From d07319f790eb38c867bd04a23de674e2393825ff Mon Sep 17 00:00:00 2001 From: Rickard Green Date: Sun, 22 Mar 2015 20:20:28 +0100 Subject: Better support for poor os monotonic sources --- erts/emulator/sys/unix/sys_time.c | 200 ++++++++++++-------------------------- 1 file changed, 60 insertions(+), 140 deletions(-) (limited to 'erts/emulator/sys/unix/sys_time.c') diff --git a/erts/emulator/sys/unix/sys_time.c b/erts/emulator/sys/unix/sys_time.c index 9fdb1930b7..9db727b111 100644 --- a/erts/emulator/sys/unix/sys_time.c +++ b/erts/emulator/sys/unix/sys_time.c @@ -33,6 +33,7 @@ #include "sys.h" #include "global.h" +#include "erl_os_monotonic_time_extender.h" #ifdef NO_SYSCONF # define TICKS_PER_SEC() HZ @@ -55,36 +56,19 @@ #undef ERTS_SYS_TIME_INTERNAL_STATE_WRITE_FREQ__ #undef ERTS_SYS_TIME_INTERNAL_STATE_READ_ONLY__ +#undef ERTS_SYS_TIME_INTERNAL_STATE_READ_MOSTLY__ #if defined(OS_MONOTONIC_TIME_USING_TIMES) -#define ERTS_WRAP_SYS_TIMES 1 -#define ERTS_SYS_TIME_INTERNAL_STATE_WRITE_FREQ__ -#define ERTS_SYS_TIME_INTERNAL_STATE_READ_ONLY__ - -/* - * Not sure there is a need to use times() anymore, perhaps drop - * support for this soon... - * - * sys_times() might need to be wrapped and the values shifted (right) - * a bit to cope with faster ticks, this has to be taken care - * of dynamically to start with, a special version that uses - * the times() return value as a high resolution timer can be made - * to fully utilize the faster ticks, like on windows, but for now, we'll - * settle with this silly workaround - */ -#ifdef ERTS_WRAP_SYS_TIMES -static clock_t sys_times_wrap(void); -#define KERNEL_TICKS() (sys_times_wrap() & \ - ((1UL << ((sizeof(clock_t) * 8) - 1)) - 1)) -#define ERTS_KERNEL_TICK_TO_USEC(TCKS) (((TCKS)*(1000*1000)) \ - / internal_state.r.o.ticks_per_sec_wrap) -#else +static Uint32 +get_tick_count(void) +{ + struct tms unused; + return (Uint32) times(&unused); +} -#define KERNEL_TICKS() (sys_times(&internal_state.w.f.dummy_tms) & \ - ((1UL << ((sizeof(clock_t) * 8) - 1)) - 1)) -#define ERTS_KERNEL_TICK_TO_USEC(TCKS) (((TCKS)*(1000*1000))/SYS_CLK_TCK) -#endif +#define ERTS_SYS_TIME_INTERNAL_STATE_READ_ONLY__ +#define ERTS_SYS_TIME_INTERNAL_STATE_READ_MOSTLY__ #endif @@ -109,8 +93,15 @@ ErtsMonotonicTime clock_gettime_monotonic_verified(void); #ifdef ERTS_SYS_TIME_INTERNAL_STATE_READ_ONLY__ struct sys_time_internal_state_read_only__ { #if defined(OS_MONOTONIC_TIME_USING_TIMES) - int ticks_bsr; - int ticks_per_sec_wrap; + int times_shift; +#endif +}; +#endif + +#ifdef ERTS_SYS_TIME_INTERNAL_STATE_READ_MOSTLY__ +struct sys_time_internal_state_read_mostly__ { +#if defined(OS_MONOTONIC_TIME_USING_TIMES) + ErtsOsMonotonicTimeExtendState os_mtime_xtnd; #endif }; #endif @@ -121,15 +112,6 @@ struct sys_time_internal_state_write_freq__ { #if defined(__linux__) && defined(OS_MONOTONIC_TIME_USING_CLOCK_GETTIME) ErtsMonotonicTime last_delivered; #endif -#if defined(OS_MONOTONIC_TIME_USING_TIMES) - ErtsMonotonicTime last_tick_count; - ErtsMonotonicTime last_tick_wrap_count; - ErtsMonotonicTime last_tick_monotonic_time; - ErtsMonotonicTime last_timeofday_usec; -#ifndef