daemon/worker: ring buffer to recycle mempools

this avoids repetitive allocation/free cycles on load

daemon/engine.h

@@ -20,6 +20,9 @@
 #ifndef DEFAULT_NSREP_SIZE
 #define DEFAULT_NSREP_SIZE 4096 /**< Default NS reputation cache size */
 #endif
+#ifndef DEFAULT_RING_SIZE
+#define DEFAULT_RING_SIZE 16 /**< Maximum size of the worker ring size */
+#endif
 
 /*
  * @internal These are forward decls to allow building modules with engine but without Lua.

daemon/main.c

@@ -150,6 +150,8 @@ int main(int argc, char **argv)
 		.mm = NULL
 	};
 	loop->data = &worker;
+	array_init(worker.bufs.ring);
+	worker_reserve(&worker, DEFAULT_RING_SIZE);
 
 	/* Bind to sockets. */
 	if (addr != NULL) {
@@ -182,6 +184,7 @@ int main(int argc, char **argv)
 	/* Cleanup. */
 	fprintf(stderr, "\n[system] quitting\n");
 	engine_deinit(&engine);
+	worker_reclaim(&worker);
 
 	if (ret != 0) {
 		ret = EXIT_FAILURE;

daemon/worker.c

@@ -27,6 +27,7 @@
 struct qr_task
 {
 	struct kr_request req;
+	struct worker_ctx *worker;
 	knot_pkt_t *next_query;
 	uv_handle_t *next_handle;
 	uv_timer_t timeout;
@@ -62,8 +63,15 @@ static int parse_query(knot_pkt_t *query)
 
 static struct qr_task *qr_task_create(struct worker_ctx *worker, uv_handle_t *handle, knot_pkt_t *query, const struct sockaddr *addr)
 {
+	/* Recycle mempool from ring or create it */
 	mm_ctx_t pool;
-	mm_ctx_mempool(&pool, MM_DEFAULT_BLKSIZE);
+	mempool_ring_t *ring = &worker->bufs.ring;
+	if (ring->len > 0) {
+		pool = array_tail(*ring);
+		array_pop(*ring);
+	} else {
+		mm_ctx_mempool(&pool, KNOT_WIRE_MAX_PKTSIZE);
+	}
 
 	/* Create worker task */
 	struct engine *engine = worker->engine;
@@ -73,6 +81,7 @@ static struct qr_task *qr_task_create(struct worker_ctx *worker, uv_handle_t *ha
 		mp_delete(pool.ctx);
 		return NULL;
 	}
+	task->worker = worker;
 	task->req.pool = pool;
 	task->source.handle = handle;
 	if (addr) {
@@ -118,7 +127,15 @@ static void qr_task_free(uv_handle_t *handle)
 		uv_ref(task->source.handle);
 		io_start_read(task->source.handle);
 	}
-	mp_delete(task->req.pool.ctx);
+	/* Return mempool to ring or free it if it's full */
+	struct worker_ctx *worker = task->worker;
+	mempool_ring_t *ring = &worker->bufs.ring;
+	if (ring->len < ring->cap) {
+		mp_flush(task->req.pool.ctx);
+		array_push(*ring, task->req.pool);
+	} else {
+		mp_delete(task->req.pool.ctx);
+	}
 }
 
 static void qr_task_timeout(uv_timer_t *req)
@@ -262,3 +279,17 @@ int worker_exec(struct worker_ctx *worker, uv_handle_t *handle, knot_pkt_t *quer
 	/* Consume input and produce next query */
 	return qr_task_step(task, query);
 }
+
+int worker_reserve(struct worker_ctx *worker, size_t ring_maxlen)
+{
+	return array_reserve(worker->bufs.ring, ring_maxlen);
+}
+
+void worker_reclaim(struct worker_ctx *worker)
+{
+	mempool_ring_t *ring = &worker->bufs.ring;
+	for (unsigned i = 0; i < ring->len; ++i) {
+		mp_delete(ring->at[i].ctx);
+	}
+	array_clear(*ring);
+}

daemon/worker.h

@@ -19,6 +19,9 @@
 #include <libknot/internal/mempattern.h>
 
 #include "daemon/engine.h"
+#include "lib/generic/array.h"
+
+typedef array_t(mm_ctx_t) mempool_ring_t;
 
 /**
  * Query resolution worker.
@@ -29,6 +32,7 @@ struct worker_ctx {
 	mm_ctx_t *mm;
 	struct {
 		uint8_t wire[KNOT_WIRE_MAX_PKTSIZE];
+		mempool_ring_t ring;
 	} bufs;
 };
 
@@ -43,3 +47,9 @@ struct worker_ctx {
  * @return 0, error code
  */
 int worker_exec(struct worker_ctx *worker, uv_handle_t *handle, knot_pkt_t *query, const struct sockaddr* addr);
+
+/** Reserve worker buffers */
+int worker_reserve(struct worker_ctx *worker, size_t ring_maxlen);
+
+/** Collect worker mempools */
+void worker_reclaim(struct worker_ctx *worker);