Re: [PATCH v6 00/19] Unify vDSOs across more architectures

[Shijith Thotton]

Hi Vincenzo,

On 5/30/19 7:15 AM, Vincenzo Frascino wrote:
> vDSO (virtual dynamic shared object) is a mechanism that the Linux
> kernel provides as an alternative to system calls to reduce where
> possible the costs in terms of cycles.
> This is possible because certain syscalls like gettimeofday() do
> not write any data and return one or more values that are stored
> in the kernel, which makes relatively safe calling them directly
> as a library function.
> 
> Even if the mechanism is pretty much standard, every architecture
> in the last few years ended up implementing their own vDSO library
> in the architectural code.
> 
> The purpose of this patch-set is to identify the commonalities in
> between the architectures and try to consolidate the common code
> paths, starting with gettimeofday().
> 
> This implementation contains the following design choices:
>   * Every architecture defines the arch specific code in an header in
>     "asm/vdso/".
>   * The generic implementation includes the arch specific one and lives
>     in "lib/vdso".
>   * The arch specific code for gettimeofday lives in
>     "<arch path>/vdso/gettimeofday.c" and includes the generic code only.
>   * The generic implementation of update_vsyscall and update_vsyscall_tz
>     lives in kernel/vdso and provide the bindings that can be implemented
>     by each architecture.
>   * Each architecture provides its implementation of the bindings in
>     "asm/vdso/vsyscall.h".
>   * This approach allows to consolidate the common code in a single place
>     with the benefit of avoiding code duplication.
> 
> This implementation contains the portings to the common library for: arm64,
> compat mode for arm64, arm, mips, x86_64, x32, compat mode for x86_64 and
> i386.
> 
> The mips porting has been tested on qemu for mips32el. A configuration to
> repeat the tests can be found at [4].
> 
> The x86_64 porting has been tested on an Intel Xeon 5120T based machine
> running Ubuntu 18.04 and using the Ubuntu provided defconfig.
> 
> The i386 porting has been tested on qemu using the i386_defconfig
> configuration.
> 
> Last but not least from this porting arm64, compat arm64, arm and mips gain
> the support for:
>   * CLOCK_BOOTTIME that can be useful in certain scenarios since it keeps
>     track of the time during sleep as well.
>   * CLOCK_TAI that is like CLOCK_REALTIME, but uses the International
>     Atomic Time (TAI) reference instead of UTC to avoid jumping on leap
>     second updates.
> for both clock_gettime and clock_getres.
> 
> The porting has been validated using the vdsotest test-suite [1] extended
> to cover all the clock ids [2].
> 
> A new test has been added to the linux kselftest in order to validate the
> newly added library.
> 
> The porting has been benchmarked and the performance results are
> provided as part of this cover letter.
> 
> To simplify the testing, a copy of the patchset on top of a recent linux
> tree can be found at [3] and [4].
> 
> [1] https://github.com/nathanlynch/vdsotest
> [2] https://github.com/fvincenzo/vdsotest
> [3] git://linux-arm.org/linux-vf.git vdso/v6
> [4] git://linux-arm.org/linux-vf.git vdso-mips/v6
> 
> Changes:
> --------
> v6:
>    - Rebased on 5.2-rc2.
>    - Added performance numbers.
>    - Removed vdso_types.h.
>    - Unified update_vsyscall and update_vsyscall_tz.
>    - Reworked the kselftest included in this patchset.
>    - Addressed review comments.
> v5:
>    - Rebased on 5.0-rc7.
>    - Added x86_64, compat mode for x86_64 and i386 portings.
>    - Extended vDSO kselftest.
>    - Addressed review comments.
> v4:
>    - Rebased on 5.0-rc2.
>    - Addressed review comments.
>    - Disabled compat vdso on arm64 when the kernel is compiled with
>      clang.
> v3:
>    - Ported the latest fixes and optimizations done on the x86
>      architecture to the generic library.
