diff options
Diffstat (limited to 'src/backend')
| -rw-r--r-- | src/backend/executor/tqueue.c | 2 | ||||
| -rw-r--r-- | src/backend/libpq/pqmq.c | 7 | ||||
| -rw-r--r-- | src/backend/storage/ipc/shm_mq.c | 62 |
3 files changed, 59 insertions, 12 deletions
diff --git a/src/backend/executor/tqueue.c b/src/backend/executor/tqueue.c index 7af9fbe9848..eb0cbd7b217 100644 --- a/src/backend/executor/tqueue.c +++ b/src/backend/executor/tqueue.c @@ -60,7 +60,7 @@ tqueueReceiveSlot(TupleTableSlot *slot, DestReceiver *self) /* Send the tuple itself. */ tuple = ExecFetchSlotMinimalTuple(slot, &should_free); - result = shm_mq_send(tqueue->queue, tuple->t_len, tuple, false); + result = shm_mq_send(tqueue->queue, tuple->t_len, tuple, false, false); if (should_free) pfree(tuple); diff --git a/src/backend/libpq/pqmq.c b/src/backend/libpq/pqmq.c index d1a1f47a788..846494bf44c 100644 --- a/src/backend/libpq/pqmq.c +++ b/src/backend/libpq/pqmq.c @@ -154,7 +154,12 @@ mq_putmessage(char msgtype, const char *s, size_t len) for (;;) { - result = shm_mq_sendv(pq_mq_handle, iov, 2, true); + /* + * Immediately notify the receiver by passing force_flush as true so + * that the shared memory value is updated before we send the parallel + * message signal right after this. + */ + result = shm_mq_sendv(pq_mq_handle, iov, 2, true, true); if (pq_mq_parallel_leader_pid != 0) SendProcSignal(pq_mq_parallel_leader_pid, diff --git a/src/backend/storage/ipc/shm_mq.c b/src/backend/storage/ipc/shm_mq.c index 91a7093e033..b4ce9629d4c 100644 --- a/src/backend/storage/ipc/shm_mq.c +++ b/src/backend/storage/ipc/shm_mq.c @@ -109,6 +109,12 @@ struct shm_mq * locally by copying the chunks into a backend-local buffer. mqh_buffer is * the buffer, and mqh_buflen is the number of bytes allocated for it. * + * mqh_send_pending, is number of bytes that is written to the queue but not + * yet updated in the shared memory. We will not update it until the written + * data is 1/4th of the ring size or the tuple queue is full. This will + * prevent frequent CPU cache misses, and it will also avoid frequent + * SetLatch() calls, which are quite expensive. + * * mqh_partial_bytes, mqh_expected_bytes, and mqh_length_word_complete * are used to track the state of non-blocking operations. When the caller * attempts a non-blocking operation that returns SHM_MQ_WOULD_BLOCK, they @@ -137,6 +143,7 @@ struct shm_mq_handle char *mqh_buffer; Size mqh_buflen; Size mqh_consume_pending; + Size mqh_send_pending; Size mqh_partial_bytes; Size mqh_expected_bytes; bool mqh_length_word_complete; @@ -292,6 +299,7 @@ shm_mq_attach(shm_mq *mq, dsm_segment *seg, BackgroundWorkerHandle *handle) mqh->mqh_buffer = NULL; mqh->mqh_buflen = 0; mqh->mqh_consume_pending = 0; + mqh->mqh_send_pending = 0; mqh->mqh_partial_bytes = 0; mqh->mqh_expected_bytes = 0; mqh->mqh_length_word_complete = false; @@ -319,14 +327,15 @@ shm_mq_set_handle(shm_mq_handle *mqh, BackgroundWorkerHandle *handle) * Write a message into a shared message queue. */ shm_mq_result -shm_mq_send(shm_mq_handle *mqh, Size nbytes, const void *data, bool nowait) +shm_mq_send(shm_mq_handle *mqh, Size nbytes, const void *data, bool nowait, + bool force_flush) { shm_mq_iovec iov; iov.data = data; iov.len = nbytes; - return shm_mq_sendv(mqh, &iov, 1, nowait); + return shm_mq_sendv(mqh, &iov, 1, nowait, force_flush); } /* @@ -343,9 +352,15 @@ shm_mq_send(shm_mq_handle *mqh, Size nbytes, const void *data, bool nowait) * arguments, each