*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013 Steven Hartland. All rights reserved.
*/
#include <sys/dsl_pool.h>
#include <sys/zil_impl.h>
#include <sys/dsl_userhold.h>
-int zfs_no_write_throttle = 0;
-int zfs_write_limit_shift = 3; /* 1/8th of physical memory */
-int zfs_txg_synctime_ms = 1000; /* target millisecs to sync a txg */
+/*
+ * ZFS Write Throttle
+ * ------------------
+ *
+ * ZFS must limit the rate of incoming writes to the rate at which it is able
+ * to sync data modifications to the backend storage. Throttling by too much
+ * creates an artificial limit; throttling by too little can only be sustained
+ * for short periods and would lead to highly lumpy performance. On a per-pool
+ * basis, ZFS tracks the amount of modified (dirty) data. As operations change
+ * data, the amount of dirty data increases; as ZFS syncs out data, the amount
+ * of dirty data decreases. When the amount of dirty data exceeds a
+ * predetermined threshold further modifications are blocked until the amount
+ * of dirty data decreases (as data is synced out).
+ *
+ * The limit on dirty data is tunable, and should be adjusted according to
+ * both the IO capacity and available memory of the system. The larger the
+ * window, the more ZFS is able to aggregate and amortize metadata (and data)
+ * changes. However, memory is a limited resource, and allowing for more dirty
+ * data comes at the cost of keeping other useful data in memory (for example
+ * ZFS data cached by the ARC).
+ *
+ * Implementation
+ *
+ * As buffers are modified dsl_pool_willuse_space() increments both the per-
+ * txg (dp_dirty_pertxg[]) and poolwide (dp_dirty_total) accounting of
+ * dirty space used; dsl_pool_dirty_space() decrements those values as data
+ * is synced out from dsl_pool_sync(). While only the poolwide value is
+ * relevant, the per-txg value is useful for debugging. The tunable
+ * zfs_dirty_data_max determines the dirty space limit. Once that value is
+ * exceeded, new writes are halted until space frees up.
+ *
+ * The zfs_dirty_data_sync tunable dictates the threshold at which we
+ * ensure that there is a txg syncing (see the comment in txg.c for a full
+ * description of transaction group stages).
+ *
+ * The IO scheduler uses both the dirty space limit and current amount of
+ * dirty data as inputs. Those values affect the number of concurrent IOs ZFS
+ * issues. See the comment in vdev_queue.c for details of the IO scheduler.
+ *
+ * The delay is also calculated based on the amount of dirty data. See the
+ * comment above dmu_tx_delay() for details.
+ */
-unsigned long zfs_write_limit_min = 32 << 20; /* min write limit is 32MB */
-unsigned long zfs_write_limit_max = 0; /* max data payload per txg */
-unsigned long zfs_write_limit_inflated = 0;
-unsigned long zfs_write_limit_override = 0;
+/*
+ * zfs_dirty_data_max will be set to zfs_dirty_data_max_percent% of all memory,
+ * capped at zfs_dirty_data_max_max. It can also be overridden with a module
+ * parameter.
+ */
+unsigned long zfs_dirty_data_max = 0;
+unsigned long zfs_dirty_data_max_max = 0;
+int zfs_dirty_data_max_percent = 10;
+int zfs_dirty_data_max_max_percent = 25;
-kmutex_t zfs_write_limit_lock;
+/*
+ * If there is at least this much dirty data, push out a txg.
+ */
+unsigned long zfs_dirty_data_sync = 64 * 1024 * 1024;
-static pgcnt_t old_physmem = 0;
+/*
+ * Once there is this amount of dirty data, the dmu_tx_delay() will kick in
+ * and delay each transaction.
+ * This value should be >= zfs_vdev_async_write_active_max_dirty_percent.
+ */
+int zfs_delay_min_dirty_percent = 60;
+
+/*
+ * This controls how quickly the delay approaches infinity.