>    - Addressed review comments.
>    - Improved the documentation of the interfaces.
>    - Changed the HAVE_ARCH_TIMER config option to a more generic
>      HAVE_HW_COUNTER.
> v2:
>    - Added -ffixed-x18 to arm64
>    - Repleced occurrences of timeval and timespec
>    - Modified datapage.h to be compliant with y2038 on all the architectures
>    - Removed __u_vdso type
> 
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Paul Burton <paul.burton@xxxxxxxx>
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
> Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
> Cc: Shuah Khan <shuah@xxxxxxxxxx>
> Cc: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
> Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> Cc: Huw Davies <huw@xxxxxxxxxxxxxxx>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> 
> Performance Numbers: Linux 5.2.0-rc2 - Xeon Gold 5120T
> ======================================================
> 
> Unified vDSO:
> -------------
> 
> clock-gettime-monotonic: syscall: 342 nsec/call
> clock-gettime-monotonic:    libc: 25 nsec/call
> clock-gettime-monotonic:    vdso: 24 nsec/call
> clock-getres-monotonic: syscall: 296 nsec/call
> clock-getres-monotonic:    libc: 296 nsec/call
> clock-getres-monotonic:    vdso: 3 nsec/call
> clock-gettime-monotonic-coarse: syscall: 294 nsec/call
> clock-gettime-monotonic-coarse:    libc: 5 nsec/call
> clock-gettime-monotonic-coarse:    vdso: 5 nsec/call
> clock-getres-monotonic-coarse: syscall: 295 nsec/call
> clock-getres-monotonic-coarse:    libc: 292 nsec/call
> clock-getres-monotonic-coarse:    vdso: 5 nsec/call
> clock-gettime-monotonic-raw: syscall: 343 nsec/call
> clock-gettime-monotonic-raw:    libc: 25 nsec/call
> clock-gettime-monotonic-raw:    vdso: 23 nsec/call
> clock-getres-monotonic-raw: syscall: 290 nsec/call
> clock-getres-monotonic-raw:    libc: 290 nsec/call
> clock-getres-monotonic-raw:    vdso: 4 nsec/call
> clock-gettime-tai: syscall: 332 nsec/call
> clock-gettime-tai:    libc: 24 nsec/call
> clock-gettime-tai:    vdso: 23 nsec/call
> clock-getres-tai: syscall: 288 nsec/call
> clock-getres-tai:    libc: 288 nsec/call
> clock-getres-tai:    vdso: 3 nsec/call
> clock-gettime-boottime: syscall: 342 nsec/call
> clock-gettime-boottime:    libc: 24 nsec/call
> clock-gettime-boottime:    vdso: 23 nsec/call
> clock-getres-boottime: syscall: 284 nsec/call
> clock-getres-boottime:    libc: 291 nsec/call
> clock-getres-boottime:    vdso: 3 nsec/call
> clock-gettime-realtime: syscall: 337 nsec/call
> clock-gettime-realtime:    libc: 24 nsec/call
> clock-gettime-realtime:    vdso: 23 nsec/call
> clock-getres-realtime: syscall: 287 nsec/call
> clock-getres-realtime:    libc: 284 nsec/call
> clock-getres-realtime:    vdso: 3 nsec/call
> clock-gettime-realtime-coarse: syscall: 307 nsec/call
> clock-gettime-realtime-coarse:    libc: 4 nsec/call
> clock-gettime-realtime-coarse:    vdso: 4 nsec/call
> clock-getres-realtime-coarse: syscall: 294 nsec/call
> clock-getres-realtime-coarse:    libc: 291 nsec/call
> clock-getres-realtime-coarse:    vdso: 4 nsec/call