ERTS_WRAP_SYS_TIMES - SysTimes dummy_tms; -#endif -#endif }; #endif @@ -144,6 +126,14 @@ static struct { * ASSUMED_CACHE_LINE_SIZE]; } r; #endif +#ifdef ERTS_SYS_TIME_INTERNAL_STATE_READ_MOSTLY__ + union { + struct sys_time_internal_state_read_mostly__ m; + char align__[(((sizeof(struct sys_time_internal_state_read_mostly__) - 1) + / ASSUMED_CACHE_LINE_SIZE) + 1) + * ASSUMED_CACHE_LINE_SIZE]; + } wr; +#endif #ifdef ERTS_SYS_TIME_INTERNAL_STATE_WRITE_FREQ__ union { struct sys_time_internal_state_write_freq__ f; @@ -193,8 +183,6 @@ sys_init_time(ErtsSysInitTimeResult *init_resp) init_resp->os_monotonic_info.func = "gethrtime"; #elif defined(OS_MONOTONIC_TIME_USING_TIMES) init_resp->os_monotonic_info.func = "times"; - init_resp->os_monotonic_info.locked_use = 1; - init_resp->os_monotonic_info.resolution = TICKS_PER_SEC(); #else # error Unknown erts_os_monotonic_time() implementation #endif @@ -247,7 +235,9 @@ sys_init_time(ErtsSysInitTimeResult *init_resp) #endif /* defined(ERTS_HAVE_OS_MONOTONIC_TIME_SUPPORT) */ +#ifdef ERTS_COMPILE_TIME_MONOTONIC_TIME_UNIT init_resp->os_monotonic_time_unit = ERTS_COMPILE_TIME_MONOTONIC_TIME_UNIT; +#endif init_resp->sys_clock_resolution = SYS_CLOCK_RESOLUTION; /* @@ -258,38 +248,40 @@ sys_init_time(ErtsSysInitTimeResult *init_resp) erl_exit(ERTS_ABORT_EXIT, "Can't get clock ticks/sec\n"); #if defined(OS_MONOTONIC_TIME_USING_TIMES) +#if ERTS_COMPILE_TIME_MONOTONIC_TIME_UNIT +# error Time unit is supposed to be determined at runtime... +#endif + { + ErtsMonotonicTime resolution = erts_sys_time_data__.r.o.ticks_per_sec; + ErtsMonotonicTime time_unit = resolution; + int shift = 0; - if (erts_sys_time_data__.r.o.ticks_per_sec >= 1000) { - /* Workaround for beta linux kernels, need to be done in runtime - to make erlang run on both 2.4 and 2.5 kernels. In the future, - the kernel ticks might as - well be used as a high res timer instead, but that's for when the - majority uses kernels with HZ == 1024 */ - internal_state.r.o.ticks_bsr = 3; - } else { - internal_state.r.o.ticks_bsr = 0; - } + while (time_unit < 1000*1000) { + time_unit <<= 1; + shift++; + } - internal_state.r.o.ticks_per_sec_wrap - = (erts_sys_time_data__.r.o.ticks_per_sec - >> internal_state.r.o.ticks_bsr); + init_resp->os_monotonic_info.resolution = resolution; + init_resp->os_monotonic_time_unit = time_unit; + init_resp->os_monotonic_info.extended = 1; + internal_state.r.o.times_shift = shift; - erts_smp_mtx_init(&internal_state.w.f.mtx, "os_monotonic_time"); - internal_state.w.f.last_tick_count = KERNEL_TICKS(); - internal_state.w.f.last_tick_wrap_count = 0; - internal_state.w.f.last_tick_monotonic_time - = ERTS_KERNEL_TICK_TO_USEC(internal_state.w.f.last_tick_count); - { - SysTimeval tv; - sys_gettimeofday(&tv); - internal_state.w.f.last_timeofday_usec = tv.tv_sec*(1000*1000); - internal_state.w.f.last_timeofday_usec += tv.tv_usec; + erts_init_os_monotonic_time_extender(&internal_state.wr.m.os_mtime_xtnd, + get_tick_count, + (1 << 29) / resolution); } - #endif /* defined(OS_MONOTONIC_TIME_USING_TIMES) */ } +void +erts_late_sys_init_time(void) +{ +#if