time the process latch is set. (Once begun, the sending * of a message cannot be aborted except by detaching from the queue; changing * the length or payload will corrupt the queue.) + * + * When force_flush = true, we immediately update the shm_mq's mq_bytes_written + * and notify the receiver (if it is already attached). Otherwise, we don't + * update it until we have written an amount of data greater than 1/4th of the + * ring size. */ shm_mq_result -shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait) +shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait, + bool force_flush) { shm_mq_result res; shm_mq *mq = mqh->mqh_queue; @@ -518,8 +533,18 @@ shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait) mqh->mqh_counterparty_attached = true; } - /* Notify receiver of the newly-written data, and return. */ - SetLatch(&receiver->procLatch); + /* + * If the caller has requested force flush or we have written more than 1/4 + * of the ring size, mark it as written in shared memory and notify the + * receiver. + */ + if (force_flush || mqh->mqh_send_pending > (mq->mq_ring_size >> 2)) + { + shm_mq_inc_bytes_written(mq, mqh->mqh_send_pending); + SetLatch(&receiver->procLatch); + mqh->mqh_send_pending = 0; + } + return SHM_MQ_SUCCESS; } @@ -816,6 +841,13 @@ shm_mq_wait_for_attach(shm_mq_handle *mqh) void shm_mq_detach(shm_mq_handle *mqh) { + /* Before detaching, notify the receiver about any already-written data. */ + if (mqh->mqh_send_pending > 0) + { + shm_mq_inc_bytes_written(mqh->mqh_queue, mqh->mqh_send_pending); + mqh->mqh_send_pending = 0; + } + /* Notify counterparty that we're outta here. */ shm_mq_detach_internal(mqh->mqh_queue); @@ -894,7 +926,7 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, const void *data, /* Compute number of ring buffer bytes used and available. */ rb = pg_atomic_read_u64(&mq->mq_bytes_read); - wb = pg_atomic_read_u64(&mq->mq_bytes_written); + wb = pg_atomic_read_u64(&mq->mq_bytes_written) + mqh->mqh_send_pending; Assert(wb >= rb); used = wb - rb; Assert(used <= ringsize); @@ -951,6 +983,9 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, const void *data, } else if (available == 0) { + /* Update the pending send bytes in the shared memory. */ + shm_mq_inc_bytes_written(mq, mqh->mqh_send_pending); + /* * Since mq->mqh_counterparty_attached is known to be true at this * point, mq_receiver has been set, and it can't change once set. @@ -959,6 +994,12 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, const void *data, Assert(mqh->mqh_counterparty_attached); SetLatch(&mq->mq_receiver->procLatch); + /* + * We have just updated the mqh_send_pending bytes in the shared + * memory so reset it. + */ + mqh->mqh_send_pending = 0; + /* Skip manipulation of our latch if nowait = true. */ if (nowait) { @@ -1009,13 +1050,14 @@ shm_mq_send_bytes(shm_mq_handle *mqh, Size nbytes, const void *data, * MAXIMUM_ALIGNOF, and each read is as well. */ Assert(sent == nbytes || sendnow == MAXALIGN(sendnow)); - shm_mq_inc_bytes_written(mq, MAXALIGN(sendnow)); /* - * For efficiency, we don't set the reader's latch here. We'll do - * that only when the buffer fills up or after writing an entire - * message. + * For efficiency, we don't update the bytes written in the shared + * memory and also don't set the reader's latch here. Refer to + * the comments atop the shm_mq_handle structure for more + * information. */ + mqh->mqh_send_pending += MAXALIGN(sendnow); } } |