--- /dev/null
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+
+/*
+ * Copyright (c) 2013 by Delphix. All rights reserved.
+ */
+
+#ifndef _SYS_TXG_IMPL_H
+#define _SYS_TXG_IMPL_H
+
+#include <sys/spa.h>
+#include <sys/txg.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * The tx_cpu structure is a per-cpu structure that is used to track
+ * the number of active transaction holds (tc_count). As transactions
+ * are assigned into a transaction group the appropriate tc_count is
+ * incremented to indicate that there are pending changes that have yet
+ * to quiesce. Consumers evenutally call txg_rele_to_sync() to decrement
+ * the tc_count. A transaction group is not considered quiesced until all
+ * tx_cpu structures have reached a tc_count of zero.
+ *
+ * This structure is a per-cpu structure by design. Updates to this structure
+ * are frequent and concurrent. Having a single structure would result in
+ * heavy lock contention so a per-cpu design was implemented. With the fanned
+ * out mutex design, consumers only need to lock the mutex associated with
+ * thread's cpu.
+ *
+ * The tx_cpu contains two locks, the tc_lock and tc_open_lock.
+ * The tc_lock is used to protect all members of the tx_cpu structure with
+ * the exception of the tc_open_lock. This lock should only be held for a
+ * short period of time, typically when updating the value of tc_count.
+ *
+ * The tc_open_lock protects the tx_open_txg member of the tx_state structure.
+ * This lock is used to ensure that transactions are only assigned into
+ * the current open transaction group. In order to move the current open
+ * transaction group to the quiesce phase, the txg_quiesce thread must
+ * grab all tc_open_locks, increment the tx_open_txg, and drop the locks.
+ * The tc_open_lock is held until the transaction is assigned into the
+ * transaction group. Typically, this is a short operation but if throttling
+ * is occuring it may be held for longer periods of time.
+ */
+struct tx_cpu {
+ kmutex_t tc_open_lock; /* protects tx_open_txg */
+ kmutex_t tc_lock; /* protects the rest of this struct */
+ kcondvar_t tc_cv[TXG_SIZE];
+ uint64_t tc_count[TXG_SIZE]; /* tx hold count on each txg */
+ list_t tc_callbacks[TXG_SIZE]; /* commit cb list */
+ char tc_pad[8]; /* pad to fill 3 cache lines */
+};
+
+/*
+ * The tx_state structure maintains the state information about the different
+ * stages of the pool's transcation groups. A per pool tx_state structure
+ * is used to track this information. The tx_state structure also points to
+ * an array of tx_cpu structures (described above). Although the tx_sync_lock
+ * is used to protect the members of this structure, it is not used to
+ * protect the tx_open_txg. Instead a special lock in the tx_cpu structure
+ * is used. Readers of tx_open_txg must grab the per-cpu tc_open_lock.
+ * Any thread wishing to update tx_open_txg must grab the tc_open_lock on
+ * every cpu (see txg_quiesce()).
+ */
+typedef struct tx_state {
+ tx_cpu_t *tx_cpu; /* protects access to tx_open_txg */
+ kmutex_t tx_sync_lock; /* protects the rest of this struct */
+
+ uint64_t tx_open_txg; /* currently open txg id */
+ uint64_t tx_quiesced_txg; /* quiesced txg waiting for sync */
+ uint64_t tx_syncing_txg; /* currently syncing txg id */
+ uint64_t tx_synced_txg; /* last synced txg id */
+
+ hrtime_t tx_open_time; /* start time of tx_open_txg */
+
+ uint64_t tx_sync_txg_waiting; /* txg we're waiting to sync */
+ uint64_t tx_quiesce_txg_waiting; /* txg we're waiting to open */
+
+ kcondvar_t tx_sync_more_cv;
+ kcondvar_t tx_sync_done_cv;
+ kcondvar_t tx_quiesce_more_cv;
+ kcondvar_t tx_quiesce_done_cv;
+ kcondvar_t tx_timeout_cv;
+ kcondvar_t tx_exit_cv; /* wait for all threads to exit */
+
+ uint8_t tx_threads; /* number of threads */
+ uint8_t tx_exiting; /* set when we're exiting */
+
+ kthread_t *tx_sync_thread;
+ kthread_t *tx_quiesce_thread;
+
+ taskq_t *tx_commit_cb_taskq; /* commit callback taskq */
+} tx_state_t;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SYS_TXG_IMPL_H */
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