+ * Larger values cause it to delay more for a given amount of dirty data.
+ * Therefore larger values will cause there to be less dirty data for a
+ * given throughput.
+ *
+ * For the smoothest delay, this value should be about 1 billion divided
+ * by the maximum number of operations per second. This will smoothly
+ * handle between 10x and 1/10th this number.
+ *
+ * Note: zfs_delay_scale * zfs_dirty_data_max must be < 2^64, due to the
+ * multiply in dmu_tx_delay().
+ */
+unsigned long zfs_delay_scale = 1000 * 1000 * 1000 / 2000;
+
+hrtime_t zfs_throttle_delay = MSEC2NSEC(10);
+hrtime_t zfs_throttle_resolution = MSEC2NSEC(10);
int
dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **ddp)
dp->dp_spa = spa;
dp->dp_meta_rootbp = *bp;
rrw_init(&dp->dp_config_rwlock, B_TRUE);
- dp->dp_write_limit = zfs_write_limit_min;
txg_init(dp, txg);
txg_list_create(&dp->dp_dirty_datasets,
offsetof(dsl_sync_task_t, dst_node));
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("zfs_iput_taskq", 1, minclsyspri,
1, 4, 0);
dp->dp_meta_objset, obj));
}
- if (spa_feature_is_active(dp->dp_spa,
- &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY])) {
+ if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_ASYNC_DESTROY)) {
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_BPTREE_OBJ, sizeof (uint64_t), 1,
&dp->dp_bptree_obj);
goto out;
}
- if (spa_feature_is_active(dp->dp_spa,
- &spa_feature_table[SPA_FEATURE_EMPTY_BPOBJ])) {
+ if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_EMPTY_BPOBJ)) {
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1,
&dp->dp_empty_bpobj);
void
dsl_pool_close(dsl_pool_t *dp)
{
- /* drop our references from dsl_pool_open() */
-
/*
+ * Drop our references from dsl_pool_open().
+ *
* Since we held the origin_snap from "syncing" context (which
* includes pool-opening context), it actually only got a "ref"
* and not a hold, so just drop that here.
return (0);
}
+static void
+dsl_pool_sync_mos(dsl_pool_t *dp, dmu_tx_t *tx)
+{
+ zio_t *zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
+ dmu_objset_sync(dp->dp_meta_objset, zio, tx);
+ VERIFY0(zio_wait(zio));
+ dprintf_bp(&dp->dp_meta_rootbp, "meta objset rootbp is %s", "");
+ spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
+}
+
+static void
+dsl_pool_dirty_delta(dsl_pool_t *dp, int64_t delta)
+{
+ ASSERT(MUTEX_HELD(&dp->dp_lock));
+
+ if (delta < 0)
+ ASSERT3U(-delta, <=, dp->dp_dirty_total);
+
+ dp->dp_dirty_total += delta;
+
+ /*
+ * Note: we signal even when increasing dp_dirty_total.
+ * This ensures forward progress -- each thread wakes the next waiter.
+ */
+ if (dp->dp_dirty_total <= zfs_dirty_data_max)
+ cv_signal(&dp->dp_spaceavail_cv);
+}
+
void
dsl_pool_sync(dsl_pool_t *dp, uint64_t txg)
{
dsl_dir_t *dd;
dsl_dataset_t *ds;
objset_t *mos = dp->dp_meta_objset;
- hrtime_t start, write_time;
- uint64_t data_written;
- int err;
list_t synced_datasets;
list_create(&synced_datasets, sizeof (dsl_dataset_t),
offsetof(dsl_dataset_t, ds_synced_link));
- /*
- * We need to copy dp_space_towrite() before doing
- * dsl_sync_task_sync(), because
- * dsl_dataset_snapshot_reserve_space() will increase
- * dp_space_towrite but not actually write anything.