> getcpu: syscall: 246 nsec/call
> getcpu:    libc: 14 nsec/call
> getcpu:    vdso: 11 nsec/call
> gettimeofday: syscall: 293 nsec/call
> gettimeofday:    libc: 26 nsec/call
> gettimeofday:    vdso: 25 nsec/call
> 
> Stock Kernel:
> -------------
> 
> clock-gettime-monotonic: syscall: 338 nsec/call
> clock-gettime-monotonic:    libc: 24 nsec/call
> clock-gettime-monotonic:    vdso: 23 nsec/call
> clock-getres-monotonic: syscall: 291 nsec/call
> clock-getres-monotonic:    libc: 304 nsec/call
> clock-getres-monotonic:    vdso: not tested
> Note: vDSO version of clock_getres not found
> clock-gettime-monotonic-coarse: syscall: 297 nsec/call
> clock-gettime-monotonic-coarse:    libc: 5 nsec/call
> clock-gettime-monotonic-coarse:    vdso: 4 nsec/call
> clock-getres-monotonic-coarse: syscall: 281 nsec/call
> clock-getres-monotonic-coarse:    libc: 286 nsec/call
> clock-getres-monotonic-coarse:    vdso: not tested
> Note: vDSO version of clock_getres not found
> clock-gettime-monotonic-raw: syscall: 336 nsec/call
> clock-gettime-monotonic-raw:    libc: 340 nsec/call
> clock-gettime-monotonic-raw:    vdso: 346 nsec/call
> clock-getres-monotonic-raw: syscall: 297 nsec/call
> clock-getres-monotonic-raw:    libc: 301 nsec/call
> clock-getres-monotonic-raw:    vdso: not tested
> Note: vDSO version of clock_getres not found
> clock-gettime-tai: syscall: 351 nsec/call
> clock-gettime-tai:    libc: 24 nsec/call
> clock-gettime-tai:    vdso: 23 nsec/call
> clock-getres-tai: syscall: 298 nsec/call
> clock-getres-tai:    libc: 290 nsec/call
> clock-getres-tai:    vdso: not tested
> Note: vDSO version of clock_getres not found
> clock-gettime-boottime: syscall: 342 nsec/call
> clock-gettime-boottime:    libc: 347 nsec/call
> clock-gettime-boottime:    vdso: 355 nsec/call
> clock-getres-boottime: syscall: 296 nsec/call
> clock-getres-boottime:    libc: 295 nsec/call
> clock-getres-boottime:    vdso: not tested
> Note: vDSO version of clock_getres not found
> clock-gettime-realtime: syscall: 346 nsec/call
> clock-gettime-realtime:    libc: 24 nsec/call
> clock-gettime-realtime:    vdso: 22 nsec/call
> clock-getres-realtime: syscall: 295 nsec/call
> clock-getres-realtime:    libc: 291 nsec/call
> clock-getres-realtime:    vdso: not tested
> Note: vDSO version of clock_getres not found
> clock-gettime-realtime-coarse: syscall: 292 nsec/call
> clock-gettime-realtime-coarse:    libc: 5 nsec/call
> clock-gettime-realtime-coarse:    vdso: 4 nsec/call
> clock-getres-realtime-coarse: syscall: 300 nsec/call
> clock-getres-realtime-coarse:    libc: 301 nsec/call
> clock-getres-realtime-coarse:    vdso: not tested
> Note: vDSO version of clock_getres not found
> getcpu: syscall: 252 nsec/call
> getcpu:    libc: 14 nsec/call
> getcpu:    vdso: 11 nsec/call
> gettimeofday: syscall: 293 nsec/call
> gettimeofday:    libc: 24 nsec/call
> gettimeofday:    vdso: 25 nsec/call
> 
> 
> Peter Collingbourne (1):
>    arm64: Build vDSO with -ffixed-x18
> 
> Vincenzo Frascino (18):
>    kernel: Standardize vdso_datapage
>    kernel: Define gettimeofday vdso common code
