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b65d3e5f0f
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.
17 lines
362 B
Plaintext
17 lines
362 B
Plaintext
libc {
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GLIBC_2.4 {
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ioperm; iopl;
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inb; inw; inl;
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outb; outw; outl;
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}
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GLIBC_2.11 {
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fallocate64;
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}
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GLIBC_PRIVATE {
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# A copy of sigaction lives in libpthread, and needs these.
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__default_sa_restorer; __default_rt_sa_restorer;
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# nptl/pthread_cond_timedwait.c uses INTERNAL_VSYSCALL(clock_gettime).
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__vdso_clock_gettime;
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}
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}
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