- */
- data_written = dp->dp_space_towrite[txg & TXG_MASK];
-
tx = dmu_tx_create_assigned(dp, txg);
- dp->dp_read_overhead = 0;
- start = gethrtime();
-
+ /*
+ * Write out all dirty blocks of dirty datasets.
+ */
zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
- while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg))) {
+ while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) {
/*
* We must not sync any non-MOS datasets twice, because
* we may have taken a snapshot of them. However, we
list_insert_tail(&synced_datasets, ds);
dsl_dataset_sync(ds, zio, tx);
}
- DTRACE_PROBE(pool_sync__1setup);
- err = zio_wait(zio);
+ VERIFY0(zio_wait(zio));
- write_time = gethrtime() - start;
- ASSERT(err == 0);
- DTRACE_PROBE(pool_sync__2rootzio);
+ /*
+ * We have written all of the accounted dirty data, so our
+ * dp_space_towrite should now be zero. However, some seldom-used
+ * code paths do not adhere to this (e.g. dbuf_undirty(), also
+ * rounding error in dbuf_write_physdone).
+ * Shore up the accounting of any dirtied space now.
+ */
+ dsl_pool_undirty_space(dp, dp->dp_dirty_pertxg[txg & TXG_MASK], txg);
/*
* After the data blocks have been written (ensured by the zio_wait()
* above), update the user/group space accounting.
*/
- for (ds = list_head(&synced_datasets); ds;
- ds = list_next(&synced_datasets, ds))
+ for (ds = list_head(&synced_datasets); ds != NULL;
+ ds = list_next(&synced_datasets, ds)) {
dmu_objset_do_userquota_updates(ds->ds_objset, tx);
+ }
/*
* Sync the datasets again to push out the changes due to
* about which blocks are part of the snapshot).
*/
zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
- while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg))) {
+ while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) {
ASSERT(list_link_active(&ds->ds_synced_link));
dmu_buf_rele(ds->ds_dbuf, ds);
dsl_dataset_sync(ds, zio, tx);
}
- err = zio_wait(zio);
+ VERIFY0(zio_wait(zio));
/*
* Now that the datasets have been completely synced, we can
* clean up our in-memory structures accumulated while syncing:
*
* - move dead blocks from the pending deadlist to the on-disk deadlist
- * - clean up zil records
* - release hold from dsl_dataset_dirty()
*/
- while ((ds = list_remove_head(&synced_datasets))) {
+ while ((ds = list_remove_head(&synced_datasets)) != NULL) {
ASSERTV(objset_t *os = ds->ds_objset);
bplist_iterate(&ds->ds_pending_deadlist,
deadlist_enqueue_cb, &ds->ds_deadlist, tx);
dmu_buf_rele(ds->ds_dbuf, ds);
}
- start = gethrtime();
- while ((dd = txg_list_remove(&dp->dp_dirty_dirs, txg)))
+ while ((dd = txg_list_remove(&dp->dp_dirty_dirs, txg)) != NULL) {
dsl_dir_sync(dd, tx);
- write_time += gethrtime() - start;
+ }
/*
* The MOS's space is accounted for in the pool/$MOS
dp->dp_mos_uncompressed_delta = 0;
}
- start = gethrtime();
if (list_head(&mos->os_dirty_dnodes[txg & TXG_MASK]) != NULL ||
list_head(&mos->os_free_dnodes[txg & TXG_MASK]) != NULL) {
- zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
- dmu_objset_sync(mos, zio, tx);
- err = zio_wait(zio);
- ASSERT(err == 0);
- dprintf_bp(&dp->dp_meta_rootbp, "meta objset rootbp is %s", "");
- spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
+ dsl_pool_sync_mos(dp, tx);
}
- write_time += gethrtime() - start;
- DTRACE_PROBE2(pool_sync__4io, hrtime_t, write_time,
- hrtime_t, dp->dp_read_overhead);
- write_time -= dp->dp_read_overhead;
/*
* If we modify a dataset in the same txg that we want to destroy it,
* The MOS data dirtied by the sync_tasks will be synced on the next
* pass.
