Add new kstat for monitoring time in dmu_tx_assign
This change adds a new kstat to gain some visibility into the amount of
time spent in each call to dmu_tx_assign. A histogram is exported via
a new dmu_tx_assign_histogram-$POOLNAME file. The information contained
in this histogram is the frequency dmu_tx_assign took to complete given
an interval range. For example, given the below histogram file:
$ cat /proc/spl/kstat/zfs/dmu_tx_assign_histogram-tank
12 1 0x01 32 1536 19792068076691 20516481514522
name type data
1 us 4 859
2 us 4 252
4 us 4 171
8 us 4 2
16 us 4 0
32 us 4 2
64 us 4 0
128 us 4 0
256 us 4 0
512 us 4 0
1024 us 4 0
2048 us 4 0
4096 us 4 0
8192 us 4 0
16384 us 4 0
32768 us 4 1
65536 us 4 1
131072 us 4 1
262144 us 4 4
524288 us 4 0
1048576 us 4 0
2097152 us 4 0
4194304 us 4 0
8388608 us 4 0
16777216 us 4 0
33554432 us 4 0
67108864 us 4 0
134217728 us 4 0
268435456 us 4 0
536870912 us 4 0
1073741824 us 4 0
2147483648 us 4 0
one can see most calls to dmu_tx_assign completed in 32us or less, but a
few outliers did not. Specifically, 4 of the calls took between 262144us
and 131072us. This information is difficult, if not impossible, to gather
without this change.
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1584
This commit is contained in:
Prakash Surya
Brian Behlendorf
parent
bf89c19914
commit
92334b14ec
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@ -89,6 +89,7 @@ typedef struct dsl_pool {
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uint64_t dp_root_dir_obj;
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struct taskq *dp_iput_taskq;
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kstat_t *dp_txg_kstat;
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kstat_t *dp_tx_assign_kstat;
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/* No lock needed - sync context only */
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blkptr_t dp_meta_rootbp;
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@ -111,6 +112,8 @@ typedef struct dsl_pool {
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uint64_t dp_mos_uncompressed_delta;
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uint64_t dp_txg_history_size;
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list_t dp_txg_history;
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uint64_t dp_tx_assign_size;
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kstat_named_t *dp_tx_assign_buckets;
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/* Has its own locking */
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@ -162,6 +165,8 @@ extern int dsl_pool_user_release(dsl_pool_t *dp, uint64_t dsobj,
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extern void dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp);
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int dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **);
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void dsl_pool_tx_assign_add_usecs(dsl_pool_t *dp, uint64_t usecs);
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txg_history_t *dsl_pool_txg_history_add(dsl_pool_t *dp, uint64_t txg);
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txg_history_t *dsl_pool_txg_history_get(dsl_pool_t *dp, uint64_t txg);
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void dsl_pool_txg_history_put(txg_history_t *th);
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@ -1089,12 +1089,15 @@ dmu_tx_unassign(dmu_tx_t *tx)
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int
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dmu_tx_assign(dmu_tx_t *tx, uint64_t txg_how)
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{
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hrtime_t before, after;
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int err;
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ASSERT(tx->tx_txg == 0);
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ASSERT(txg_how != 0);
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ASSERT(!dsl_pool_sync_context(tx->tx_pool));
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before = gethrtime();
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while ((err = dmu_tx_try_assign(tx, txg_how)) != 0) {
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dmu_tx_unassign(tx);
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@ -1106,6 +1109,11 @@ dmu_tx_assign(dmu_tx_t *tx, uint64_t txg_how)
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txg_rele_to_quiesce(&tx->tx_txgh);
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after = gethrtime();
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dsl_pool_tx_assign_add_usecs(tx->tx_pool,
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(after - before) / NSEC_PER_USEC);
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return (0);
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}
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@ -58,6 +58,63 @@ kmutex_t zfs_write_limit_lock;
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static pgcnt_t old_physmem = 0;
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static void
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dsl_pool_tx_assign_init(dsl_pool_t *dp, unsigned int ndata)
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{
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kstat_named_t *ks;
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char name[KSTAT_STRLEN];
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int i, data_size = ndata * sizeof(kstat_named_t);
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(void) snprintf(name, KSTAT_STRLEN, "dmu_tx_assign-%s",
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spa_name(dp->dp_spa));
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dp->dp_tx_assign_size = ndata;
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if (data_size)
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dp->dp_tx_assign_buckets = kmem_alloc(data_size, KM_SLEEP);
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else
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dp->dp_tx_assign_buckets = NULL;
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for (i = 0; i < dp->dp_tx_assign_size; i++) {
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ks = &dp->dp_tx_assign_buckets[i];
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ks->data_type = KSTAT_DATA_UINT64;
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ks->value.ui64 = 0;
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(void) snprintf(ks->name, KSTAT_STRLEN, "%u us", 1 << i);
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}
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dp->dp_tx_assign_kstat = kstat_create("zfs", 0, name, "misc",
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KSTAT_TYPE_NAMED, 0, KSTAT_FLAG_VIRTUAL);
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if (dp->dp_tx_assign_kstat) {
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dp->dp_tx_assign_kstat->ks_data = dp->dp_tx_assign_buckets;
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dp->dp_tx_assign_kstat->ks_ndata = dp->dp_tx_assign_size;
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dp->dp_tx_assign_kstat->ks_data_size = data_size;
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kstat_install(dp->dp_tx_assign_kstat);
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}
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}
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static void
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dsl_pool_tx_assign_destroy(dsl_pool_t *dp)
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{
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if (dp->dp_tx_assign_buckets)
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kmem_free(dp->dp_tx_assign_buckets,
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dp->dp_tx_assign_size * sizeof(kstat_named_t));
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if (dp->dp_tx_assign_kstat)
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kstat_delete(dp->dp_tx_assign_kstat);
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}
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void
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dsl_pool_tx_assign_add_usecs(dsl_pool_t *dp, uint64_t usecs)
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{
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uint64_t idx = 0;
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while (((1 << idx) < usecs) && (idx < dp->dp_tx_assign_size - 1))
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idx++;
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atomic_inc_64(&dp->dp_tx_assign_buckets[idx].value.ui64);
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}
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static int
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dsl_pool_txg_history_update(kstat_t *ksp, int rw)
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{
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@ -238,6 +295,7 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg)
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1, 4, 0);
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dsl_pool_txg_history_init(dp, txg);
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dsl_pool_tx_assign_init(dp, 32);
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return (dp);
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}
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@ -379,6 +437,7 @@ dsl_pool_close(dsl_pool_t *dp)
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arc_flush(dp->dp_spa);
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txg_fini(dp);
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dsl_scan_fini(dp);
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dsl_pool_tx_assign_destroy(dp);
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dsl_pool_txg_history_destroy(dp);
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rw_destroy(&dp->dp_config_rwlock);
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mutex_destroy(&dp->dp_lock);
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