*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Portions Copyright 2011 Martin Matuska
+ * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
#include <sys/txg_impl.h>
#include <sys/dmu_impl.h>
+#include <sys/spa_impl.h>
#include <sys/dmu_tx.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_scan.h>
#include <sys/callb.h>
+#include <sys/trace_txg.h>
/*
- * Pool-wide transaction groups.
+ * ZFS Transaction Groups
+ * ----------------------
+ *
+ * ZFS transaction groups are, as the name implies, groups of transactions
+ * that act on persistent state. ZFS asserts consistency at the granularity of
+ * these transaction groups. Each successive transaction group (txg) is
+ * assigned a 64-bit consecutive identifier. There are three active
+ * transaction group states: open, quiescing, or syncing. At any given time,
+ * there may be an active txg associated with each state; each active txg may
+ * either be processing, or blocked waiting to enter the next state. There may
+ * be up to three active txgs, and there is always a txg in the open state
+ * (though it may be blocked waiting to enter the quiescing state). In broad
+ * strokes, transactions -- operations that change in-memory structures -- are
+ * accepted into the txg in the open state, and are completed while the txg is
+ * in the open or quiescing states. The accumulated changes are written to
+ * disk in the syncing state.
+ *
+ * Open
+ *
+ * When a new txg becomes active, it first enters the open state. New
+ * transactions -- updates to in-memory structures -- are assigned to the
+ * currently open txg. There is always a txg in the open state so that ZFS can
+ * accept new changes (though the txg may refuse new changes if it has hit
+ * some limit). ZFS advances the open txg to the next state for a variety of
+ * reasons such as it hitting a time or size threshold, or the execution of an
+ * administrative action that must be completed in the syncing state.
+ *
+ * Quiescing
+ *
+ * After a txg exits the open state, it enters the quiescing state. The
+ * quiescing state is intended to provide a buffer between accepting new
+ * transactions in the open state and writing them out to stable storage in
+ * the syncing state. While quiescing, transactions can continue their
+ * operation without delaying either of the other states. Typically, a txg is
+ * in the quiescing state very briefly since the operations are bounded by
+ * software latencies rather than, say, slower I/O latencies. After all
+ * transactions complete, the txg is ready to enter the next state.
+ *
+ * Syncing
+ *
+ * In the syncing state, the in-memory state built up during the open and (to
+ * a lesser degree) the quiescing states is written to stable storage. The
+ * process of writing out modified data can, in turn modify more data. For
+ * example when we write new blocks, we need to allocate space for them; those
+ * allocations modify metadata (space maps)... which themselves must be
+ * written to stable storage. During the sync state, ZFS iterates, writing out
+ * data until it converges and all in-memory changes have been written out.
+ * The first such pass is the largest as it encompasses all the modified user
+ * data (as opposed to filesystem metadata). Subsequent passes typically have
+ * far less data to write as they consist exclusively of filesystem metadata.
+ *
+ * To ensure convergence, after a certain number of passes ZFS begins
+ * overwriting locations on stable storage that had been allocated earlier in
+ * the syncing state (and subsequently freed). ZFS usually allocates new
+ * blocks to optimize for large, continuous, writes. For the syncing state to
+ * converge however it must complete a pass where no new blocks are allocated
+ * since each allocation requires a modification of persistent metadata.
+ * Further, to hasten convergence, after a prescribed number of passes, ZFS
+ * also defers frees, and stops compressing.
+ *
+ * In addition to writing out user data, we must also execute synctasks during
+ * the syncing context. A synctask is the mechanism by which some
+ * administrative activities work such as creating and destroying snapshots or
+ * datasets. Note that when a synctask is initiated it enters the open txg,
+ * and ZFS then pushes that txg as quickly as possible to completion of the
+ * syncing state in order to reduce the latency of the administrative
+ * activity. To complete the syncing state, ZFS writes out a new uberblock,
+ * the root of the tree of blocks that comprise all state stored on the ZFS
+ * pool. Finally, if there is a quiesced txg waiting, we signal that it can
+ * now transition to the syncing state.