*/
- DTRACE_PROBE(pool_sync__3task);
if (!txg_list_empty(&dp->dp_sync_tasks, txg)) {
dsl_sync_task_t *dst;
/*
* No more sync tasks should have been added while we
* were syncing.
*/
- ASSERT(spa_sync_pass(dp->dp_spa) == 1);
- while ((dst = txg_list_remove(&dp->dp_sync_tasks, txg)))
+ ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1);
+ while ((dst = txg_list_remove(&dp->dp_sync_tasks, txg)) != NULL)
dsl_sync_task_sync(dst, tx);
}
dmu_tx_commit(tx);
- dp->dp_space_towrite[txg & TXG_MASK] = 0;
- ASSERT(dp->dp_tempreserved[txg & TXG_MASK] == 0);
-
- /*
- * If the write limit max has not been explicitly set, set it
- * to a fraction of available physical memory (default 1/8th).
- * Note that we must inflate the limit because the spa
- * inflates write sizes to account for data replication.
- * Check this each sync phase to catch changing memory size.
- */
- if (physmem != old_physmem && zfs_write_limit_shift) {
- mutex_enter(&zfs_write_limit_lock);
- old_physmem = physmem;
- zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
- zfs_write_limit_inflated = MAX(zfs_write_limit_min,
- spa_get_asize(dp->dp_spa, zfs_write_limit_max));
- mutex_exit(&zfs_write_limit_lock);
- }
-
- /*
- * Attempt to keep the sync time consistent by adjusting the
- * amount of write traffic allowed into each transaction group.
- * Weight the throughput calculation towards the current value:
- * thru = 3/4 old_thru + 1/4 new_thru
- *
- * Note: write_time is in nanosecs, so write_time/MICROSEC
- * yields millisecs
- */
- ASSERT(zfs_write_limit_min > 0);
- if (data_written > zfs_write_limit_min / 8 && write_time > MICROSEC) {
- uint64_t throughput = data_written / (write_time / MICROSEC);
-
- if (dp->dp_throughput)
- dp->dp_throughput = throughput / 4 +
- 3 * dp->dp_throughput / 4;
- else
- dp->dp_throughput = throughput;
- dp->dp_write_limit = MIN(zfs_write_limit_inflated,
- MAX(zfs_write_limit_min,
- dp->dp_throughput * zfs_txg_synctime_ms));
- }
+ DTRACE_PROBE2(dsl_pool_sync__done, dsl_pool_t *dp, dp, uint64_t, txg);
}
void
dsl_pool_sync_done(dsl_pool_t *dp, uint64_t txg)
{
zilog_t *zilog;
- dsl_dataset_t *ds;
while ((zilog = txg_list_remove(&dp->dp_dirty_zilogs, txg))) {
- ds = dmu_objset_ds(zilog->zl_os);
+ dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os);
zil_clean(zilog, txg);
ASSERT(!dmu_objset_is_dirty(zilog->zl_os, txg));
dmu_buf_rele(ds->ds_dbuf, zilog);
return (space - resv);
}
-int
-dsl_pool_tempreserve_space(dsl_pool_t *dp, uint64_t space, dmu_tx_t *tx)
+boolean_t
+dsl_pool_need_dirty_delay(dsl_pool_t *dp)
{
- uint64_t reserved = 0;
- uint64_t write_limit = (zfs_write_limit_override ?
- zfs_write_limit_override : dp->dp_write_limit);
-
- if (zfs_no_write_throttle) {
- atomic_add_64(&dp->dp_tempreserved[tx->tx_txg & TXG_MASK],
- space);
- return (0);
- }
-
- /*
- * Check to see if we have exceeded the maximum allowed IO for
- * this transaction group. We can do this without locks since
- * a little slop here is ok. Note that we do the reserved check
- * with only half the requested reserve: this is because the
- * reserve requests are worst-case, and we really don't want to
- * throttle based off of worst-case estimates.
