Introducing application and port shared memory queues.

The goal is to minimize the number of syscalls needed to deliver a message.

src/nxt_port_queue.h

@@ -0,0 +1,102 @@
+
+/*
+ * Copyright (C) NGINX, Inc.
+ */
+
+#ifndef _NXT_PORT_QUEUE_H_INCLUDED_
+#define _NXT_PORT_QUEUE_H_INCLUDED_
+
+
+#include <nxt_nncq.h>
+
+
+/* Using Numeric Naive Circular Queue as a backend. */
+
+#define NXT_PORT_QUEUE_SIZE      NXT_NNCQ_SIZE
+#define NXT_PORT_QUEUE_MSG_SIZE  31
+
+
+typedef struct {
+    uint8_t   size;
+    uint8_t   data[NXT_PORT_QUEUE_MSG_SIZE];
+} nxt_port_queue_item_t;
+
+
+typedef struct {
+    nxt_nncq_atomic_t      nitems;
+    nxt_nncq_t             free_items;
+    nxt_nncq_t             queue;
+    nxt_port_queue_item_t  items[NXT_PORT_QUEUE_SIZE];
+} nxt_port_queue_t;
+
+
+nxt_inline void
+nxt_port_queue_init(nxt_port_queue_t volatile *q)
+{
+    nxt_nncq_atomic_t  i;
+
+    nxt_nncq_init(&q->free_items);
+    nxt_nncq_init(&q->queue);
+
+    for (i = 0; i < NXT_PORT_QUEUE_SIZE; i++) {
+        nxt_nncq_enqueue(&q->free_items, i);
+    }
+
+    q->nitems = 0;
+}
+
+
+nxt_inline nxt_int_t
+nxt_port_queue_send(nxt_port_queue_t volatile *q, const void *p, uint8_t size,
+    int *notify)
+{
+    nxt_nncq_atomic_t      i;
+    nxt_port_queue_item_t  *qi;
+
+    i = nxt_nncq_dequeue(&q->free_items);
+    if (i == nxt_nncq_empty(&q->free_items)) {
+        *notify = 0;
+        return NXT_AGAIN;
+    }
+
+    qi = (nxt_port_queue_item_t *) &q->items[i];
+
+    qi->size = size;
+    nxt_memcpy(qi->data, p, size);
+
+    nxt_nncq_enqueue(&q->queue, i);
+
+    i = nxt_atomic_fetch_add(&q->nitems, 1);
+
+    *notify = (i == 0);
+
+    return NXT_OK;
+}
+
+
+nxt_inline ssize_t
+nxt_port_queue_recv(nxt_port_queue_t volatile *q, void *p)
+{
+    ssize_t                res;
+    nxt_nncq_atomic_t      i;
+    nxt_port_queue_item_t  *qi;
+
+    i = nxt_nncq_dequeue(&q->queue);
+    if (i == nxt_nncq_empty(&q->queue)) {
+        return -1;
+    }
+
+    qi = (nxt_port_queue_item_t *) &q->items[i];
+
+    res = qi->size;
+    nxt_memcpy(p, qi->data, qi->size);
+
+    nxt_nncq_enqueue(&q->free_items, i);
+
+    nxt_atomic_fetch_add(&q->nitems, -1);
+
+    return res;
+}
+
+
+#endif /* _NXT_PORT_QUEUE_H_INCLUDED_ */