*/
static void txg_sync_thread(dsl_pool_t *dp);
int i;
mutex_init(&tx->tx_cpu[c].tc_lock, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&tx->tx_cpu[c].tc_open_lock, NULL, MUTEX_DEFAULT,
+ NULL);
for (i = 0; i < TXG_SIZE; i++) {
cv_init(&tx->tx_cpu[c].tc_cv[i], NULL, CV_DEFAULT,
NULL);
for (c = 0; c < max_ncpus; c++) {
int i;
+ mutex_destroy(&tx->tx_cpu[c].tc_open_lock);
mutex_destroy(&tx->tx_cpu[c].tc_lock);
for (i = 0; i < TXG_SIZE; i++) {
cv_destroy(&tx->tx_cpu[c].tc_cv[i]);
}
static void
-txg_thread_wait(tx_state_t *tx, callb_cpr_t *cpr, kcondvar_t *cv, uint64_t time)
+txg_thread_wait(tx_state_t *tx, callb_cpr_t *cpr, kcondvar_t *cv, clock_t time)
{
CALLB_CPR_SAFE_BEGIN(cpr);
txg_hold_open(dsl_pool_t *dp, txg_handle_t *th)
{
tx_state_t *tx = &dp->dp_tx;
- tx_cpu_t *tc = &tx->tx_cpu[CPU_SEQID];
+ tx_cpu_t *tc;
uint64_t txg;
- mutex_enter(&tc->tc_lock);
+ /*
+ * It appears the processor id is simply used as a "random"
+ * number to index into the array, and there isn't any other
+ * significance to the chosen tx_cpu. Because.. Why not use
+ * the current cpu to index into the array?
+ */
+ kpreempt_disable();
+ tc = &tx->tx_cpu[CPU_SEQID];
+ kpreempt_enable();
+ mutex_enter(&tc->tc_open_lock);
txg = tx->tx_open_txg;
+
+ mutex_enter(&tc->tc_lock);
tc->tc_count[txg & TXG_MASK]++;
+ mutex_exit(&tc->tc_lock);
th->th_cpu = tc;
th->th_txg = txg;
{
tx_cpu_t *tc = th->th_cpu;
- mutex_exit(&tc->tc_lock);
+ ASSERT(!MUTEX_HELD(&tc->tc_lock));
+ mutex_exit(&tc->tc_open_lock);
}
void
th->th_cpu = NULL; /* defensive */
}
+/*
+ * Blocks until all transactions in the group are committed.
+ *
+ * On return, the transaction group has reached a stable state in which it can
+ * then be passed off to the syncing context.
+ */
static void
txg_quiesce(dsl_pool_t *dp, uint64_t txg)
{
int c;
/*
- * Grab all tx_cpu locks so nobody else can get into this txg.
+ * Grab all tc_open_locks so nobody else can get into this txg.
*/
for (c = 0; c < max_ncpus; c++)
- mutex_enter(&tx->tx_cpu[c].tc_lock);
+ mutex_enter(&tx->tx_cpu[c].tc_open_lock);
ASSERT(txg == tx->tx_open_txg);
tx->tx_open_txg++;
+ tx->tx_open_time = gethrtime();
+
+ spa_txg_history_set(dp->dp_spa, txg, TXG_STATE_OPEN, tx->tx_open_time);
+ spa_txg_history_add(dp->dp_spa, tx->tx_open_txg, tx->tx_open_time);
+
+ DTRACE_PROBE2(txg__quiescing, dsl_pool_t *, dp, uint64_t, txg);
+ DTRACE_PROBE2(txg__opened, dsl_pool_t *, dp, uint64_t, tx->tx_open_txg);
/*
* Now that we've incremented tx_open_txg, we can let threads
* enter the next transaction group.
*/
for (c = 0; c < max_ncpus; c++)
- mutex_exit(&tx->tx_cpu[c].tc_lock);
+ mutex_exit(&tx->tx_cpu[c].tc_open_lock);
/*
* Quiesce the transaction group by waiting for everyone to txg_exit().
cv_wait(&tc->tc_cv[g], &tc->tc_lock);
mutex_exit(&tc->tc_lock);
}
+
+ spa_txg_history_set(dp->dp_spa, txg, TXG_STATE_QUIESCED, gethrtime());
}
static void
/*
* Dispatch the commit callbacks registered on this txg to worker threads.