>    kernel: Unify update_vsyscall implementation
>    arm64: Substitute gettimeofday with C implementation
>    arm64: compat: Add missing syscall numbers
>    arm64: compat: Expose signal related structures
>    arm64: compat: Generate asm offsets for signals
>    lib: vdso: Add compat support
>    arm64: compat: Add vDSO
>    arm64: Refactor vDSO code
>    arm64: compat: vDSO setup for compat layer
>    arm64: elf: vDSO code page discovery
>    arm64: compat: Get sigreturn trampolines from vDSO
>    arm64: Add vDSO compat support
>    arm: Add support for generic vDSO
>    mips: Add support for generic vDSO
>    x86: Add support for generic vDSO
>    kselftest: Extend vDSO selftest
> 
>   arch/arm/Kconfig                              |   3 +
>   arch/arm/include/asm/vdso/gettimeofday.h      |  96 +++++
>   arch/arm/include/asm/vdso/vsyscall.h          |  71 ++++
>   arch/arm/include/asm/vdso_datapage.h          |  29 +-
>   arch/arm/kernel/vdso.c                        |  87 +----
>   arch/arm/vdso/Makefile                        |  13 +-
>   arch/arm/vdso/note.c                          |  15 +
>   arch/arm/vdso/vdso.lds.S                      |   2 +
>   arch/arm/vdso/vgettimeofday.c                 | 268 +------------
>   arch/arm64/Kconfig                            |   3 +
>   arch/arm64/Makefile                           |  23 +-
>   arch/arm64/include/asm/elf.h                  |  14 +
>   arch/arm64/include/asm/signal32.h             |  46 +++
>   arch/arm64/include/asm/unistd.h               |   5 +
>   arch/arm64/include/asm/vdso.h                 |   3 +
>   arch/arm64/include/asm/vdso/compat_barrier.h  |  51 +++
>   .../include/asm/vdso/compat_gettimeofday.h    | 108 ++++++
>   arch/arm64/include/asm/vdso/gettimeofday.h    |  84 +++++
>   arch/arm64/include/asm/vdso/vsyscall.h        |  53 +++
>   arch/arm64/include/asm/vdso_datapage.h        |  48 ---
>   arch/arm64/kernel/Makefile                    |   6 +-
>   arch/arm64/kernel/asm-offsets.c               |  39 +-
>   arch/arm64/kernel/signal32.c                  |  72 ++--
>   arch/arm64/kernel/vdso.c                      | 356 ++++++++++++------
>   arch/arm64/kernel/vdso/Makefile               |  34 +-
>   arch/arm64/kernel/vdso/gettimeofday.S         | 334 ----------------
>   arch/arm64/kernel/vdso/vgettimeofday.c        |  28 ++
>   arch/arm64/kernel/vdso32/.gitignore           |   2 +
>   arch/arm64/kernel/vdso32/Makefile             | 184 +++++++++
>   arch/arm64/kernel/vdso32/note.c               |  15 +
>   arch/arm64/kernel/vdso32/sigreturn.S          |  62 +++
>   arch/arm64/kernel/vdso32/vdso.S               |  19 +
>   arch/arm64/kernel/vdso32/vdso.lds.S           |  82 ++++
>   arch/arm64/kernel/vdso32/vgettimeofday.c      |  59 +++
>   arch/mips/Kconfig                             |   2 +
>   arch/mips/include/asm/vdso.h                  |  78 +---
>   arch/mips/include/asm/vdso/gettimeofday.h     | 175 +++++++++
>   arch/mips/{ => include/asm}/vdso/vdso.h       |   6 +-
>   arch/mips/include/asm/vdso/vsyscall.h         |  43 +++
>   arch/mips/kernel/vdso.c                       |  37 +-
