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