From adec898daf9223484f5900f7d247cbaff6f4a11b Mon Sep 17 00:00:00 2001 From: Lukas Larsson Date: Mon, 7 Jan 2019 14:38:48 +0100 Subject: erts: Use reduction based polling for starved poll-set When the schedulers never go to sleep (and thus never polls) it may be that the fds in schedulers poll-sets are never polled. Before this commit, this was solved by starting a timer when an overload was detected. This had issues as overloads were not always detected in time. So this commit reverts to the pre OTP-21 behaviour so keep a global counter makes that the poll is called when it should. --- erts/emulator/beam/erl_process.c | 86 +++++++++++++++++----------------------- erts/emulator/beam/erl_process.h | 2 - 2 files changed, 37 insertions(+), 51 deletions(-) diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c index 2427d87f66..73c99f7fb0 100644 --- a/erts/emulator/beam/erl_process.c +++ b/erts/emulator/beam/erl_process.c @@ -344,6 +344,7 @@ erts_sched_stat_t erts_sched_stat; static erts_tsd_key_t ERTS_WRITE_UNLIKELY(sched_data_key); #if ERTS_POLL_USE_SCHEDULER_POLLING +static erts_atomic32_t function_calls; static erts_atomic32_t doing_sys_schedule; #endif static erts_atomic32_t no_empty_run_queues; @@ -3251,6 +3252,7 @@ poll_thread(void *arg) static ERTS_INLINE void clear_sys_scheduling(void) { + erts_atomic32_set_relb(&function_calls, 0); erts_atomic32_set_mb(&doing_sys_schedule, 0); } @@ -3273,28 +3275,6 @@ prepare_for_sys_schedule(void) return 0; } -static void -check_io_timer(void *null) -{ - ErtsSchedulerData *esdp = erts_get_scheduler_data(); - if (prepare_for_sys_schedule()) { - erts_check_io(esdp->ssi->psi, ERTS_POLL_NO_TIMEOUT); - clear_sys_scheduling(); - } - - /* The timer is cleared if this schedulers run-queue became empty - or if the CHECKIO flag was cleared. The CHECKIO flags is cleared - when a check_balance assigns another scheduler to be the poller in - the overload scenario. */ - if ((ERTS_RUNQ_FLGS_GET_NOB(esdp->run_queue) & (ERTS_RUNQ_FLG_OUT_OF_WORK|ERTS_RUNQ_FLG_CHECKIO)) - == ERTS_RUNQ_FLG_CHECKIO) { - erts_start_timer_callback(ERTS_POLL_SCHEDULER_POLLING_TIMEOUT, - check_io_timer, NULL); - } else { - ERTS_RUNQ_FLGS_UNSET(esdp->run_queue, ERTS_RUNQ_FLG_CHECKIO); - } -} - #else #define clear_sys_scheduling() #define prepare_for_sys_schedule() 0 @@ -3406,6 +3386,7 @@ scheduler_wait(int *fcalls, ErtsSchedulerData *esdp, ErtsRunQueue *rq) current_time = erts_get_monotonic_time(esdp); } } + *fcalls = 0; clear_sys_scheduling(); } else { if (!ERTS_SCHEDULER_IS_DIRTY(esdp)) { @@ -4661,15 +4642,6 @@ check_balance(ErtsRunQueue *c_rq) if (blnc_no_rqs == 1) { c_rq->check_balance_reds = INT_MAX; erts_atomic32_set_nob(&balance_info.checking_balance, 0); -#if ERTS_POLL_USE_SCHEDULER_POLLING - c_rq->check_balance_reds = ERTS_RUNQ_CALL_CHECK_BALANCE_REDS; - if ((ERTS_RUNQ_FLGS_GET_NOB(c_rq) & (ERTS_RUNQ_FLG_OUT_OF_WORK|ERTS_RUNQ_FLG_CHECKIO)) - == 0) { - ERTS_RUNQ_FLGS_SET(c_rq, ERTS_RUNQ_FLG_CHECKIO); - erts_start_timer_callback(ERTS_POLL_SCHEDULER_POLLING_TIMEOUT, check_io_timer, NULL); - } - ERTS_RUNQ_FLGS_UNSET(c_rq, ERTS_RUNQ_FLGS_MIGRATION_INFO); -#endif return; } @@ -5189,19 +5161,6 @@ erts_fprintf(stderr, "--------------------------------\n"); /* Publish new migration paths... */ erts_atomic_set_wb(&erts_migration_paths, (erts_aint_t) new_mpaths); -#if ERTS_POLL_USE_SCHEDULER_POLLING - if (full_scheds == current_active) { - ERTS_ASSERT(full_scheds <= current_active); - /* All active schedulers ran for full, we need to do active polling, - so we setup a timer that does active polling */ - if (!