>   arch/mips/vdso/Makefile                       |  25 +-
>   arch/mips/vdso/elf.S                          |   2 +-
>   arch/mips/vdso/gettimeofday.c                 | 273 --------------
>   arch/mips/vdso/sigreturn.S                    |   2 +-
>   arch/mips/vdso/vdso.lds.S                     |   4 +
>   arch/mips/vdso/vgettimeofday.c                |  57 +++
>   arch/x86/Kconfig                              |   3 +
>   arch/x86/entry/vdso/Makefile                  |   9 +
>   arch/x86/entry/vdso/vclock_gettime.c          | 251 +++---------
>   arch/x86/entry/vdso/vdso.lds.S                |   2 +
>   arch/x86/entry/vdso/vdso32/vdso32.lds.S       |   2 +
>   arch/x86/entry/vdso/vdsox32.lds.S             |   1 +
>   arch/x86/entry/vsyscall/Makefile              |   2 -
>   arch/x86/entry/vsyscall/vsyscall_gtod.c       |  83 ----
>   arch/x86/include/asm/mshyperv-tsc.h           |  76 ++++
>   arch/x86/include/asm/mshyperv.h               |  70 +---
>   arch/x86/include/asm/pvclock.h                |   2 +-
>   arch/x86/include/asm/vdso/gettimeofday.h      | 203 ++++++++++
>   arch/x86/include/asm/vdso/vsyscall.h          |  44 +++
>   arch/x86/include/asm/vgtod.h                  |  75 +---
>   arch/x86/include/asm/vvar.h                   |   7 +-
>   arch/x86/kernel/pvclock.c                     |   1 +
>   include/asm-generic/vdso/vsyscall.h           |  56 +++
>   include/linux/hrtimer.h                       |  15 +-
>   include/linux/hrtimer_defs.h                  |  25 ++
>   include/linux/timekeeper_internal.h           |   9 +
>   include/vdso/datapage.h                       |  91 +++++
>   include/vdso/helpers.h                        |  56 +++
>   include/vdso/vsyscall.h                       |  11 +
>   kernel/Makefile                               |   1 +
>   kernel/vdso/Makefile                          |   2 +
>   kernel/vdso/vsyscall.c                        | 139 +++++++
>   lib/Kconfig                                   |   5 +
>   lib/vdso/Kconfig                              |  36 ++
>   lib/vdso/Makefile                             |  22 ++
>   lib/vdso/gettimeofday.c                       | 229 +++++++++++
>   tools/testing/selftests/vDSO/Makefile         |   2 +
>   tools/testing/selftests/vDSO/vdso_full_test.c | 261 +++++++++++++
>   78 files changed, 3042 insertions(+), 1767 deletions(-)
>   create mode 100644 arch/arm/include/asm/vdso/gettimeofday.h
>   create mode 100644 arch/arm/include/asm/vdso/vsyscall.h
>   create mode 100644 arch/arm/vdso/note.c
>   create mode 100644 arch/arm64/include/asm/vdso/compat_barrier.h
>   create mode 100644 arch/arm64/include/asm/vdso/compat_gettimeofday.h
>   create mode 100644 arch/arm64/include/asm/vdso/gettimeofday.h
>   create mode 100644 arch/arm64/include/asm/vdso/vsyscall.h
>   delete mode 100644 arch/arm64/include/asm/vdso_datapage.h
>   delete mode 100644 arch/arm64/kernel/vdso/gettimeofday.S
>   create mode 100644 arch/arm64/kernel/vdso/vgettimeofday.c
>   create mode 100644 arch/arm64/kernel/vdso32/.gitignore
>   create mode 100644 arch/arm64/kernel/vdso32/Makefile
