1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27/*
28 * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
29 */
30
31#ifndef _SYS_TXG_IMPL_H
32#define	_SYS_TXG_IMPL_H
33
34#include <sys/spa.h>
35#include <sys/txg.h>
36
37#ifdef	__cplusplus
38extern "C" {
39#endif
40
41/*
42 * The tx_cpu structure is a per-cpu structure that is used to track
43 * the number of active transaction holds (tc_count). As transactions
44 * are assigned into a transaction group the appropriate tc_count is
45 * incremented to indicate that there are pending changes that have yet
46 * to quiesce. Consumers evenutally call txg_rele_to_sync() to decrement
47 * the tc_count. A transaction group is not considered quiesced until all
48 * tx_cpu structures have reached a tc_count of zero.
49 *
50 * This structure is a per-cpu structure by design. Updates to this structure
51 * are frequent and concurrent. Having a single structure would result in
52 * heavy lock contention so a per-cpu design was implemented. With the fanned
53 * out mutex design, consumers only need to lock the mutex associated with
54 * thread's cpu.
55 *
56 * The tx_cpu contains two locks, the tc_lock and tc_open_lock.
57 * The tc_lock is used to protect all members of the tx_cpu structure with
58 * the exception of the tc_open_lock. This lock should only be held for a
59 * short period of time, typically when updating the value of tc_count.
60 *
61 * The tc_open_lock protects the tx_open_txg member of the tx_state structure.
62 * This lock is used to ensure that transactions are only assigned into
63 * the current open transaction group. In order to move the current open
64 * transaction group to the quiesce phase, the txg_quiesce thread must
65 * grab all tc_open_locks, increment the tx_open_txg, and drop the locks.
66 * The tc_open_lock is held until the transaction is assigned into the
67 * transaction group. Typically, this is a short operation but if throttling
68 * is occuring it may be held for longer periods of time.
69 */
70struct tx_cpu {
71	kmutex_t	tc_open_lock;	/* protects tx_open_txg */
72	kmutex_t	tc_lock;	/* protects the rest of this struct */
73	kcondvar_t	tc_cv[TXG_SIZE];
74	uint64_t	tc_count[TXG_SIZE];	/* tx hold count on each txg */
75	list_t		tc_callbacks[TXG_SIZE]; /* commit cb list */
76	char		tc_pad[8];		/* pad to fill 3 cache lines */
77};
78
79/*
80 * The tx_state structure maintains the state information about the different
81 * stages of the pool's transcation groups. A per pool tx_state structure
82 * is used to track this information. The tx_state structure also points to
83 * an array of tx_cpu structures (described above). Although the tx_sync_lock
84 * is used to protect the members of this structure, it is not used to
85 * protect the tx_open_txg. Instead a special lock in the tx_cpu structure
86 * is used. Readers of tx_open_txg must grab the per-cpu tc_open_lock.
87 * Any thread wishing to update tx_open_txg must grab the tc_open_lock on
88 * every cpu (see txg_quiesce()).
89 */
90typedef struct tx_state {
91	tx_cpu_t	*tx_cpu;	/* protects access to tx_open_txg */
92	kmutex_t	tx_sync_lock;	/* protects the rest of this struct */
93
94	uint64_t	tx_open_txg;	/* currently open txg id */
95	uint64_t	tx_quiescing_txg; /* currently quiescing txg id */
96	uint64_t	tx_quiesced_txg; /* quiesced txg waiting for sync */
97	uint64_t	tx_syncing_txg;	/* currently syncing txg id */
98	uint64_t	tx_synced_txg;	/* last synced txg id */
99
100	hrtime_t	tx_open_time;	/* start time of tx_open_txg */
101
102	uint64_t	tx_sync_txg_waiting; /* txg we're waiting to sync */
103	uint64_t	tx_quiesce_txg_waiting; /* txg we're waiting to open */
104
105	kcondvar_t	tx_sync_more_cv;
106	kcondvar_t	tx_sync_done_cv;
107	kcondvar_t	tx_quiesce_more_cv;
108	kcondvar_t	tx_quiesce_done_cv;
109	kcondvar_t	tx_timeout_cv;
110	kcondvar_t	tx_exit_cv;	/* wait for all threads to exit */
111
112	uint8_t		tx_threads;	/* number of threads */
113	uint8_t		tx_exiting;	/* set when we're exiting */
114
115	kthread_t	*tx_sync_thread;
116	kthread_t	*tx_quiesce_thread;
117
118	taskq_t		*tx_commit_cb_taskq; /* commit callback taskq */
119} tx_state_t;
120
121#ifdef	__cplusplus
122}
123#endif
124
125#endif	/* _SYS_TXG_IMPL_H */
126