Align thread priority with Linux defaults

Under Linux filesystem threads responsible for handling I/O are
normally created with the maximum priority.  Non-I/O filesystem
processes run with the default priority.  ZFS should adopt the
same priority scheme under Linux to maintain good performance
and so that it will complete fairly when other Linux filesystems
are active.  The priorities have been updated to the following:

$ ps -eLo rtprio,cls,pid,pri,nice,cmd | egrep 'z_|spl_|zvol|arc|dbu|meta'
     -  TS 10743  19 -20 [spl_kmem_cache]
     -  TS 10744  19 -20 [spl_system_task]
     -  TS 10745  19 -20 [spl_dynamic_tas]
     -  TS 10764  19   0 [dbu_evict]
     -  TS 10765  19   0 [arc_prune]
     -  TS 10766  19   0 [arc_reclaim]
     -  TS 10767  19   0 [arc_user_evicts]
     -  TS 10768  19   0 [l2arc_feed]
     -  TS 10769  39   0 [z_unmount]
     -  TS 10770  39 -20 [zvol]
     -  TS 11011  39 -20 [z_null_iss]
     -  TS 11012  39 -20 [z_null_int]
     -  TS 11013  39 -20 [z_rd_iss]
     -  TS 11014  39 -20 [z_rd_int_0]
     -  TS 11022  38 -19 [z_wr_iss]
     -  TS 11023  39 -20 [z_wr_iss_h]
     -  TS 11024  39 -20 [z_wr_int_0]
     -  TS 11032  39 -20 [z_wr_int_h]
     -  TS 11033  39 -20 [z_fr_iss_0]
     -  TS 11041  39 -20 [z_fr_int]
     -  TS 11042  39 -20 [z_cl_iss]
     -  TS 11043  39 -20 [z_cl_int]
     -  TS 11044  39 -20 [z_ioctl_iss]
     -  TS 11045  39 -20 [z_ioctl_int]
     -  TS 11046  39 -20 [metaslab_group_]
     -  TS 11050  19   0 [z_iput]
     -  TS 11121  38 -19 [z_wr_iss]

Note that under Linux the meaning of a processes priority is inverted
with respect to illumos.  High values on Linux indicate a _low_ priority
while high value on illumos indicate a _high_ priority.

In order to preserve the logical meaning of the minclsyspri and
maxclsyspri macros when they are used by the illumos wrapper functions
their values have been inverted.  This way when changes are merged
from upstream illumos we won't need to remember to invert the macro.
It could also lead to confusion.

This patch depends on https://github.com/zfsonlinux/spl/pull/466.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes #3607

diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index 7652a9cae157727cd417c9c4d107c0752fb0ccb6..4f7e3287f3da3fea051acdab27943771f6b1e28c 100644 (file)
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -233,6 +233,7 @@ typedef struct kthread {
        kt_did_t        t_tid;
        thread_func_t   t_func;
        void *          t_arg;
+       pri_t           t_pri;
 } kthread_t;
 
 #define        curthread                       zk_thread_current()
@@ -615,8 +616,12 @@ extern void delay(clock_t ticks);
 #define        max_ncpus       64
 #define        boot_ncpus      (sysconf(_SC_NPROCESSORS_ONLN))
 
-#define        minclsyspri     60
-#define        maxclsyspri     99
+/*
+ * Process priorities as defined by setpriority(2) and getpriority(2).
+ */
+#define        minclsyspri     19
+#define        maxclsyspri     -20
+#define        defclsyspri     0
 
 #define        CPU_SEQID       (pthread_self() & (max_ncpus - 1))
 

diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 80da41151c7022c5e2a08d3a746ec6fd59890eeb..a451026999c5657facc6d0ea55a75b8f631ba3e2 100644 (file)
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -128,6 +128,7 @@ zk_thread_helper(void *arg)
        VERIFY3S(pthread_mutex_lock(&kthread_lock), ==, 0);
        kthread_nr++;
        VERIFY3S(pthread_mutex_unlock(&kthread_lock), ==, 0);
+       (void) setpriority(PRIO_PROCESS, 0, kt->t_pri);
 
        kt->t_tid = pthread_self();
        ((thread_func_arg_t) kt->t_func)(kt->t_arg);
@@ -151,6 +152,7 @@ zk_thread_create(caddr_t stk, size_t stksize, thread_func_t func, void *arg,
        kt = umem_zalloc(sizeof (kthread_t), UMEM_NOFAIL);
        kt->t_func = func;
        kt->t_arg = arg;
+       kt->t_pri = pri;
 