>   create mode 100644 arch/arm64/kernel/vdso32/note.c
>   create mode 100644 arch/arm64/kernel/vdso32/sigreturn.S
>   create mode 100644 arch/arm64/kernel/vdso32/vdso.S
>   create mode 100644 arch/arm64/kernel/vdso32/vdso.lds.S
>   create mode 100644 arch/arm64/kernel/vdso32/vgettimeofday.c
>   create mode 100644 arch/mips/include/asm/vdso/gettimeofday.h
>   rename arch/mips/{ => include/asm}/vdso/vdso.h (90%)
>   create mode 100644 arch/mips/include/asm/vdso/vsyscall.h
>   delete mode 100644 arch/mips/vdso/gettimeofday.c
>   create mode 100644 arch/mips/vdso/vgettimeofday.c
>   delete mode 100644 arch/x86/entry/vsyscall/vsyscall_gtod.c
>   create mode 100644 arch/x86/include/asm/mshyperv-tsc.h
>   create mode 100644 arch/x86/include/asm/vdso/gettimeofday.h
>   create mode 100644 arch/x86/include/asm/vdso/vsyscall.h
>   create mode 100644 include/asm-generic/vdso/vsyscall.h
>   create mode 100644 include/linux/hrtimer_defs.h
>   create mode 100644 include/vdso/datapage.h
>   create mode 100644 include/vdso/helpers.h
>   create mode 100644 include/vdso/vsyscall.h
>   create mode 100644 kernel/vdso/Makefile
>   create mode 100644 kernel/vdso/vsyscall.c
>   create mode 100644 lib/vdso/Kconfig
>   create mode 100644 lib/vdso/Makefile
>   create mode 100644 lib/vdso/gettimeofday.c
>   create mode 100644 tools/testing/selftests/vDSO/vdso_full_test.c
> 

Ran vdsotest-bench on ThunderX2 (arm64) with and without unified 
patchset. The numbers are as below:

Unified vDSO:
-------------
clock-gettime-monotonic: syscall: 346 nsec/call
clock-gettime-monotonic:    libc: 38 nsec/call
clock-gettime-monotonic:    vdso: 36 nsec/call
clock-getres-monotonic: syscall: 262 nsec/call
clock-getres-monotonic:    libc: 6 nsec/call
clock-getres-monotonic:    vdso: 5 nsec/call
clock-gettime-monotonic-coarse: syscall: 296 nsec/call
clock-gettime-monotonic-coarse:    libc: 39 nsec/call
clock-gettime-monotonic-coarse:    vdso: 38 nsec/call
clock-getres-monotonic-coarse: syscall: 260 nsec/call
clock-getres-monotonic-coarse:    libc: 8 nsec/call
clock-getres-monotonic-coarse:    vdso: 5 nsec/call
clock-gettime-monotonic-raw: syscall: 345 nsec/call
clock-gettime-monotonic-raw:    libc: 35 nsec/call
clock-gettime-monotonic-raw:    vdso: 34 nsec/call
clock-getres-monotonic-raw: syscall: 261 nsec/call
clock-getres-monotonic-raw:    libc: 7 nsec/call
clock-getres-monotonic-raw:    vdso: 5 nsec/call
clock-gettime-tai: syscall: 357 nsec/call
clock-gettime-tai:    libc: 38 nsec/call
clock-gettime-tai:    vdso: 36 nsec/call
clock-getres-tai: syscall: 257 nsec/call
clock-getres-tai:    libc: 7 nsec/call
clock-getres-tai:    vdso: 5 nsec/call
clock-gettime-boottime: syscall: 356 nsec/call
clock-gettime-boottime:    libc: 38 nsec/call
clock-gettime-boottime:    vdso: 36 nsec/call
clock-getres-boottime: syscall: 257 nsec/call
clock-getres-boottime:    libc: 6 nsec/call
clock-getres-boottime:    vdso: 5 nsec/call
clock-gettime-realtime: syscall: 345 nsec/call
clock-gettime-realtime:    libc: 38 nsec/call
clock-gettime-realtime:    vdso: 36 nsec/call