+ *
+ * If no callbacks are registered for a given TXG, nothing happens.
+ * This function creates a taskq for the associated pool, if needed.
*/
static void
txg_dispatch_callbacks(dsl_pool_t *dp, uint64_t txg)
for (c = 0; c < max_ncpus; c++) {
tx_cpu_t *tc = &tx->tx_cpu[c];
- /* No need to lock tx_cpu_t at this point */
+ /*
+ * No need to lock tx_cpu_t at this point, since this can
+ * only be called once a txg has been synced.
+ */
int g = txg & TXG_MASK;
spa_t *spa = dp->dp_spa;
tx_state_t *tx = &dp->dp_tx;
callb_cpr_t cpr;
- uint64_t start, delta;
-
-#ifdef _KERNEL
- /*
- * Disable the normal reclaim path for the txg_sync thread. This
- * ensures the thread will never enter dmu_tx_assign() which can
- * otherwise occur due to direct reclaim. If this is allowed to
- * happen the system can deadlock. Direct reclaim call path:
- *
- * ->shrink_icache_memory->prune_icache->dispose_list->
- * clear_inode->zpl_clear_inode->zfs_inactive->dmu_tx_assign
- */
- current->flags |= PF_MEMALLOC;
-#endif /* _KERNEL */
+ vdev_stat_t *vs1, *vs2;
+ clock_t start, delta;
+ (void) spl_fstrans_mark();
txg_thread_enter(tx, &cpr);
+ vs1 = kmem_alloc(sizeof (vdev_stat_t), KM_SLEEP);
+ vs2 = kmem_alloc(sizeof (vdev_stat_t), KM_SLEEP);
+
start = delta = 0;
for (;;) {
- uint64_t timer, timeout = zfs_txg_timeout * hz;
+ clock_t timer, timeout;
uint64_t txg;
+ uint64_t ndirty;
+
+ timeout = zfs_txg_timeout * hz;
/*
* We sync when we're scanning, there's someone waiting
while (!dsl_scan_active(dp->dp_scan) &&
!tx->tx_exiting && timer > 0 &&
tx->tx_synced_txg >= tx->tx_sync_txg_waiting &&
- tx->tx_quiesced_txg == 0) {
+ tx->tx_quiesced_txg == 0 &&
+ dp->dp_dirty_total < zfs_dirty_data_sync) {
dprintf("waiting; tx_synced=%llu waiting=%llu dp=%p\n",
tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
txg_thread_wait(tx, &cpr, &tx->tx_sync_more_cv, timer);
txg_thread_wait(tx, &cpr, &tx->tx_quiesce_done_cv, 0);
}
- if (tx->tx_exiting)
+ if (tx->tx_exiting) {
+ kmem_free(vs2, sizeof (vdev_stat_t));
+ kmem_free(vs1, sizeof (vdev_stat_t));
txg_thread_exit(tx, &cpr, &tx->tx_sync_thread);
+ }
+
+ spa_config_enter(spa, SCL_ALL, FTAG, RW_READER);
+ vdev_get_stats(spa->spa_root_vdev, vs1);
+ spa_config_exit(spa, SCL_ALL, FTAG);
/*
* Consume the quiesced txg which has been handed off to
txg = tx->tx_quiesced_txg;
tx->tx_quiesced_txg = 0;
tx->tx_syncing_txg = txg;
+ DTRACE_PROBE2(txg__syncing, dsl_pool_t *, dp, uint64_t, txg);
cv_broadcast(&tx->tx_quiesce_more_cv);
dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
mutex_exit(&tx->tx_sync_lock);
+ spa_txg_history_set(spa, txg, TXG_STATE_WAIT_FOR_SYNC,
+ gethrtime());
+ ndirty = dp->dp_dirty_pertxg[txg & TXG_MASK];
+
start = ddi_get_lbolt();
spa_sync(spa, txg);
delta = ddi_get_lbolt() - start;
mutex_enter(&tx->tx_sync_lock);
tx->tx_synced_txg = txg;
tx->tx_syncing_txg = 0;
+ DTRACE_PROBE2(txg__synced, dsl_pool_t *, dp, uint64_t, txg);
cv_broadcast(&tx->tx_sync_done_cv);
/*
* Dispatch commit callbacks to worker threads.