- */
- if (write_limit > 0) {
- reserved = dp->dp_space_towrite[tx->tx_txg & TXG_MASK]
- + dp->dp_tempreserved[tx->tx_txg & TXG_MASK] / 2;
-
- if (reserved && reserved > write_limit) {
- DMU_TX_STAT_BUMP(dmu_tx_write_limit);
- return (ERESTART);
- }
- }
-
- atomic_add_64(&dp->dp_tempreserved[tx->tx_txg & TXG_MASK], space);
-
- /*
- * If this transaction group is over 7/8ths capacity, delay
- * the caller 1 clock tick. This will slow down the "fill"
- * rate until the sync process can catch up with us.
- */
- if (reserved && reserved > (write_limit - (write_limit >> 3)))
- txg_delay(dp, tx->tx_txg, 1);
+ uint64_t delay_min_bytes =
+ zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
+ boolean_t rv;
- return (0);
+ mutex_enter(&dp->dp_lock);
+ if (dp->dp_dirty_total > zfs_dirty_data_sync)
+ txg_kick(dp);
+ rv = (dp->dp_dirty_total > delay_min_bytes);
+ mutex_exit(&dp->dp_lock);
+ return (rv);
}
void
-dsl_pool_tempreserve_clear(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
+dsl_pool_dirty_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
{
- ASSERT(dp->dp_tempreserved[tx->tx_txg & TXG_MASK] >= space);
- atomic_add_64(&dp->dp_tempreserved[tx->tx_txg & TXG_MASK], -space);
+ if (space > 0) {
+ mutex_enter(&dp->dp_lock);
+ dp->dp_dirty_pertxg[tx->tx_txg & TXG_MASK] += space;
+ dsl_pool_dirty_delta(dp, space);
+ mutex_exit(&dp->dp_lock);
+ }
}
void
-dsl_pool_memory_pressure(dsl_pool_t *dp)
+dsl_pool_undirty_space(dsl_pool_t *dp, int64_t space, uint64_t txg)
{
- uint64_t space_inuse = 0;
- int i;
-
- if (dp->dp_write_limit == zfs_write_limit_min)
+ ASSERT3S(space, >=, 0);
+ if (space == 0)
return;
- for (i = 0; i < TXG_SIZE; i++) {
- space_inuse += dp->dp_space_towrite[i];
- space_inuse += dp->dp_tempreserved[i];
- }
- dp->dp_write_limit = MAX(zfs_write_limit_min,
- MIN(dp->dp_write_limit, space_inuse / 4));
-}
-
-void
-dsl_pool_willuse_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
-{
- if (space > 0) {
- mutex_enter(&dp->dp_lock);
- dp->dp_space_towrite[tx->tx_txg & TXG_MASK] += space;
- mutex_exit(&dp->dp_lock);
+ mutex_enter(&dp->dp_lock);
+ if (dp->dp_dirty_pertxg[txg & TXG_MASK] < space) {
+ /* XXX writing something we didn't dirty? */
+ space = dp->dp_dirty_pertxg[txg & TXG_MASK];
}
+ ASSERT3U(dp->dp_dirty_pertxg[txg & TXG_MASK], >=, space);
+ dp->dp_dirty_pertxg[txg & TXG_MASK] -= space;
+ ASSERT3U(dp->dp_dirty_total, >=, space);
+ dsl_pool_dirty_delta(dp, -space);
+ mutex_exit(&dp->dp_lock);
}
/* ARGSUSED */
zap_cursor_t zc;
objset_t *mos = dp->dp_meta_objset;
uint64_t zapobj = dp->dp_tmp_userrefs_obj;
+ nvlist_t *holds;
if (zapobj == 0)
return;
ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
+ holds = fnvlist_alloc();
+
for (zap_cursor_init(&zc, mos, zapobj);
zap_cursor_retrieve(&zc, &za) == 0;
zap_cursor_advance(&zc)) {