clock-getres-realtime: syscall: 257 nsec/call
clock-getres-realtime:    libc: 7 nsec/call
clock-getres-realtime:    vdso: 5 nsec/call
clock-gettime-realtime-coarse: syscall: 295 nsec/call
clock-gettime-realtime-coarse:    libc: 39 nsec/call
clock-gettime-realtime-coarse:    vdso: 38 nsec/call
clock-getres-realtime-coarse: syscall: 260 nsec/call
clock-getres-realtime-coarse:    libc: 8 nsec/call
clock-getres-realtime-coarse:    vdso: 5 nsec/call
getcpu: syscall: 244 nsec/call
getcpu:    libc: 247 nsec/call
getcpu:    vdso: not tested
Note: vDSO version of getcpu not found
gettimeofday: syscall: 383 nsec/call
gettimeofday:    libc: 39 nsec/call
gettimeofday:    vdso: 35 nsec/call

Stock Kernel:
-------------
clock-gettime-monotonic: syscall: 344 nsec/call
clock-gettime-monotonic:    libc: 74 nsec/call
clock-gettime-monotonic:    vdso: 73 nsec/call
clock-getres-monotonic: syscall: 258 nsec/call
clock-getres-monotonic:    libc: 6 nsec/call
clock-getres-monotonic:    vdso: 4 nsec/call
clock-gettime-monotonic-coarse: syscall: 300 nsec/call
clock-gettime-monotonic-coarse:    libc: 36 nsec/call
clock-gettime-monotonic-coarse:    vdso: 34 nsec/call
clock-getres-monotonic-coarse: syscall: 261 nsec/call
clock-getres-monotonic-coarse:    libc: 6 nsec/call
clock-getres-monotonic-coarse:    vdso: 4 nsec/call
clock-gettime-monotonic-raw: syscall: 346 nsec/call
clock-gettime-monotonic-raw:    libc: 74 nsec/call
clock-gettime-monotonic-raw:    vdso: 72 nsec/call
clock-getres-monotonic-raw: syscall: 254 nsec/call
clock-getres-monotonic-raw:    libc: 6 nsec/call
clock-getres-monotonic-raw:    vdso: 4 nsec/call
clock-gettime-tai: syscall: 345 nsec/call
clock-gettime-tai:    libc: 361 nsec/call
clock-gettime-tai:    vdso: 359 nsec/call
clock-getres-tai: syscall: 259 nsec/call
clock-getres-tai:    libc: 262 nsec/call
clock-getres-tai:    vdso: 258 nsec/call
clock-gettime-boottime: syscall: 353 nsec/call
clock-gettime-boottime:    libc: 365 nsec/call
clock-gettime-boottime:    vdso: 362 nsec/call
clock-getres-boottime: syscall: 260 nsec/call
clock-getres-boottime:    libc: 267 nsec/call
clock-getres-boottime:    vdso: 259 nsec/call
clock-gettime-realtime: syscall: 344 nsec/call
clock-gettime-realtime:    libc: 73 nsec/call
clock-gettime-realtime:    vdso: 72 nsec/call
clock-getres-realtime: syscall: 255 nsec/call
clock-getres-realtime:    libc: 7 nsec/call
clock-getres-realtime:    vdso: 4 nsec/call
clock-gettime-realtime-coarse: syscall: 296 nsec/call
clock-gettime-realtime-coarse:    libc: 35 nsec/call
clock-gettime-realtime-coarse:    vdso: 33 nsec/call
clock-getres-realtime-coarse: syscall: 258 nsec/call
clock-getres-realtime-coarse:    libc: 6 nsec/call
clock-getres-realtime-coarse:    vdso: 4 nsec/call
getcpu: syscall: 237 nsec/call
getcpu:    libc: 242 nsec/call
getcpu:    vdso: not tested
Note: vDSO version of getcpu not found
gettimeofday: syscall: 378 nsec/call
gettimeofday:    libc: 73 nsec/call
gettimeofday:    vdso: 70 nsec/call

Observed good improvement for some APIs with the patch.

Tested-by: Shijith Thotton <sthotton@xxxxxxxxxxx>

Thanks,
Shijith