*/
txg_dispatch_callbacks(dp, txg);
+
+ spa_config_enter(spa, SCL_ALL, FTAG, RW_READER);
+ vdev_get_stats(spa->spa_root_vdev, vs2);
+ spa_config_exit(spa, SCL_ALL, FTAG);
+ spa_txg_history_set_io(spa, txg,
+ vs2->vs_bytes[ZIO_TYPE_READ]-vs1->vs_bytes[ZIO_TYPE_READ],
+ vs2->vs_bytes[ZIO_TYPE_WRITE]-vs1->vs_bytes[ZIO_TYPE_WRITE],
+ vs2->vs_ops[ZIO_TYPE_READ]-vs1->vs_ops[ZIO_TYPE_READ],
+ vs2->vs_ops[ZIO_TYPE_WRITE]-vs1->vs_ops[ZIO_TYPE_WRITE],
+ ndirty);
+ spa_txg_history_set(spa, txg, TXG_STATE_SYNCED, gethrtime());
}
}
*/
dprintf("quiesce done, handing off txg %llu\n", txg);
tx->tx_quiesced_txg = txg;
+ DTRACE_PROBE2(txg__quiesced, dsl_pool_t *, dp, uint64_t, txg);
cv_broadcast(&tx->tx_sync_more_cv);
cv_broadcast(&tx->tx_quiesce_done_cv);
}
}
/*
- * Delay this thread by 'ticks' if we are still in the open transaction
- * group and there is already a waiting txg quiesing or quiesced. Abort
- * the delay if this txg stalls or enters the quiesing state.
+ * Delay this thread by delay nanoseconds if we are still in the open
+ * transaction group and there is already a waiting txg quiesing or quiesced.
+ * Abort the delay if this txg stalls or enters the quiesing state.
*/
void
-txg_delay(dsl_pool_t *dp, uint64_t txg, int ticks)
+txg_delay(dsl_pool_t *dp, uint64_t txg, hrtime_t delay, hrtime_t resolution)
{
tx_state_t *tx = &dp->dp_tx;
- int timeout = ddi_get_lbolt() + ticks;
+ hrtime_t start = gethrtime();
- /* don't delay if this txg could transition to quiesing immediately */
+ /* don't delay if this txg could transition to quiescing immediately */
if (tx->tx_open_txg > txg ||
tx->tx_syncing_txg == txg-1 || tx->tx_synced_txg == txg-1)
return;
return;
}
- while (ddi_get_lbolt() < timeout &&
- tx->tx_syncing_txg < txg-1 && !txg_stalled(dp))
- (void) cv_timedwait(&tx->tx_quiesce_more_cv, &tx->tx_sync_lock,
- timeout);
+ while (gethrtime() - start < delay &&
+ tx->tx_syncing_txg < txg-1 && !txg_stalled(dp)) {
+ (void) cv_timedwait_hires(&tx->tx_quiesce_more_cv,
+ &tx->tx_sync_lock, delay, resolution, 0);
+ }
+
+ DMU_TX_STAT_BUMP(dmu_tx_delay);
mutex_exit(&tx->tx_sync_lock);
}
{
tx_state_t *tx = &dp->dp_tx;
+ ASSERT(!dsl_pool_config_held(dp));
+
mutex_enter(&tx->tx_sync_lock);
ASSERT(tx->tx_threads == 2);
if (txg == 0)
{
tx_state_t *tx = &dp->dp_tx;
+ ASSERT(!dsl_pool_config_held(dp));
+
mutex_enter(&tx->tx_sync_lock);
ASSERT(tx->tx_threads == 2);
if (txg == 0)
mutex_exit(&tx->tx_sync_lock);
}
+/*
+ * If there isn't a txg syncing or in the pipeline, push another txg through
+ * the pipeline by queiscing the open txg.