        VERIFY0(pthread_attr_init(&attr));
        VERIFY0(pthread_attr_setdetachstate(&attr, detachstate));

diff --git a/lib/libzpool/taskq.c b/lib/libzpool/taskq.c
index 59b4c7c05f7950f42721464aae1fb083e055e9f7..bd92e61ab04db489f9ee7a147f158e85130cb151 100644 (file)
--- a/lib/libzpool/taskq.c
+++ b/lib/libzpool/taskq.c
@@ -308,7 +308,7 @@ taskq_create(const char *name, int nthreads, pri_t pri,
 
        for (t = 0; t < nthreads; t++)
                VERIFY((tq->tq_threadlist[t] = thread_create(NULL, 0,
-                   taskq_thread, tq, TS_RUN, NULL, 0, 0)) != NULL);
+                   taskq_thread, tq, TS_RUN, NULL, 0, pri)) != NULL);
 
        return (tq);
 }
@@ -371,7 +371,7 @@ taskq_cancel_id(taskq_t *tq, taskqid_t id)
 void
 system_taskq_init(void)
 {
-       system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
+       system_taskq = taskq_create("system_taskq", 64, maxclsyspri, 4, 512,
            TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 }
 

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 66e67795ff0b70992e7f5bc88288fce10c99e736..c2fdf16309c4ce5b445b4c84ec5cb9dc5722ec4e 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -5431,7 +5431,7 @@ arc_init(void)
        mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
        bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
 
-       arc_prune_taskq = taskq_create("arc_prune", max_ncpus, minclsyspri,
+       arc_prune_taskq = taskq_create("arc_prune", max_ncpus, defclsyspri,
            max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
 
        arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
@@ -5444,10 +5444,10 @@ arc_init(void)
        }
 
        (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
-           TS_RUN, minclsyspri);
+           TS_RUN, defclsyspri);
 
        (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0,
-           TS_RUN, minclsyspri);
+           TS_RUN, defclsyspri);
 
        arc_dead = FALSE;
        arc_warm = B_FALSE;
@@ -6954,7 +6954,7 @@ l2arc_start(void)
                return;
 
        (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
-           TS_RUN, minclsyspri);
+           TS_RUN, defclsyspri);
 }
 
 void

diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index c7b6a5d9aa0210220bab0769f1a6379d5fb2848e..3807418c97bfcd673c23ed4384fbcea1384e979a 100644 (file)
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -413,7 +413,7 @@ retry:
         * All entries are queued via taskq_dispatch_ent(), so min/maxalloc
         * configuration is not required.
         */
-       dbu_evict_taskq = taskq_create("dbu_evict", 1, minclsyspri, 0, 0, 0);
+       dbu_evict_taskq = taskq_create("dbu_evict", 1, defclsyspri, 0, 0, 0);
 }
 
 void

diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index 56a804dfb69d1ef724483806c2c346c99baf7b7e..4d5baf8da84b3f26b08f92cfb7106687776ce192 100644 (file)
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -1839,7 +1839,7 @@ dmu_objset_find_dp(dsl_pool_t *dp, uint64_t ddobj,
        ntasks = dmu_find_threads;
        if (ntasks == 0)
                ntasks = vdev_count_leaves(dp->dp_spa) * 4;
-       tq = taskq_create("dmu_objset_find", ntasks, minclsyspri, ntasks,
+       tq = taskq_create("dmu_objset_find", ntasks, maxclsyspri, ntasks,
            INT_MAX, 0);
        if (tq == NULL) {
                kmem_free(dcp, sizeof (*dcp));

diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c
index 23cf43862835a48188675d682c40d7c5c3d86c5d..ada0eac63eeaaea4ed1de7a74a98821982d47a02 100644 (file)
--- a/module/zfs/dsl_pool.c
+++ b/module/zfs/dsl_pool.c
@@ -170,7 +170,7 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg)
        mutex_init(&dp->dp_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&dp->dp_spaceavail_cv, NULL, CV_DEFAULT, NULL);
 