defined(OS_MONOTONIC_TIME_USING_TIMES) + erts_late_init_os_monotonic_time_extender(&internal_state.wr.m.os_mtime_xtnd); +#endif +} + #if defined(OS_MONOTONIC_TIME_USING_CLOCK_GETTIME) static ERTS_INLINE ErtsMonotonicTime @@ -379,86 +371,14 @@ ErtsMonotonicTime erts_os_monotonic_time(void) #elif defined(OS_MONOTONIC_TIME_USING_TIMES) -static clock_t sys_times_wrap(void) -{ - SysTimes dummy; - clock_t result = (sys_times(&dummy) >> internal_state.r.o.ticks_bsr); - return result; -} - -void -erts_os_time_offset_finalize(void) -{ - erts_smp_mtx_lock(&internal_state.w.f.mtx); - internal_state.w.f.last_tick_wrap_count = 0; - erts_smp_mtx_unlock(&internal_state.w.f.mtx); -} - -#define ERTS_TIME_EXCEED_TICK_LIMIT(SYS_TIME, TCK_TIME) \ - (((Uint64) (SYS_TIME)) - (((Uint64) (TCK_TIME)) \ - - ERTS_KERNEL_TICK_TO_USEC(1)) \ - > ERTS_KERNEL_TICK_TO_USEC(2)) - -/* Returns monotonic time in micro seconds */ ErtsMonotonicTime erts_os_monotonic_time(void) { - SysTimeval tv; - ErtsMonotonicTime res; - ErtsMonotonicTime tick_count; - ErtsMonotonicTime tick_count_usec; - ErtsMonotonicTime tick_monotonic_time; - ErtsMonotonicTime timeofday_usec; - ErtsMonotonicTime timeofday_diff_usec; - - erts_smp_mtx_lock(&internal_state.w.f.mtx); - - tick_count = (ErtsMonotonicTime) KERNEL_TICKS(); - sys_gettimeofday(&tv); - - if (internal_state.w.f.last_tick_count > tick_count) { - internal_state.w.f.last_tick_wrap_count - += (((ErtsMonotonicTime) 1) << ((sizeof(clock_t) * 8) - 1)); - } - internal_state.w.f.last_tick_count = tick_count; - tick_count += internal_state.w.f.last_tick_wrap_count; - - tick_count_usec = ERTS_KERNEL_TICK_TO_USEC(tick_count); - - timeofday_usec = (ErtsMonotonicTime) tv.tv_sec*(1000*1000); - timeofday_usec += (ErtsMonotonicTime) tv.tv_usec; - timeofday_diff_usec = timeofday_usec; - timeofday_diff_usec -= internal_state.w.f.last_timeofday_usec; - internal_state.w.f.last_timeofday_usec = timeofday_usec; - - if (timeofday_diff_usec < 0) { - /* timeofday jumped backwards use tick count only... */ - tick_monotonic_time = tick_count_usec; - } - else { - /* Use time diff from of timeofday if not off by too much... */ - tick_monotonic_time = internal_state.w.f.last_tick_monotonic_time; - tick_monotonic_time += timeofday_diff_usec; - - if (ERTS_TIME_EXCEED_TICK_LIMIT(tick_monotonic_time, tick_count_usec)) { - /* - * Value off by more than one tick from tick_count, i.e. - * timofday leaped one way or the other. We use - * tick_count_usec as is instead and unfortunately - * get lousy precision. - */ - tick_monotonic_time = tick_count_usec; - } - } - - if (internal_state.w.f.last_tick_monotonic_time < tick_monotonic_time) - internal_state.w.f.last_tick_monotonic_time = tick_monotonic_time; - - res = internal_state.w.f.last_tick_monotonic_time; - - erts_smp_mtx_unlock(&internal_state.w.f.mtx); - - return res; + Uint32 ticks = get_tick_count(); + ERTS_CHK_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd, + ticks); + return ERTS_EXTEND_OS_MONOTONIC_TIME(&internal_state.wr.m.os_mtime_xtnd, + ticks) << internal_state.r.o.times_shift; } #endif /* !defined(OS_MONOTONIC_TIME_USING_TIMES) */ -- cgit v1.2.3