(ERTS_RUNQ_FLGS_GET_NOB(c_rq) & ERTS_RUNQ_FLG_CHECKIO)) { - /* Active polling is not running, start it */ - erts_start_timer_callback(ERTS_POLL_SCHEDULER_POLLING_TIMEOUT, check_io_timer, NULL); - } - run_queue_info[c_rq->ix].flags |= ERTS_RUNQ_FLG_CHECKIO; - } -#endif - /* Reset balance statistics in all online queues */ for (qix = 0; qix < blnc_no_rqs; qix++) { Uint32 flags = run_queue_info[qix].flags; @@ -5211,8 +5170,6 @@ erts_fprintf(stderr, "--------------------------------\n"); ASSERT(!(flags & ERTS_RUNQ_FLG_OUT_OF_WORK)); if (rq->waiting) flags |= ERTS_RUNQ_FLG_OUT_OF_WORK; - if (rq != c_rq) - flags &= ~ERTS_RUNQ_FLG_CHECKIO; rq->full_reds_history_sum = run_queue_info[qix].full_reds_history_sum; @@ -5222,7 +5179,7 @@ erts_fprintf(stderr, "--------------------------------\n"); ERTS_DBG_CHK_FULL_REDS_HISTORY(rq); rq->out_of_work_count = 0; - (void) ERTS_RUNQ_FLGS_READ_BSET(rq, ERTS_RUNQ_FLGS_MIGRATION_INFO|ERTS_RUNQ_FLG_CHECKIO, flags); + (void) ERTS_RUNQ_FLGS_READ_BSET(rq, ERTS_RUNQ_FLGS_MIGRATION_INFO, flags); rq->max_len = erts_atomic32_read_dirty(&rq->len); for (pix = 0; pix < ERTS_NO_PRIO_LEVELS; pix++) { ErtsRunQueueInfo *rqi; @@ -5873,6 +5830,7 @@ erts_init_scheduling(int no_schedulers, int no_schedulers_online, int no_poll_th erts_alloc_permanent_cache_aligned(ERTS_ALC_T_RUNQS, size_runqs); #if ERTS_POLL_USE_SCHEDULER_POLLING erts_atomic32_init_nob(&doing_sys_schedule, 0); + erts_atomic32_init_nob(&function_calls, 0); #endif erts_atomic32_init_nob(&no_empty_run_queues, 0); @@ -9217,7 +9175,7 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls) Process *proxy_p = NULL; ErtsRunQueue *rq; int context_reds; - int fcalls; + int fcalls = 0; int actual_reds; int reds; Uint32 flags; @@ -9291,6 +9249,10 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls) reds = ERTS_PROC_MIN_CONTEXT_SWITCH_REDS_COST; esdp->virtual_reds = 0; +#if ERTS_POLL_USE_SCHEDULER_POLLING + fcalls = (int) erts_atomic32_add_read_acqb(&function_calls, reds); +#endif + ASSERT(esdp && esdp == erts_get_scheduler_data()); rq = erts_get_runq_current(esdp); @@ -9507,7 +9469,33 @@ Process *erts_schedule(ErtsSchedulerData *esdp, Process *p, int calls) non_empty_runq(rq); goto check_activities_to_run; - } + } else if (is_normal_sched && + fcalls > (2 * context_reds) && + prepare_for_sys_schedule()) { + ErtsMonotonicTime current_time; + /* + * Schedule system-level activities. + */ + + ERTS_MSACC_PUSH_STATE_CACHED_M(); + + erts_runq_unlock(rq); + + ERTS_MSACC_SET_STATE_CACHED_M(ERTS_MSACC_STATE_CHECK_IO); + LTTNG2(scheduler_poll, esdp->no, 1); + + erts_check_io(esdp->ssi->psi, ERTS_POLL_NO_TIMEOUT); + ERTS_MSACC_POP_STATE_M(); + + current_time = erts_get_monotonic_time(esdp); + if (current_time >= erts_next_timeout_time(esdp->next_tmo_ref)) + erts_bump_timers(esdp->timer_wheel, current_time); + + erts_runq_lock(rq); + fcalls = 0; + clear_sys_scheduling(); + goto continue_check_activities_to_run; + } if (flags & ERTS_RUNQ_FLG_MISC_OP) exec_misc_ops(rq); diff --git a/erts/emulator/beam/erl_process.h b/erts/emulator/beam/erl_process.h index a1b029adbe..9a22858f2a 100644 --- a/erts/emulator/beam/erl_process.h +++ b/erts/emulator/beam/erl_process.h @@ -173,8 +173,6 @@ extern int erts_dio_sched_thread_suggested_stack_size; (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 9)) #define ERTS_RUNQ_FLG_HALTING \ (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 10)) -#define ERTS_RUNQ_FLG_CHECKIO \ - (((Uint32) 1) << (ERTS_RUNQ_FLG_BASE2 + 11)) #define ERTS_RUNQ_FLG_MAX (ERTS_RUNQ_FLG_BASE2 + 12) -- cgit v1.2.3