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| author | Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2020-07-06 10:21:31 +0200 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2020-07-06 10:21:32 +0200 |
| commit | 6e29cb3f61ff5432c78a1c84b0d9b123a350ab36 (patch) | |
| tree | 64123a1c9f0e8b7e6ef41f9910449065c6942022 | |
| parent | 0c76fc3c2b346dc5401dc055d97d4279632b0fb3 (diff) | |
| download | glibc-6e29cb3f61ff5432c78a1c84b0d9b123a350ab36.tar.gz glibc-6e29cb3f61ff5432c78a1c84b0d9b123a350ab36.tar.xz glibc-6e29cb3f61ff5432c78a1c84b0d9b123a350ab36.zip | |
Linux: Use rseq in sched_getcpu if available
When available, use the cpu_id field from __rseq_abi on Linux to implement sched_getcpu(). Fall-back on the vgetcpu vDSO if unavailable. Benchmarks: x86-64: Intel E5-2630 v3@2.40GHz, 16-core, hyperthreading glibc sched_getcpu(): 13.7 ns (baseline) glibc sched_getcpu() using rseq: 2.5 ns (speedup: 5.5x) inline load cpuid from __rseq_abi TLS: 0.8 ns (speedup: 17.1x)
| -rw-r--r-- | sysdeps/unix/sysv/linux/sched_getcpu.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c index c019cfb3cf..c0f992e056 100644 --- a/sysdeps/unix/sysv/linux/sched_getcpu.c +++ b/sysdeps/unix/sysv/linux/sched_getcpu.c @@ -18,10 +18,12 @@ #include <errno.h> #include <sched.h> #include <sysdep.h> +#include <atomic.h> #include <sysdep-vdso.h> +#include <sys/rseq.h> -int -sched_getcpu (void) +static int +vsyscall_sched_getcpu (void) { unsigned int cpu; int r = -1; @@ -32,3 +34,19 @@ sched_getcpu (void) #endif return r == -1 ? r : cpu; } + +#ifdef RSEQ_SIG +int +sched_getcpu (void) +{ + int cpu_id = atomic_load_relaxed (&__rseq_abi.cpu_id); + + return cpu_id >= 0 ? cpu_id : vsyscall_sched_getcpu (); +} +#else /* RSEQ_SIG */ +int +sched_getcpu (void) +{ + return vsyscall_sched_getcpu (); +} +#endif /* RSEQ_SIG */ |