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

Shijith Thotton
2019-06-20T06:18:39Z

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@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Burton <paul.burton@mips.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Mark Salyzyn <salyzyn@android.com>
> Cc: Peter Collingbourne <pcc@google.com>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Dmitry Safonov <0x7f454c46@gmail.com>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Cc: Huw Davies <huw@codeweavers.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
> 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@marvell.com>

Thanks,
Shijith