diff options
| author | Nathan Lynch <nathan_lynch@codesourcery.com> | 2015-06-04 21:10:43 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-06-04 21:10:43 +0000 |
| commit | b65d3e5f0f452e86f81d21d59b065feeb31357be (patch) | |
| tree | 6ac6681b12e442b6d6fa73093ef0ad60811491d7 /ChangeLog | |
| parent | 34caaafd1ae38c9295325a1da491d75a92b205b0 (diff) | |
ARM: VDSO support
Beginning with the upcoming 4.1 release, Linux on a subset of 32-bit
ARM hardware will provide fast user-space implementations of the
following system calls:
- gettimeofday
- clock_gettime
The kernel implementation depends on the ARMv7 Generic Timers
Extension to accelerate these system calls. So CPUs such as
Cortex-A15 and -A7 benefit, while Cortex-A9, -A8, and pre-v7 CPUs do
not. On systems where the VDSO does not provide any speedup, the
kernel prevents the relevant symbol lookups from succeeding.
On OMAP5 (Cortex-A15) gettimeofday latency decreases from ~350ns to
~120ns. On BeagleBone Black (Cortex-A8) it goes from ~650ns to
~660ns, which to my mind is an acceptable cost.
Verified that no new test failures are introduced on kernels with and
without the VDSO.
* sysdeps/unix/sysv/linux/arm/Makefile: (sysdep_routines):
Include dl-vdso.
* sysdeps/unix/sysv/linux/arm/init-first.c: New file:
Use VDSO routines for gettimeofday, clock_gettime if
available.
* sysdeps/unix/sysv/linux/arm/libc-vdso.h: New file:
Declare VDSO symbols.
* sysdeps/unix/sysv/linux/arm/sysdep.h:
[HAVE_GETTIMEOFDAY_VSYSCALL]: Define.
[HAVE_CLOCK_GETTIME_VSYSCALL]: Define.
* sysdeps/unix/sysv/linux/arm/Versions: Add
__vdso_clock_gettime.
Diffstat (limited to 'ChangeLog')
| -rw-r--r-- | ChangeLog | 15 |
1 files changed, 15 insertions, 0 deletions
@@ -1,3 +1,18 @@ +2015-06-04 Nathan Lynch <nathan_lynch@codesourcery.com> + + * sysdeps/unix/sysv/linux/arm/Makefile: (sysdep_routines): + Include dl-vdso. + * sysdeps/unix/sysv/linux/arm/init-first.c: New file: + Use VDSO routines for gettimeofday, clock_gettime if + available. + * sysdeps/unix/sysv/linux/arm/libc-vdso.h: New file: + Declare VDSO symbols. + * sysdeps/unix/sysv/linux/arm/sysdep.h: + [HAVE_GETTIMEOFDAY_VSYSCALL]: Define. + [HAVE_CLOCK_GETTIME_VSYSCALL]: Define. + * sysdeps/unix/sysv/linux/arm/Versions: Add + __vdso_clock_gettime. + 2015-06-04 Adhemerval Zanella <adhemerval.zanella@linaro.org> * sysdeps/unix/sysv/linux/not-cancel.h (open_not_cancel): Rewrite to |