diff options
Diffstat (limited to 'src/core/lib/iomgr/combiner.c')
-rw-r--r-- | src/core/lib/iomgr/combiner.c | 372 |
1 files changed, 208 insertions, 164 deletions
diff --git a/src/core/lib/iomgr/combiner.c b/src/core/lib/iomgr/combiner.c index 831bdb4aff..60ee14eb23 100644 --- a/src/core/lib/iomgr/combiner.c +++ b/src/core/lib/iomgr/combiner.c @@ -50,25 +50,57 @@ int grpc_combiner_trace = 0; } \ } while (0) +#define STATE_UNORPHANED 1 +#define STATE_ELEM_COUNT_LOW_BIT 2 + struct grpc_combiner { + grpc_combiner *next_combiner_on_this_exec_ctx; grpc_workqueue *optional_workqueue; gpr_mpscq queue; // state is: - // lower bit - zero if orphaned - // other bits - number of items queued on the lock + // lower bit - zero if orphaned (STATE_UNORPHANED) + // other bits - number of items queued on the lock (STATE_ELEM_COUNT_LOW_BIT) gpr_atm state; - bool take_async_break_before_final_list; + // number of elements in the list that are covered by a poller: if >0, we can + // offload safely + gpr_atm elements_covered_by_poller; + bool time_to_execute_final_list; + bool final_list_covered_by_poller; grpc_closure_list final_list; - grpc_closure continue_finishing; + grpc_closure offload; }; +static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error); + +typedef struct { + grpc_error *error; + bool covered_by_poller; +} error_data; + +static uintptr_t pack_error_data(error_data d) { + return ((uintptr_t)d.error) | (d.covered_by_poller ? 1 : 0); +} + +static error_data unpack_error_data(uintptr_t p) { + return (error_data){(grpc_error *)(p & ~(uintptr_t)1), p & 1}; +} + +static bool is_covered_by_poller(grpc_combiner *lock) { + return lock->final_list_covered_by_poller || + gpr_atm_acq_load(&lock->elements_covered_by_poller) > 0; +} + grpc_combiner *grpc_combiner_create(grpc_workqueue *optional_workqueue) { grpc_combiner *lock = gpr_malloc(sizeof(*lock)); + lock->next_combiner_on_this_exec_ctx = NULL; + lock->time_to_execute_final_list = false; lock->optional_workqueue = optional_workqueue; - gpr_atm_no_barrier_store(&lock->state, 1); + lock->final_list_covered_by_poller = false; + gpr_atm_no_barrier_store(&lock->state, STATE_UNORPHANED); + gpr_atm_no_barrier_store(&lock->elements_covered_by_poller, 0); gpr_mpscq_init(&lock->queue); - lock->take_async_break_before_final_list = false; grpc_closure_list_init(&lock->final_list); + grpc_closure_init(&lock->offload, offload, lock); GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p create", lock)); return lock; } @@ -82,7 +114,7 @@ static void really_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { } void grpc_combiner_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { - gpr_atm old_state = gpr_atm_full_fetch_add(&lock->state, -1); + gpr_atm old_state = gpr_atm_full_fetch_add(&lock->state, -STATE_UNORPHANED); GRPC_COMBINER_TRACE(gpr_log( GPR_DEBUG, "C:%p really_destroy old_state=%" PRIdPTR, lock, old_state)); if (old_state == 1) { @@ -90,170 +122,186 @@ void grpc_combiner_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { } } -static bool maybe_finish_one(grpc_exec_ctx *exec_ctx, grpc_combiner *lock); -static void finish(grpc_exec_ctx *exec_ctx, grpc_combiner *lock); +static void push_last_on_exec_ctx(grpc_exec_ctx *exec_ctx, + grpc_combiner *lock) { + lock->next_combiner_on_this_exec_ctx = NULL; + if (exec_ctx->active_combiner == NULL) { + exec_ctx->active_combiner = exec_ctx->last_combiner = lock; + } else { + exec_ctx->last_combiner->next_combiner_on_this_exec_ctx = lock; + exec_ctx->last_combiner = lock; + } +} -static void continue_finishing_mainline(grpc_exec_ctx *exec_ctx, void *arg, - grpc_error *error) { - GPR_TIMER_BEGIN("combiner.continue_executing_mainline", 0); - grpc_combiner *lock = arg; - GRPC_COMBINER_TRACE( - gpr_log(GPR_DEBUG, "C:%p continue_finishing_mainline", lock)); - GPR_ASSERT(exec_ctx->active_combiner == NULL); +static void push_first_on_exec_ctx(grpc_exec_ctx *exec_ctx, + grpc_combiner *lock) { + lock->next_combiner_on_this_exec_ctx = exec_ctx->active_combiner; exec_ctx->active_combiner = lock; - if (maybe_finish_one(exec_ctx, lock)) finish(exec_ctx, lock); - GPR_ASSERT(exec_ctx->active_combiner == lock); - exec_ctx->active_combiner = NULL; - GPR_TIMER_END("combiner.continue_executing_mainline", 0); + if (lock->next_combiner_on_this_exec_ctx == NULL) { + exec_ctx->last_combiner = lock; + } } -static void execute_final(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { - GPR_TIMER_BEGIN("combiner.execute_final", 0); - grpc_closure *c = lock->final_list.head; - GPR_ASSERT(c != NULL); - grpc_closure_list_init(&lock->final_list); - lock->take_async_break_before_final_list = false; - int loops = 0; - while (c != NULL) { - GRPC_COMBINER_TRACE( - gpr_log(GPR_DEBUG, "C:%p execute_final[%d] c=%p", lock, loops, c)); - grpc_closure *next = c->next_data.next; - grpc_error *error = c->error; - c->cb(exec_ctx, c->cb_arg, error); - GRPC_ERROR_UNREF(error); - c = next; - loops++; +void grpc_combiner_execute(grpc_exec_ctx *exec_ctx, grpc_combiner *lock, + grpc_closure *cl, grpc_error *error, + bool covered_by_poller) { + GPR_TIMER_BEGIN("combiner.execute", 0); + gpr_atm last = gpr_atm_full_fetch_add(&lock->state, STATE_ELEM_COUNT_LOW_BIT); + GRPC_COMBINER_TRACE(gpr_log( + GPR_DEBUG, "C:%p grpc_combiner_execute c=%p cov=%d last=%" PRIdPTR, lock, + cl, covered_by_poller, last)); + GPR_ASSERT(last & STATE_UNORPHANED); // ensure lock has not been destroyed + cl->error_data.scratch = + pack_error_data((error_data){error, covered_by_poller}); + if (covered_by_poller) { + gpr_atm_no_barrier_fetch_add(&lock->elements_covered_by_poller, 1); + } + gpr_mpscq_push(&lock->queue, &cl->next_data.atm_next); + if (last == 1) { + // first element on this list: add it to the list of combiner locks + // executing within this exec_ctx + push_last_on_exec_ctx(exec_ctx, lock); } - GPR_TIMER_END("combiner.execute_final", 0); + GPR_TIMER_END("combiner.execute", 0); } -static void continue_executing_final(grpc_exec_ctx *exec_ctx, void *arg, - grpc_error *error) { - GPR_TIMER_BEGIN("combiner.continue_executing_final", 0); - grpc_combiner *lock = arg; - GRPC_COMBINER_TRACE( - gpr_log(GPR_DEBUG, "C:%p continue_executing_final", lock)); - GPR_ASSERT(exec_ctx->active_combiner == NULL); - exec_ctx->active_combiner = lock; - // quick peek to see if new things have turned up on the queue: if so, go back - // to executing them before the final list - if ((gpr_atm_acq_load(&lock->state) >> 1) > 1) { - if (maybe_finish_one(exec_ctx, lock)) finish(exec_ctx, lock); - } else { - execute_final(exec_ctx, lock); - finish(exec_ctx, lock); +static void move_next(grpc_exec_ctx *exec_ctx) { + exec_ctx->active_combiner = + exec_ctx->active_combiner->next_combiner_on_this_exec_ctx; + if (exec_ctx->active_combiner == NULL) { + exec_ctx->last_combiner = NULL; } - GPR_ASSERT(exec_ctx->active_combiner == lock); - exec_ctx->active_combiner = NULL; - GPR_TIMER_END("combiner.continue_executing_final", 0); } -static bool start_execute_final(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { - GPR_TIMER_BEGIN("combiner.start_execute_final", 0); - GPR_ASSERT(exec_ctx->active_combiner == lock); - GRPC_COMBINER_TRACE( - gpr_log(GPR_DEBUG, - "C:%p start_execute_final take_async_break_before_final_list=%d", - lock, lock->take_async_break_before_final_list)); - if (lock->take_async_break_before_final_list) { - grpc_closure_init(&lock->continue_finishing, continue_executing_final, - lock); - grpc_exec_ctx_sched(exec_ctx, &lock->continue_finishing, GRPC_ERROR_NONE, - GRPC_WORKQUEUE_REF(lock->optional_workqueue, "sched")); - GPR_TIMER_END("combiner.start_execute_final", 0); +static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) { + grpc_combiner *lock = arg; + push_last_on_exec_ctx(exec_ctx, lock); +} + +static void queue_offload(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { + move_next(exec_ctx); + GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p queue_offload --> %p", lock, + lock->optional_workqueue)); + grpc_workqueue_enqueue(exec_ctx, lock->optional_workqueue, &lock->offload, + GRPC_ERROR_NONE); +} + +bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx) { + GPR_TIMER_BEGIN("combiner.continue_exec_ctx", 0); + grpc_combiner *lock = exec_ctx->active_combiner; + if (lock == NULL) { + GPR_TIMER_END("combiner.continue_exec_ctx", 0); return false; - } else { - execute_final(exec_ctx, lock); - GPR_TIMER_END("combiner.start_execute_final", 0); - return true; } -} -static bool maybe_finish_one(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { - GPR_TIMER_BEGIN("combiner.maybe_finish_one", 0); - gpr_mpscq_node *n = gpr_mpscq_pop(&lock->queue); GRPC_COMBINER_TRACE( - gpr_log(GPR_DEBUG, "C:%p maybe_finish_one n=%p", lock, n)); - GPR_ASSERT(exec_ctx->active_combiner == lock); - if (n == NULL) { - // Queue is in an transiently inconsistent state: a new item is being queued - // but is not visible to this thread yet. - // Use this as a cue that we should go off and do something else for a while - // (and come back later) - grpc_closure_init(&lock->continue_finishing, continue_finishing_mainline, - lock); - grpc_exec_ctx_sched(exec_ctx, &lock->continue_finishing, GRPC_ERROR_NONE, - GRPC_WORKQUEUE_REF(lock->optional_workqueue, "sched")); - GPR_TIMER_END("combiner.maybe_finish_one", 0); - return false; + gpr_log(GPR_DEBUG, + "C:%p grpc_combiner_continue_exec_ctx workqueue=%p " + "is_covered_by_poller=%d exec_ctx_ready_to_finish=%d " + "time_to_execute_final_list=%d", + lock, lock->optional_workqueue, is_covered_by_poller(lock), + grpc_exec_ctx_ready_to_finish(exec_ctx), + lock->time_to_execute_final_list)); + + if (lock->optional_workqueue != NULL && is_covered_by_poller(lock) && + grpc_exec_ctx_ready_to_finish(exec_ctx)) { + GPR_TIMER_MARK("offload_from_finished_exec_ctx", 0); + // this execution context wants to move on, and we have a workqueue (and + // so can help the execution context out): schedule remaining work to be + // picked up on the workqueue + queue_offload(exec_ctx, lock); + GPR_TIMER_END("combiner.continue_exec_ctx", 0); + return true; } - grpc_closure *cl = (grpc_closure *)n; - grpc_error *error = cl->error; - cl->cb(exec_ctx, cl->cb_arg, error); - GRPC_ERROR_UNREF(error); - GPR_TIMER_END("combiner.maybe_finish_one", 