|
| 1 | +/* |
| 2 | + * Copyright (c) 2022 Cisco Systems, Inc. All rights reserved. |
| 3 | + * $COPYRIGHT$ |
| 4 | + * |
| 5 | + * Additional copyrights may follow |
| 6 | + * |
| 7 | + * $HEADER$ |
| 8 | + */ |
| 9 | + |
| 10 | +/** @file clock_gettime.h |
| 11 | + * |
| 12 | + * Simple, portable wrappers around clock_gettime(3) and |
| 13 | + * clock_getres(3) to always get monotonically-increasing time. |
| 14 | + * |
| 15 | + * If the underlying OS does not have clock_gettime(3), use |
| 16 | + * gettimeofday(3) instead. |
| 17 | + * |
| 18 | + * We intentionally do not use the OPAL timer framework for |
| 19 | + * high-prevision time here; see |
| 20 | + * https://github.com/open-mpi/ompi/issues/3003 for more details. |
| 21 | + * |
| 22 | + * As of Dec 2021, it turns out that CLOCK_MONOTONIC can actually go |
| 23 | + * backwards on macOS (!). CLOCK_MONOTONIC does *not* go backwards on |
| 24 | + * Linux (or anywhere else we can find), though, even in the presence |
| 25 | + * of small NTP time adjustments -- e.g., adjtime(3) simply slightly |
| 26 | + * speeds up or slows down the system clock to make it eventually get |
| 27 | + * to the desired time. On macOS, we can use CLOCK_MONOTONIC_RAW, |
| 28 | + * which never goes backwards. |
| 29 | + * |
| 30 | + * Hence, for these wrappers, use CLOCK_MONOTONIC_RAW on Darwin, and |
| 31 | + * use CLOCK_MONOTONIC everywhere else. |
| 32 | + * |
| 33 | + * See |
| 34 | + * https://github.com/open-mpi/ompi/pull/8057#discussion_r762612710 |
| 35 | + * and |
| 36 | + * https://github.com/open-mpi/ompi/pull/8057#discussion_r762618783 |
| 37 | + * for more details. |
| 38 | + */ |
| 39 | + |
| 40 | +#ifndef OPAL_UTIL_CLOCK_GETTIME_H_ |
| 41 | +#define OPAL_UTIL_CLOCK_GETTIME_H_ |
| 42 | + |
| 43 | +#include "opal_config.h" |
| 44 | + |
| 45 | +#if HAVE_TIME_H |
| 46 | +#include <time.h> |
| 47 | +#endif |
| 48 | +#if HAVE_SYS_TIME_H |
| 49 | +#include <sys/time.h> |
| 50 | +#endif |
| 51 | + |
| 52 | +#if OPAL_HAVE_CLOCK_GETTIME |
| 53 | +#if defined(__darwin__) |
| 54 | +#define OPAL_CLOCK_TYPE CLOCK_MONOTONIC_RAW |
| 55 | +#else |
| 56 | +#define OPAL_CLOCK_TYPE CLOCK_MONOTONIC |
| 57 | +#endif |
| 58 | +#endif // OPAL_HAVE_CLOCK_GETTIME |
| 59 | + |
| 60 | +#if !defined(HAVE_STRUCT_TIMESPEC_TV_NSEC) |
| 61 | +// Make sure that we have struct timespec; if not, define it. |
| 62 | +struct timespec { |
| 63 | + time_t tv_sec; |
| 64 | + long tv_nsec; |
| 65 | +}; |
| 66 | +#endif |
| 67 | + |
| 68 | +/** |
| 69 | + * Simple, portable wrapper around clock_gettime(3) for high-precision time. |
| 70 | + * |
| 71 | + * If the underlying system does not have clock_gettime(3), use |
| 72 | + * gettimeofday(3) instead. |
| 73 | + * |
| 74 | + * @param spec (OUT) Struct to return the time |
| 75 | + * @return Return value from underlying clock_gettime() |
| 76 | + */ |
| 77 | +static inline int opal_clock_gettime(struct timespec *spec) |
| 78 | +{ |
| 79 | +#if OPAL_HAVE_CLOCK_GETTIME |
| 80 | + return clock_gettime(OPAL_CLOCK_TYPE, spec); |
| 81 | +#else |
| 82 | + // If we do not have clock_gettime(), fall back to gettimeofday() |
| 83 | + struct timeval tv; |
| 84 | + int ret = gettimeofday(&tv, NULL); |
| 85 | + |
| 86 | + spec->tv_sec = tv.tv_sec; |
| 87 | + // Elevate the micrseconds to nanoseconds |
| 88 | + spec->tv_nsec = tv.tv_usec * 1000; |
| 89 | + |
| 90 | + return ret; |
| 91 | +#endif |
| 92 | +} |
| 93 | + |
| 94 | +/** |
| 95 | + * Simple, portable wrapper around clock_getres(3) for high-precision time. |
| 96 | + * |
| 97 | + * If the underlying system does not have clock_gettime(3), return usec |
| 98 | + * precison (because opal_clock_gettime() will be using gettimeofday(3)). |
| 99 | + * |
| 100 | + * @param spec (OUT) Struct to return the resolution |
| 101 | + * @return Return value from underlying clock_getres() |
| 102 | + */ |
| 103 | +static inline int opal_clock_getres(struct timespec *spec) |
| 104 | +{ |
| 105 | +#if OPAL_HAVE_CLOCK_GETTIME |
| 106 | + return clock_getres(OPAL_CLOCK_TYPE, spec); |
| 107 | +#else |
| 108 | + // If we don't have clock_gettime(), just return usec precision. |
| 109 | + spec->tv_sec = 0; |
| 110 | + spec->tv_nsec = 1000; |
| 111 | + |
| 112 | + return 0; |
| 113 | +#endif |
| 114 | +} |
| 115 | + |
| 116 | +#endif // OPAL_UTIL_CLOCK_GETTIME_H_ |
0 commit comments