+ */
+void
+txg_kick(dsl_pool_t *dp)
+{
+ tx_state_t *tx = &dp->dp_tx;
+
+ ASSERT(!dsl_pool_config_held(dp));
+
+ mutex_enter(&tx->tx_sync_lock);
+ if (tx->tx_syncing_txg == 0 &&
+ tx->tx_quiesce_txg_waiting <= tx->tx_open_txg &&
+ tx->tx_sync_txg_waiting <= tx->tx_synced_txg &&
+ tx->tx_quiesced_txg <= tx->tx_synced_txg) {
+ tx->tx_quiesce_txg_waiting = tx->tx_open_txg + 1;
+ cv_broadcast(&tx->tx_quiesce_more_cv);
+ }
+ mutex_exit(&tx->tx_sync_lock);
+}
+
boolean_t
txg_stalled(dsl_pool_t *dp)
{
mutex_destroy(&tl->tl_lock);
}
-int
+boolean_t
txg_list_empty(txg_list_t *tl, uint64_t txg)
{
return (tl->tl_head[txg & TXG_MASK] == NULL);
}
/*
- * Add an entry to the list.
- * Returns 0 if it's a new entry, 1 if it's already there.
+ * Returns true if all txg lists are empty.
+ *
+ * Warning: this is inherently racy (an item could be added immediately
+ * after this function returns). We don't bother with the lock because
+ * it wouldn't change the semantics.
+ */
+boolean_t
+txg_all_lists_empty(txg_list_t *tl)
+{
+ int i;
+
+ for (i = 0; i < TXG_SIZE; i++) {
+ if (!txg_list_empty(tl, i)) {
+ return (B_FALSE);
+ }
+ }
+ return (B_TRUE);
+}
+
+/*
+ * Add an entry to the list (unless it's already on the list).
+ * Returns B_TRUE if it was actually added.
*/
-int
+boolean_t
txg_list_add(txg_list_t *tl, void *p, uint64_t txg)
{
int t = txg & TXG_MASK;
txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
- int already_on_list;
+ boolean_t add;
mutex_enter(&tl->tl_lock);
- already_on_list = tn->tn_member[t];
- if (!already_on_list) {
+ add = (tn->tn_member[t] == 0);
+ if (add) {
tn->tn_member[t] = 1;
tn->tn_next[t] = tl->tl_head[t];
tl->tl_head[t] = tn;
}
mutex_exit(&tl->tl_lock);
- return (already_on_list);
+ return (add);
}
/*
- * Add an entry to the end of the list (walks list to find end).
- * Returns 0 if it's a new entry, 1 if it's already there.
+ * Add an entry to the end of the list, unless it's already on the list.
+ * (walks list to find end)
+ * Returns B_TRUE if it was actually added.
*/
-int
+boolean_t
txg_list_add_tail(txg_list_t *tl, void *p, uint64_t txg)
{
int t = txg & TXG_MASK;
txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
- int already_on_list;
+ boolean_t add;
mutex_enter(&tl->tl_lock);
- already_on_list = tn->tn_member[t];
- if (!already_on_list) {
+ add = (tn->tn_member[t] == 0);
+ if (add) {
txg_node_t **tp;
for (tp = &tl->tl_head[t]; *tp != NULL; tp = &(*tp)->tn_next[t])
}
mutex_exit(&tl->tl_lock);
- return (already_on_list);
+ return (add);
}
/*
return (NULL);
}
-int
+boolean_t
txg_list_member(txg_list_t *tl, void *p, uint64_t txg)
{
int t = txg & TXG_MASK;
txg_node_t *tn = (txg_node_t *)((char *)p + tl->tl_offset);
- return (tn->tn_member[t]);
+ return (tn->tn_member[t] != 0);
}
/*
EXPORT_SYMBOL(txg_wait_callbacks);
EXPORT_SYMBOL(txg_stalled);
EXPORT_SYMBOL(txg_sync_waiting);
+
+module_param(zfs_txg_timeout, int, 0644);
+MODULE_PARM_DESC(zfs_txg_timeout, "Max seconds worth of delta per txg");
#endif
projects / mirror_zfs-debian.git / blobdiff