0); - return true; -} -static void finish(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) { - bool (*executor)(grpc_exec_ctx * exec_ctx, grpc_combiner * lock); - GPR_TIMER_BEGIN("combiner.finish", 0); - int loops = 0; - do { - executor = maybe_finish_one; - gpr_atm old_state = gpr_atm_full_fetch_add(&lock->state, -2); - GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, - "C:%p finish[%d] old_state=%" PRIdPTR, lock, - loops, old_state)); - switch (old_state) { - default: - // we have multiple queued work items: just continue executing them - break; - case 5: // we're down to one queued item: if it's the final list we - case 4: // should do that - if (!grpc_closure_list_empty(lock->final_list)) { - executor = start_execute_final; - } - break; - case 3: // had one count, one unorphaned --> unlocked unorphaned - GPR_TIMER_END("combiner.finish", 0); - return; - case 2: // and one count, one orphaned --> unlocked and orphaned - really_destroy(exec_ctx, lock); - GPR_TIMER_END("combiner.finish", 0); - return; - case 1: - case 0: - // these values are illegal - representing an already unlocked or - // deleted lock - GPR_UNREACHABLE_CODE(return ); + if (!lock->time_to_execute_final_list || + // peek to see if something new has shown up, and execute that with + // priority + (gpr_atm_acq_load(&lock->state) >> 1) > 1) { + gpr_mpscq_node *n = gpr_mpscq_pop(&lock->queue); + GRPC_COMBINER_TRACE( + gpr_log(GPR_DEBUG, "C:%p maybe_finish_one n=%p", lock, n)); + if (n == NULL) { + // queue is in an inconsistent state: use this as a cue that we should + // go off and do something else for a while (and come back later) + GPR_TIMER_MARK("delay_busy", 0); + if (lock->optional_workqueue != NULL && is_covered_by_poller(lock)) { + queue_offload(exec_ctx, lock); + } + GPR_TIMER_END("combiner.continue_exec_ctx", 0); + return true; } - loops++; - } while (executor(exec_ctx, lock)); - GPR_TIMER_END("combiner.finish", 0); -} + GPR_TIMER_BEGIN("combiner.exec1", 0); + grpc_closure *cl = (grpc_closure *)n; + error_data err = unpack_error_data(cl->error_data.scratch); + cl->cb(exec_ctx, cl->cb_arg, err.error); + if (err.covered_by_poller) { + gpr_atm_no_barrier_fetch_add(&lock->elements_covered_by_poller, -1); + } + GRPC_ERROR_UNREF(err.error); + GPR_TIMER_END("combiner.exec1", 0); + } else { + grpc_closure *c = lock->final_list.head; + GPR_ASSERT(c != NULL); + grpc_closure_list_init(&lock->final_list); + lock->final_list_covered_by_poller = false; + int loops = 0; + while (c != NULL) { + GPR_TIMER_BEGIN("combiner.exec_1final", 0); + GRPC_COMBINER_TRACE( + gpr_log(GPR_DEBUG, "C:%p execute_final[%d] c=%p", lock, loops, c)); + grpc_closure *next = c->next_data.next; + grpc_error *error = c->error_data.error; + c->cb(exec_ctx, c->cb_arg, error); + GRPC_ERROR_UNREF(error); + c = next; + GPR_TIMER_END("combiner.exec_1final", 0); + } + } -void grpc_combiner_execute(grpc_exec_ctx *exec_ctx, grpc_combiner *lock, - grpc_closure *cl, grpc_error *error) { + GPR_TIMER_MARK("unref", 0); + move_next(exec_ctx); + lock->time_to_execute_final_list = false; + gpr_atm old_state = + gpr_atm_full_fetch_add(&lock->state, -STATE_ELEM_COUNT_LOW_BIT); GRPC_COMBINER_TRACE( - gpr_log(GPR_DEBUG, "C:%p grpc_combiner_execute c=%p", lock, cl)); - GPR_TIMER_BEGIN("combiner.execute", 0); - gpr_atm last = gpr_atm_full_fetch_add(&lock->state, 2); - GPR_ASSERT(last & 1); // ensure lock has not been destroyed - if (last == 1) { - exec_ctx->active_combiner = lock; - GPR_TIMER_BEGIN("combiner.execute_first_cb", 0); - cl->cb(exec_ctx, cl->cb_arg, error); - GPR_TIMER_END("combiner.execute_first_cb", 0); - GRPC_ERROR_UNREF(error); - finish(exec_ctx, lock); - GPR_ASSERT(exec_ctx->active_combiner == lock); - exec_ctx->active_combiner = NULL; - } else { - cl->error = error; - gpr_mpscq_push(&lock->queue, &cl->next_data.atm_next); + gpr_log(GPR_DEBUG, "C:%p finish old_state=%" PRIdPTR, lock, old_state)); +// Define a macro to ease readability of the following switch statement. +#define OLD_STATE_WAS(orphaned, elem_count) \ + (((orphaned) ? 0 : STATE_UNORPHANED) | \ + ((elem_count)*STATE_ELEM_COUNT_LOW_BIT)) + // Depending on what the previous state was, we need to perform different + // actions. + switch (old_state) { + default: + // we have multiple queued work items: just continue executing them + break; + case OLD_STATE_WAS(false, 2): + case OLD_STATE_WAS(true, 2): + // we're down to one queued item: if it's the final list we should do that + if (!grpc_closure_list_empty(lock->final_list)) { + lock->time_to_execute_final_list = true; + } + break; + case OLD_STATE_WAS(false, 1): + // had one count, one unorphaned --> unlocked unorphaned + GPR_TIMER_END("combiner.continue_exec_ctx", 0); + return true; + case OLD_STATE_WAS(true, 1): + // and one count, one orphaned --> unlocked and orphaned + really_destroy(exec_ctx, lock); + GPR_TIMER_END("combiner.continue_exec_ctx", 0); + return true; + case OLD_STATE_WAS(false, 0): + case OLD_STATE_WAS(true, 0): + // these values are illegal - representing an already unlocked or + // deleted lock + GPR_TIMER_END("combiner.continue_exec_ctx", 0); + GPR_UNREACHABLE_CODE(return true); } - GPR_TIMER_END("combiner.execute", 0); + push_first_on_exec_ctx(exec_ctx, lock); + GPR_TIMER_END("combiner.continue_exec_ctx", 0); + return true; } static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure, @@ -264,30 +312,26 @@ static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure, void grpc_combiner_execute_finally(grpc_exec_ctx *exec_ctx, grpc_combiner *lock, grpc_closure *closure, grpc_error *error, - bool force_async_break) { + bool covered_by_poller) { GRPC_COMBINER_TRACE(gpr_log( - GPR_DEBUG, - "C:%p grpc_combiner_execute_finally c=%p force_async_break=%d; ac=%p", - lock, closure, force_async_break, exec_ctx->active_combiner)); + GPR_DEBUG, "C:%p grpc_combiner_execute_finally c=%p; ac=%p; cov=%d", lock, + closure, exec_ctx->active_combiner, covered_by_poller)); GPR_TIMER_BEGIN("combiner.execute_finally", 0); if (exec_ctx->active_combiner != lock) { GPR_TIMER_MARK("slowpath", 0); grpc_combiner_execute(exec_ctx, lock, - grpc_closure_create(enqueue_finally, closure), error); + grpc_closure_create(enqueue_finally, closure), error, + false); GPR_TIMER_END("combiner.execute_finally", 0); return; } - if (force_async_break) { - lock->take_async_break_before_final_list = true; - } if (grpc_closure_list_empty(lock->final_list)) { - gpr_atm_full_fetch_add(&lock->state, 2); + gpr_atm_full_fetch_add(&lock->state, STATE_ELEM_COUNT_LOW_BIT); + } + if (covered_by_poller) { + lock->final_list_covered_by_poller = true; } grpc_closure_list_append(&lock->final_list, closure, error); GPR_TIMER_END("combiner.execute_finally", 0); } - -void grpc_combiner_force_async_finally(grpc_combiner *lock) { - lock->take_async_break_before_final_list = true; -} |