smalloc: bump initial size to 8 pools

Commit 23bd40f shrank our pool size from 128 pools at 8MB max,
to one static 16MB pool. Christian reports:

"For our tests with about 250k files we found the smalloc pool being
 depleted.  Now for us values of 3-4 would be enough, but since it is a
 compile time switch I'd like to make it safe for everybody and set 8."

Bump the pool alloc to 8 pools again, retaining the 16MB size. That's
still substantially less than before, but should be enough for most
cases. Allocate the pools at init time, to avoid the issue that the
original commit fixed.

Also fix a bug where we failed to iterate some pools when restarting
the allocation scan, resulting in less-than-optimal exhaustion of all
pools before smalloc() gave up and returned NULL.

Signed-off-by: Jens Axboe <[email protected]>

smalloc.c

@@ -26,7 +26,7 @@
 #define SMALLOC_BPL	(SMALLOC_BPB * SMALLOC_BPI)
 
 #define INITIAL_SIZE	16*1024*1024	/* new pool size */
-#define MAX_POOLS	1		/* maximum number of pools to setup */
+#define MAX_POOLS	8		/* maximum number of pools to setup */
 
 #define SMALLOC_PRE_RED		0xdeadbeefU
 #define SMALLOC_POST_RED	0x5aa55aa5U
@@ -230,11 +230,21 @@ static int add_pool(struct pool *pool, unsigned int alloc_size)
 
 void sinit(void)
 {
-	int ret;
+	int i, ret;
 
 	lock = fio_rwlock_init();
-	ret = add_pool(&mp[0], INITIAL_SIZE);
-	assert(!ret);
+
+	for (i = 0; i < MAX_POOLS; i++) {
+		ret = add_pool(&mp[i], INITIAL_SIZE);
+		if (ret)
+			break;
+	}
+
+	/*
+	 * If we added at least one pool, we should be OK for most
+	 * cases.
+	 */
+	assert(i);
 }
 
 static void cleanup_pool(struct pool *pool)
@@ -442,16 +452,17 @@ static void *smalloc_pool(struct pool *pool, size_t size)
 
 void *smalloc(size_t size)
 {
-	unsigned int i;
+	unsigned int i, end_pool;
 
 	if (size != (unsigned int) size)
 		return NULL;
 
 	global_write_lock();
 	i = last_pool;
+	end_pool = nr_pools;
 
 	do {
-		for (; i < nr_pools; i++) {
+		for (; i < end_pool; i++) {
 			void *ptr = smalloc_pool(&mp[i], size);
 
 			if (ptr) {
@@ -461,20 +472,14 @@ void *smalloc(size_t size)
 			}
 		}
 		if (last_pool) {
-			last_pool = 0;
+			end_pool = last_pool;
+			last_pool = i = 0;
 			continue;
 		}
 
-		if (nr_pools + 1 > MAX_POOLS)
-			break;
-		else {
-			i = nr_pools;
-			if (add_pool(&mp[nr_pools], size))
-				goto out;
-		}
+		break;
 	} while (1);
 
-out:
 	global_write_unlock();
 	return NULL;
 }