Analyze perf output and address two hotspots.

This patch gives up to 200 000 extra rps in wal_mode=none on
my laptop (1 450 000 vs. 1 250 000, nosqlbench 10x1000 batch workload)

src/box/schema.cc

@@ -31,7 +31,6 @@
 #include "schema.h"
 #include "user_def.h"
 #include "engine.h"
-#include "space.h"
 #include "memtx_index.h"
 #include "func.h"
 #include "tuple.h"

src/box/schema.h

@@ -69,6 +69,7 @@ enum {
 
 #include "error.h"
 #include <stdio.h> /* snprintf */
+#include "space.h"
 
 extern uint32_t sc_version;
 
@@ -94,9 +95,16 @@ space_name_by_id(uint32_t id);
 static inline struct space *
 space_cache_find(uint32_t id)
 {
-	struct space *space = space_by_id(id);
-	if (space)
+	static uint32_t scv = 0;
+	static struct space *space = NULL;
+	if (scv != sc_version)
+		space = NULL;
+	if (space && space->def.id == id)
 		return space;
+	if ((space = space_by_id(id))) {
+		scv = sc_version;
+		return space;
+	}
 	tnt_raise(ClientError, ER_NO_SUCH_SPACE, int2str(id));
 }
 

src/cbus.c

@@ -50,6 +50,8 @@ fiber_pool_f(va_list ap)
 {
 	struct fiber_pool *pool = va_arg(ap, struct fiber_pool *);
 	struct stailq *output = va_arg(ap, struct stailq *);
+	struct ev_loop *loop = va_arg(ap, struct ev_loop *);
+	struct ev_async *watcher = va_arg(ap, struct ev_async *);
 	pool->size++;
 	bool was_empty;
 restart:
@@ -59,7 +61,13 @@ fiber_pool_f(va_list ap)
 		while (! stailq_empty(output))
 			cmsg_deliver(stailq_shift_entry(output, struct cmsg, fifo));
 		/* fiber_yield_timeout() is expensive, avoid under load. */
-		fiber_sleep(0);
+		if (ev_is_pending(watcher)) {
+			struct cpipe *pipe = (struct cpipe *) watcher->data;
+			(void) cpipe_peek(pipe);
+			ev_clear_pending(loop, watcher);
+		} else {
+			fiber_reschedule();
+		}
 	}
 
 	/** Put the current fiber into a fiber cache. */
@@ -75,7 +83,6 @@ fiber_pool_f(va_list ap)
 static void
 fiber_pool_cb(ev_loop *loop, struct ev_async *watcher, int events)
 {
-	(void) loop;
 	(void) events;
 	struct cpipe *pipe = (struct cpipe *) watcher->data;
 	struct fiber_pool *pool = &pipe->pool;
@@ -92,7 +99,7 @@ fiber_pool_cb(ev_loop *loop, struct ev_async *watcher, int events)
 				error_log(diag_last_error(&fiber()->diag));
 				break;
 			}
-			fiber_start(f, pool, &pipe->output);
+			fiber_start(f, pool, &pipe->output, loop, watcher);
 		} else {
 			/**
 			 * No worries that this watcher may not