_syscall        164 ns        164 ns    4278797
BM_time_time                         16 ns         16 ns   42932165

hikey960 vdso32 (aarch32):

--------------------------------------------------------------------
Benchmark                             Time           CPU Iterations
--------------------------------------------------------------------
BM_time_clock_gettime                90 ns         90 ns    7572898
BM_time_clock_gettime_syscall       251 ns        251 ns    2763442
BM_time_clock_gettime_REALTIME       81 ns         80 ns    8699536
BM_time_clock_gettime_BOOTTIME       97 ns         97 ns    7256667
BM_time_clock_gettime_TAI           272 ns        272 ns    2570419
BM_time_clock_gettime_unsupported   160 ns        160 ns    4379819
BM_time_gettimeofday                 73 ns         73 ns    9596230
BM_time_gettimeofday_syscall        199 ns        199 ns    3575428
BM_time_time                         35 ns         35 ns   19798801

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

Benchmark                           Time(ns)    CPU(ns) Iterations
------------------------------------------------------------------
BM_time_clock_gettime                     20        477    1489362
BM_time_clock_gettime_syscall             20        487    1458333
BM_time_clock_gettime_REALTIME            19        464    1400000
BM_time_clock_gettime_BOOTTIME            29        700    1000000
BM_time_clock_gettime_TAI                 29        690    1000000
BM_time_clock_gettime_unsupported          9        227    3043478
BM_time_gettimeofday                      18        444    1555556
BM_time_gettimeofday_syscall              19        456    1555556
BM_time_time                               2         50   11666667

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

Benchmark                           Time(ns)    CPU(ns) Iterations
------------------------------------------------------------------
BM_time_clock_gettime                      6        144    4666667
BM_time_clock_gettime_syscall             20        486    1400000
BM_time_clock_gettime_REALTIME             6        136    5000000
BM_time_clock_gettime_BOOTTIME             6        153    4375000
BM_time_clock_gettime_TAI                 31        760    1000000
BM_time_clock_gettime_unsupported         10        233    3043478
BM_time_gettimeofday                       6        140    5000000
BM_time_gettimeofday_syscall              19        450    1555556
BM_time_time                               2         50   10000000

