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 38 extern "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 */ 70 struct 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 */ 90 typedef 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