[tarantool-patches] [PATCH v2 6/8] Offload tx_prio processing to a fiber

[Georgy Kirichenko <georgy@tarantool.org>]

---
 src/box/box.cc | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/box/box.cc b/src/box/box.cc
index e10b73277..b8ef4b9ed 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -2061,13 +2061,41 @@ local_recovery(const struct tt_uuid *instance_uuid,
 	}
 }
 
+/* A structure containing tx_prio endpoint fiber context. */
+static struct tx_prio_ctx {
+	/* The fiber processing the tx_prio endpoint. */
+	struct fiber *fiber;
+	/* True if there are more messages to process. */
+	bool has_message;
+	/* Condition to signal when a new message arrived. */
+	struct fiber_cond message_cond;
+} tx_prio_ctx;
+
 static void
 tx_prio_cb(struct ev_loop *loop, ev_watcher *watcher, int events)
 {
 	(void) loop;
 	(void) events;
-	struct cbus_endpoint *endpoint = (struct cbus_endpoint *)watcher->data;
-	cbus_process(endpoint);
+	(void) watcher;
+	tx_prio_ctx.has_message = true;
+	fiber_cond_signal(&tx_prio_ctx.message_cond);
+}
+
+/*
+ * Tx prio endpoint fiber function.
+ */
+static int
+tx_prio_process_f(va_list ap)
+{
+	(void) ap;
+	while (!fiber_is_cancelled()) {
+		while (tx_prio_ctx.has_message) {
+			tx_prio_ctx.has_message = false;
+			cbus_process(&tx_prio_endpoint);
+		}
+		fiber_cond_wait(&tx_prio_ctx.message_cond);
+	}
+	return 0;
 }
 
 static void
@@ -2119,6 +2147,12 @@ box_cfg_xc(void)
 			  IPROTO_MSG_MAX_MIN * IPROTO_FIBER_POOL_SIZE_FACTOR,
 			  FIBER_POOL_IDLE_TIMEOUT);
 	/* Add an extra endpoint for WAL wake up/rollback messages. */
+	memset(&tx_prio_ctx, 0, sizeof(struct tx_prio_ctx));
+	fiber_cond_create(&tx_prio_ctx.message_cond);
+	tx_prio_ctx.fiber = fiber_new("tx_prio", tx_prio_process_f);
+	if (tx_prio_ctx.fiber == NULL)
+		panic("Could not create tx_prio fiber");
+	fiber_start(tx_prio_ctx.fiber, NULL);
 	cbus_endpoint_create(&tx_prio_endpoint, "tx_prio", tx_prio_cb, &tx_prio_endpoint);
 
 	rmean_box = rmean_new(iproto_type_strs, IPROTO_TYPE_STAT_MAX);
-- 
2.21.0