diff options
Diffstat (limited to 'module/zfs/dsl_pool.c')
| -rw-r--r-- | module/zfs/dsl_pool.c | 360 |
1 files changed, 183 insertions, 177 deletions
diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c index e7127c535..eed4bd497 100644 --- a/module/zfs/dsl_pool.c +++ b/module/zfs/dsl_pool.c @@ -46,18 +46,85 @@ #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. + */ + +/* + * 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; -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; +/* + * If there is at least this much dirty data, push out a txg. + */ +unsigned long zfs_dirty_data_sync = 64 * 1024 * 1024; -kmutex_t zfs_write_limit_lock; +/* + * 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; -static pgcnt_t old_physmem = 0; +/* + * 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); @@ -87,7 +154,6 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg) 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, @@ -100,6 +166,7 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg) 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); @@ -214,9 +281,9 @@ out: 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. @@ -346,6 +413,34 @@ deadlist_enqueue_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx) 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) { @@ -354,29 +449,18 @@ 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 @@ -386,20 +470,25 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) 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 @@ -409,12 +498,12 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) * 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 @@ -423,7 +512,7 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) * - move dead blocks from the pending deadlist to the on-disk deadlist * - 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); @@ -431,10 +520,9 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) 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 @@ -452,20 +540,10 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) 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, @@ -476,72 +554,29 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg) * 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 while dp_throughput is expressed in - * bytes per millisecond. - */ - ASSERT(zfs_write_limit_min > 0); - if (data_written > zfs_write_limit_min / 8 && - write_time > MSEC2NSEC(1)) { - uint64_t throughput = data_written / NSEC2MSEC(write_time); - - 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); @@ -583,84 +618,49 @@ dsl_pool_adjustedsize(dsl_pool_t *dp, boolean_t netfree) 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; + uint64_t delay_min_bytes = + zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100; + boolean_t rv; - if (reserved && reserved > write_limit) { - DMU_TX_STAT_BUMP(dmu_tx_write_limit); - return (SET_ERROR(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, zfs_throttle_delay, - zfs_throttle_resolution); - } - - 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 */ @@ -1049,24 +1049,30 @@ dsl_pool_config_held(dsl_pool_t *dp) 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 time 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 time 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 time 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 |