char *htag;
- uint64_t dsobj;
+ nvlist_t *tags;
htag = strchr(za.za_name, '-');
*htag = '\0';
++htag;
- dsobj = strtonum(za.za_name, NULL);
- dsl_dataset_user_release_tmp(dp, dsobj, htag);
+ if (nvlist_lookup_nvlist(holds, za.za_name, &tags) != 0) {
+ tags = fnvlist_alloc();
+ fnvlist_add_boolean(tags, htag);
+ fnvlist_add_nvlist(holds, za.za_name, tags);
+ fnvlist_free(tags);
+ } else {
+ fnvlist_add_boolean(tags, htag);
+ }
}
+ dsl_dataset_user_release_tmp(dp, holds);
+ fnvlist_free(holds);
zap_cursor_fini(&zc);
}
dsl_pool_user_hold_create_obj(dp, tx);
zapobj = dp->dp_tmp_userrefs_obj;
} else {
- return (ENOENT);
+ return (SET_ERROR(ENOENT));
}
}
EXPORT_SYMBOL(dsl_pool_config_enter);
EXPORT_SYMBOL(dsl_pool_config_exit);
-module_param(zfs_no_write_throttle, int, 0644);
-MODULE_PARM_DESC(zfs_no_write_throttle, "Disable write throttling");
+/* zfs_dirty_data_max_percent only applied at module load in arc_init(). */
+module_param(zfs_dirty_data_max_percent, int, 0444);
+MODULE_PARM_DESC(zfs_dirty_data_max_percent, "percent of ram can be dirty");
-module_param(zfs_write_limit_shift, int, 0444);
-MODULE_PARM_DESC(zfs_write_limit_shift, "log2(fraction of memory) per txg");
+/* zfs_dirty_data_max_max_percent only applied at module load in arc_init(). */
+module_param(zfs_dirty_data_max_max_percent, int, 0444);
+MODULE_PARM_DESC(zfs_dirty_data_max_max_percent,
+ "zfs_dirty_data_max upper bound as % of RAM");
-module_param(zfs_txg_synctime_ms, int, 0644);
-MODULE_PARM_DESC(zfs_txg_synctime_ms, "Target milliseconds between txg sync");
+module_param(zfs_delay_min_dirty_percent, int, 0644);
+MODULE_PARM_DESC(zfs_delay_min_dirty_percent, "transaction delay threshold");
-module_param(zfs_write_limit_min, ulong, 0444);
-MODULE_PARM_DESC(zfs_write_limit_min, "Min txg write limit");
+module_param(zfs_dirty_data_max, ulong, 0644);
+MODULE_PARM_DESC(zfs_dirty_data_max, "determines the dirty space limit");
-module_param(zfs_write_limit_max, ulong, 0444);
-MODULE_PARM_DESC(zfs_write_limit_max, "Max txg write limit");
+/* zfs_dirty_data_max_max only applied at module load in arc_init(). */
+module_param(zfs_dirty_data_max_max, ulong, 0444);
+MODULE_PARM_DESC(zfs_dirty_data_max_max,
+ "zfs_dirty_data_max upper bound in bytes");
-module_param(zfs_write_limit_inflated, ulong, 0444);
-MODULE_PARM_DESC(zfs_write_limit_inflated, "Inflated txg write limit");
+module_param(zfs_dirty_data_sync, ulong, 0644);
+MODULE_PARM_DESC(zfs_dirty_data_sync, "sync txg when this much dirty data");
-module_param(zfs_write_limit_override, ulong, 0444);
-MODULE_PARM_DESC(zfs_write_limit_override, "Override txg write limit");
+module_param(zfs_delay_scale, ulong, 0644);
+MODULE_PARM_DESC(zfs_delay_scale, "how quickly delay approaches infinity");
#endif
projects / mirror_zfs.git / blobdiff