-       dp->dp_iput_taskq = taskq_create("z_iput", max_ncpus, minclsyspri,
+       dp->dp_iput_taskq = taskq_create("z_iput", max_ncpus, defclsyspri,
            max_ncpus * 8, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
 
        return (dp);

diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 5544859b68eff5728a22fdddb3f597b28c32ca4f..b328cbb0a106262e81a7b71444e6b6005fc18102 100644 (file)
--- a/module/zfs/metaslab.c
+++ b/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 | TASKQ_DYNAMIC);
+           maxclsyspri, 10, INT_MAX, TASKQ_THREADS_CPU_PCT | TASKQ_DYNAMIC);
 
        return (mg);
 }

diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index d8eaf9979fafefd53eb6f868c2d43fcd207cd476..2e23a341fb13119ecd98902715543e53c038834f 100644 (file)
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -898,11 +898,13 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
                        pri_t pri = maxclsyspri;
                        /*
                         * The write issue taskq can be extremely CPU
-                        * intensive.  Run it at slightly lower priority
-                        * than the other taskqs.
+                        * intensive.  Run it at slightly less important
+                        * priority than the other taskqs.  Under Linux this
+                        * means incrementing the priority value on platforms
+                        * like illumos it should be decremented.
                         */
                        if (t == ZIO_TYPE_WRITE && q == ZIO_TASKQ_ISSUE)
-                               pri--;
+                               pri++;
 
                        tq = taskq_create_proc(name, value, pri, 50,
                            INT_MAX, spa->spa_proc, flags);

diff --git a/module/zfs/txg.c b/module/zfs/txg.c
index 7681856ea14098d77fe4d1ce6019953566c65a99..1d5ee97b1368d9c5fe56274abed4cae4b2c74002 100644 (file)
--- a/module/zfs/txg.c
+++ b/module/zfs/txg.c
@@ -205,7 +205,7 @@ txg_sync_start(dsl_pool_t *dp)
        tx->tx_threads = 2;
 
        tx->tx_quiesce_thread = thread_create(NULL, 0, txg_quiesce_thread,
-           dp, 0, &p0, TS_RUN, minclsyspri);
+           dp, 0, &p0, TS_RUN, defclsyspri);
 
        /*
         * The sync thread can need a larger-than-default stack size on
@@ -213,7 +213,7 @@ txg_sync_start(dsl_pool_t *dp)
         * scrub_visitbp() recursion.
         */
        tx->tx_sync_thread = thread_create(NULL, 32<<10, txg_sync_thread,
-           dp, 0, &p0, TS_RUN, minclsyspri);
+           dp, 0, &p0, TS_RUN, defclsyspri);
 
        mutex_exit(&tx->tx_sync_lock);
 }
@@ -445,7 +445,7 @@ 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",
-                           max_ncpus, minclsyspri, max_ncpus, max_ncpus * 2,
+                           max_ncpus, defclsyspri, max_ncpus, max_ncpus * 2,
                            TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
                }
 

diff --git a/module/zfs/zfs_ctldir.c b/module/zfs/zfs_ctldir.c
index 59405de82b00f1831d4944e7f9de23f8fc29ee9d..efa6cfa0a4cab1b624703dddda9509cd591d6eec 100644 (file)
--- a/module/zfs/zfs_ctldir.c
+++ b/module/zfs/zfs_ctldir.c
@@ -1009,7 +1009,7 @@ zfsctl_shares_lookup(struct inode *dip, char *name, struct inode **ipp,
 void
 zfsctl_init(void)
 {
-       zfs_expire_taskq = taskq_create("z_unmount", 1, maxclsyspri,
+       zfs_expire_taskq = taskq_create("z_unmount", 1, defclsyspri,
            1, 8, TASKQ_PREPOPULATE);
 }
 

diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index 6a3885816cb03f8230d1d6b73c0a923c5d5ccacf..289b23c7f488a44755be6c59f4929ac0b618ff36 100644 (file)
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -1888,7 +1888,7 @@ zil_open(objset_t *os, zil_get_data_t *get_data)
        ASSERT(list_is_empty(&zilog->zl_lwb_list));
 
        zilog->zl_get_data = get_data;
-       zilog->zl_clean_taskq = taskq_create("zil_clean", 1, minclsyspri,
+       zilog->zl_clean_taskq = taskq_create("zil_clean", 1, defclsyspri,
            2, 2, TASKQ_PREPOPULATE);
 
        return (zilog);