Test: bionic-unit-tests --gtest_filter=time.time
      taskset F bionic-benchmarks --bionic_xml=vdso.xml \
          --benchmark_filter='BM_time_(time*|clock_gettime*|gettimeofday*)'
Bug: 63737556
Change-Id: I81b088a12ca41a6c4733d46c5477527777138efa
2018-01-11 15:46:11 +00:00
..
__get_tls.h AArch64: Add initial support for AArch64 2013-12-16 17:00:22 -08:00
bionic_arc4random.h Add __libc_arc4random_unlimited_entropy. 2016-11-29 15:26:08 -08:00
bionic_asm.h Mark __BIONIC_WEAK_FOR_NATIVE_BRIDGE symbols 2017-10-27 10:01:46 +02:00
bionic_asm_arm.h Unified sysroot: kill arch-specific include dirs. 2017-10-12 13:19:51 -07:00
bionic_asm_arm64.h Unified sysroot: kill arch-specific include dirs. 2017-10-12 13:19:51 -07:00
bionic_asm_mips.h Unified sysroot: kill arch-specific include dirs. 2017-10-12 13:19:51 -07:00
bionic_asm_x86.h Unified sysroot: kill arch-specific include dirs. 2017-10-12 13:19:51 -07:00
bionic_asm_x86_64.h Unified sysroot: kill arch-specific include dirs. 2017-10-12 13:19:51 -07:00
bionic_auxv.h Switch <elf.h> over to linux uapi under the covers. 2014-02-10 18:22:24 -08:00
bionic_config.h Use a separate config.h for config like defines. 2014-06-16 23:35:53 -07:00
bionic_constants.h Add semaphore tests, fix sem_destroy. 2014-09-19 17:37:06 -07:00
bionic_ctype.h Use inline ctype functions for ato*/strto* and scanf. 2017-12-19 16:37:01 -08:00
bionic_defs.h Mark __BIONIC_WEAK_FOR_NATIVE_BRIDGE symbols 2017-10-27 10:01:46 +02:00
bionic_errdefs.h Move <sys/_sigdefs.h> and <sys/_errdefs.h> to private. 2016-04-13 17:45:39 -07:00
bionic_fortify.h Add null checks to <dirent.h> functions. 2017-10-26 16:16:33 -07:00
bionic_futex.h Always use CLOCK_MONOTONIC for pthreads and semaphores 2017-08-18 09:11:05 -07:00
bionic_globals.h Only initialize the global stack protector once. 2016-06-30 12:58:32 -07:00
bionic_ieee.h Fix instances of '#if __LP64__'. 2016-09-15 14:21:28 -07:00
bionic_lock.h Always use CLOCK_MONOTONIC for pthreads and semaphores 2017-08-18 09:11:05 -07:00
bionic_macros.h Only use uids and gids for which we've allocated AIDs 2017-11-15 10:31:49 -08:00
bionic_malloc_dispatch.h Add support for modifying decay timer. 2017-05-15 16:59:16 -07:00
bionic_mbstate.h Hide various mbstate implementation details. 2017-07-14 17:00:05 -07:00
bionic_page.h Move PAGE_MASK into <sys/user.h>. 2015-07-28 14:58:37 -07:00
bionic_prctl.h Label pages mapped by linker_allocator 2014-08-11 09:22:48 -07:00
bionic_sdk_version.h Revert "Revert "Make sem_wait able to return errno EINTR for sdk > 23."" 2016-01-25 17:39:18 -08:00
bionic_sigdefs.h Move <sys/_sigdefs.h> and <sys/_errdefs.h> to private. 2016-04-13 17:45:39 -07:00
bionic_ssp.h Simplify __stack_chk_fail, and fix it so we get debuggerd stack traces. 2013-02-14 14:37:34 -08:00
bionic_string_utils.h Fix pthread_getattr_np for the main thread. 2014-08-26 10:36:38 -07:00
bionic_systrace.h Add end() method to bionic's ScopedTrace class 2017-03-20 12:45:55 -07:00
bionic_time_conversions.h Always use CLOCK_MONOTONIC for pthreads and semaphores 2017-08-18 09:11:05 -07:00
bionic_tls.h Add a legacy inline for mmap64. 2017-10-05 23:41:47 -07:00
bionic_vdso.h bionic: add vdso time() 2018-01-11 15:46:11 +00:00
CachedProperty.h Update CachedProperty to support long ro. properties 2017-10-18 10:25:39 -07:00
CFIShadow.h Revert "Revert "arm64: expand CFI shadow to cover 48-bit virtual addresses"" 2017-08-03 14:11:28 -07:00
ErrnoRestorer.h Bring in google3-style DISALLOW_* macros. 2014-05-09 19:12:08 -07:00
FdPath.h Add POSIX fexecve. 2017-10-18 16:26:17 -07:00
get_cpu_count_from_string.h Fix the way to count online cpus. 2015-09-29 17:49:37 -07:00
grp_pwd.h Allocate thread local buffers in __init_tls. 2017-02-22 16:05:03 -08:00
icu.h Implement <iconv.h>. 2017-08-25 08:47:41 -07:00
kernel_sigset_t.h Move some pthread functions to signal.h. 2014-11-21 10:26:09 -08:00
KernelArgumentBlock.h Tidy up KernelArgumentBlock::getauxval. 2016-01-05 16:29:33 -08:00
NetdClientDispatch.h Mark sockets on creation (socket()) and accept4(). 2014-05-19 15:19:16 -07:00
ScopedPthreadMutexLocker.h Explicitly disallow default c-tor 2015-12-01 16:57:19 -08:00
ScopedReaddir.h Implement scandirat and scandirat64. 2015-10-27 13:47:36 -07:00
ScopedSignalBlocker.h Implement <spawn.h>. 2017-10-11 14:57:49 -07:00
thread_private.h Defer registration of the arc4random fork-detect handler. 2016-06-28 15:52:59 -07:00
WriteProtected.h Move libc_log code into libasync_safe. 2017-05-03 08:50:43 -07:00