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| author | Tzachi Zidenberg <tsahee@amazon.com> | 2020-07-06 13:43:30 +0300 |
|---|---|---|
| committer | Tzachi Zidenberg <tsahee@amazon.com> | 2020-07-23 15:07:13 +0300 |
| commit | c76b45a5242f50d00c16f0bbf1dbecd4e359e02c (patch) | |
| tree | 262571433ede080aa64d6c9d57dbc551d080549d /include | |
| parent | 5f2628d1eea21d9732f582b77782b072e5e04014 (diff) | |
| download | mariadb-git-c76b45a5242f50d00c16f0bbf1dbecd4e359e02c.tar.gz | |
MDEV-23249: Support aarch64 architecture timer
aarch64 timer is available to userspace via arch register.
clang's __builtin_readcyclecounter is wrong for aarch64 (reads the PMU
cycle counter instead of the archi-timer register), so we don't use it.
my_rdtsc unit-test on AWS m6g shows:
frequency: 121830845
resolution: 1
overhead: 1
This counter is not strictly increasing, but it is non-decreasing.
Diffstat (limited to 'include')
| -rw-r--r-- | include/my_rdtsc.h | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/include/my_rdtsc.h b/include/my_rdtsc.h index a2e5afcb79f..33d722764d4 100644 --- a/include/my_rdtsc.h +++ b/include/my_rdtsc.h @@ -77,7 +77,7 @@ C_MODE_START /** A cycle timer. - On clang, we use __builtin_readcyclecounter(). + On clang we use __builtin_readcyclecounter(), except for AARCH64. On other compilers: On IA-32 and AMD64, we use the RDTSC instruction. @@ -88,6 +88,9 @@ C_MODE_START On IBM S/390 System z we use the STCK instruction. On ARM, we probably should use the Generic Timer, but should figure out how to ensure that it can be accessed. + On AARCH64, we use the generic timer base register. We override clang + implementation for aarch64 as it access a PMU register which is not + guarenteed to be active. Sadly, we have nothing for the Digital Alpha, MIPS, Motorola m68k, HP PA-RISC or other non-mainstream (or obsolete) processors. @@ -125,7 +128,7 @@ C_MODE_START */ static inline ulonglong my_timer_cycles(void) { -# if __has_builtin(__builtin_readcyclecounter) +# if __has_builtin(__builtin_readcyclecounter) && !defined (__aarch64__) return __builtin_readcyclecounter(); # elif defined _WIN32 || defined __i386__ || defined __x86_64__ return __rdtsc(); @@ -164,6 +167,12 @@ static inline ulonglong my_timer_cycles(void) __asm__ __volatile__ ("stck %0" : "=Q" (result) : : "cc"); return result; } +#elif defined(__GNUC__) && defined (__aarch64__) + { + ulonglong result; + __asm __volatile("mrs %0, CNTVCT_EL0" : "=&r" (result)); + return result; + } #elif defined(HAVE_SYS_TIMES_H) && defined(HAVE_GETHRTIME) /* gethrtime may appear as either cycle or nanosecond counter */ return (ulonglong) gethrtime(); @@ -221,6 +230,7 @@ C_MODE_END #define MY_TIMER_ROUTINE_MACH_ABSOLUTE_TIME 25 #define MY_TIMER_ROUTINE_GETSYSTEMTIMEASFILETIME 26 #define MY_TIMER_ROUTINE_ASM_S390 28 +#define MY_TIMER_ROUTINE_AARCH64 29 #endif |