Update all default taskq settings

Over the years the default values for the taskqs used on Linux have
differed slightly from illumos.  In the vast majority of cases this
was done to avoid creating an obnoxious number of idle threads which
would pollute the process listing.

With the addition of support for dynamic taskqs all multi-threaded
queues should be created as dynamic taskqs.  This allows us to get
the best of both worlds.

* The illumos default values for the I/O pipeline can be restored.
These values are known to work well for most workloads.  The only
exception is the zio write interrupt taskq which is changed to
ZTI_P(12, 8).  At least under Linux more threads has been shown
to improve performance, see commit 7e55f4e.

* Reduces the number of idle threads on the system when it's not
under heavy load.  The maximum number of threads will only be
created when they are required.

* Remove the vdev_file_taskq and rely on the system_taskq instead
which is now dynamic and may have up to 64-threads.  Again this
brings us back inline with upstream.

* Tasks dispatched with taskq_dispatch_ent() are allowed to use
dynamic taskqs.  The Linux taskq implementation supports this.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes #3507

Author: behlendorf

include/sys/vdev_file.h

@@ -27,8 +27,6 @@
 #ifndef _SYS_VDEV_FILE_H
 #define	_SYS_VDEV_FILE_H
 
-
-
 #include <sys/vdev.h>
 
 #ifdef	__cplusplus
@@ -39,9 +37,6 @@ typedef struct vdev_file {
 	vnode_t		*vf_vnode;
 } vdev_file_t;
 
-extern void vdev_file_init(void);
-extern void vdev_file_fini(void);
-
 #ifdef	__cplusplus
 }
 #endif

lib/libzpool/taskq.c

@@ -178,7 +178,6 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
     taskq_ent_t *t)
 {
 	ASSERT(func != NULL);
-	ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC));
 
 	/*
 	 * Mark it as a prealloc'd task.  This is important

module/zfs/arc.c

@@ -5002,7 +5002,7 @@ arc_init(void)
 	bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
 
 	arc_prune_taskq = taskq_create("arc_prune", max_ncpus, minclsyspri,
-	    max_ncpus, INT_MAX, TASKQ_PREPOPULATE);
+	    max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
 
 	arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
 	    sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);

module/zfs/dsl_pool.c

@@ -171,7 +171,7 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg)
 	cv_init(&dp->dp_spaceavail_cv, NULL, CV_DEFAULT, NULL);
 
 	dp->dp_iput_taskq = taskq_create("z_iput", max_ncpus, minclsyspri,
-	    max_ncpus * 8, INT_MAX, TASKQ_PREPOPULATE);
+	    max_ncpus * 8, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
 
 	return (dp);
 }

module/zfs/metaslab.c

@@ -492,7 +492,7 @@ metaslab_group_create(metaslab_class_t *mc, vdev_t *vd)
 	mg->mg_activation_count = 0;
 
 	mg->mg_taskq = taskq_create("metaslab_group_taskq", metaslab_load_pct,
-	    minclsyspri, 10, INT_MAX, TASKQ_THREADS_CPU_PCT);
+	    minclsyspri, 10, INT_MAX, TASKQ_THREADS_CPU_PCT | TASKQ_DYNAMIC);
 
 	return (mg);
 }

module/zfs/spa.c

@@ -127,9 +127,9 @@ static const char *const zio_taskq_types[ZIO_TASKQ_TYPES] = {
 const zio_taskq_info_t zio_taskqs[ZIO_TYPES][ZIO_TASKQ_TYPES] = {
 	/* ISSUE	ISSUE_HIGH	INTR		INTR_HIGH */
 	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL }, /* NULL */
-	{ ZTI_N(8),	ZTI_NULL,	ZTI_BATCH,	ZTI_NULL }, /* READ */
-	{ ZTI_BATCH,	ZTI_N(5),	ZTI_N(16),	ZTI_N(5) }, /* WRITE */
-	{ ZTI_P(4, 8),	ZTI_NULL,	ZTI_ONE,	ZTI_NULL }, /* FREE */
+	{ ZTI_N(8),	ZTI_NULL,	ZTI_P(12, 8),	ZTI_NULL }, /* READ */
+	{ ZTI_BATCH,	ZTI_N(5),	ZTI_P(12, 8),	ZTI_N(5) }, /* WRITE */
+	{ ZTI_P(12, 8),	ZTI_NULL,	ZTI_ONE,	ZTI_NULL }, /* FREE */
 	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL }, /* CLAIM */
 	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL }, /* IOCTL */
 };
@@ -844,7 +844,7 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
 	uint_t count = ztip->zti_count;
 	spa_taskqs_t *tqs = &spa->spa_zio_taskq[t][q];
 	char name[32];
-	uint_t i, flags = 0;
+	uint_t i, flags = TASKQ_DYNAMIC;
 	boolean_t batch = B_FALSE;
 
 	if (mode == ZTI_MODE_NULL) {

module/zfs/spa_misc.c

@@ -1829,7 +1829,6 @@ spa_init(int mode)
 	dmu_init();
 	zil_init();
 	vdev_cache_stat_init();
-	vdev_file_init();
 	zfs_prop_init();
 	zpool_prop_init();
 	zpool_feature_init();
@@ -1844,7 +1843,6 @@ spa_fini(void)
 
 	spa_evict_all();
 
-	vdev_file_fini();
 	vdev_cache_stat_fini();
 	zil_fini();
 	dmu_fini();

module/zfs/txg.c

@@ -445,8 +445,8 @@ txg_dispatch_callbacks(dsl_pool_t *dp, uint64_t txg)
 			 * Commit callback taskq hasn't been created yet.
 			 */
 			tx->tx_commit_cb_taskq = taskq_create("tx_commit_cb",
-			    100, minclsyspri, max_ncpus, INT_MAX,
-			    TASKQ_THREADS_CPU_PCT | TASKQ_PREPOPULATE);
+			    max_ncpus, minclsyspri, max_ncpus, max_ncpus * 2,
+			    TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
 		}
 
 		cb_list = kmem_alloc(sizeof (list_t), KM_SLEEP);

module/zfs/vdev_file.c

@@ -36,8 +36,6 @@
  * Virtual device vector for files.
  */
 
-static taskq_t *vdev_file_taskq;
-
 static void
 vdev_file_hold(vdev_t *vd)
 {
@@ -200,7 +198,7 @@ vdev_file_io_start(zio_t *zio)
 			 * the sync must be dispatched to a different context.
 			 */
 			if (spl_fstrans_check()) {
-				VERIFY3U(taskq_dispatch(vdev_file_taskq,
+				VERIFY3U(taskq_dispatch(system_taskq,
 				    vdev_file_io_fsync, zio, TQ_SLEEP), !=, 0);
 				return;
 			}
@@ -216,7 +214,7 @@ vdev_file_io_start(zio_t *zio)
 		return;
 	}
 
-	VERIFY3U(taskq_dispatch(vdev_file_taskq, vdev_file_io_strategy, zio,
+	VERIFY3U(taskq_dispatch(system_taskq, vdev_file_io_strategy, zio,
 	    TQ_SLEEP), !=, 0);
 }
 
@@ -239,21 +237,6 @@ vdev_ops_t vdev_file_ops = {
 	B_TRUE			/* leaf vdev */
 };
 
-void
-vdev_file_init(void)
-{
-	vdev_file_taskq = taskq_create("vdev_file_taskq", 100, minclsyspri,
-	    max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_THREADS_CPU_PCT);
-
-	VERIFY(vdev_file_taskq);
-}
-
-void
-vdev_file_fini(void)
-{
-	taskq_destroy(vdev_file_taskq);
-}
-
 /*
  * From userland we access disks just like files.
  */

module/zfs/zvol.c

@@ -1632,7 +1632,7 @@ zvol_init(void)
 	mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);
 
 	zvol_taskq = taskq_create(ZVOL_DRIVER, zvol_threads, maxclsyspri,
-	    zvol_threads, INT_MAX, TASKQ_PREPOPULATE);
+	    zvol_threads * 2, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
 	if (zvol_taskq == NULL) {
 		printk(KERN_INFO "ZFS: taskq_create() failed\n");
 		error = -ENOMEM;