126 lines
4.8 KiB
C
126 lines
4.8 KiB
C
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/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* Copyright (c) 2013, 2017 by Delphix. All rights reserved.
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*/
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#ifndef _SYS_TXG_IMPL_H
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#define _SYS_TXG_IMPL_H
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#include <sys/spa.h>
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#include <sys/txg.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* The tx_cpu structure is a per-cpu structure that is used to track
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* the number of active transaction holds (tc_count). As transactions
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* are assigned into a transaction group the appropriate tc_count is
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* incremented to indicate that there are pending changes that have yet
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* to quiesce. Consumers eventually call txg_rele_to_sync() to decrement
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* the tc_count. A transaction group is not considered quiesced until all
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* tx_cpu structures have reached a tc_count of zero.
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*
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* This structure is a per-cpu structure by design. Updates to this structure
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* are frequent and concurrent. Having a single structure would result in
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* heavy lock contention so a per-cpu design was implemented. With the fanned
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* out mutex design, consumers only need to lock the mutex associated with
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* thread's cpu.
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*
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* The tx_cpu contains two locks, the tc_lock and tc_open_lock.
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* The tc_lock is used to protect all members of the tx_cpu structure with
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* the exception of the tc_open_lock. This lock should only be held for a
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* short period of time, typically when updating the value of tc_count.
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*
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* The tc_open_lock protects the tx_open_txg member of the tx_state structure.
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* This lock is used to ensure that transactions are only assigned into
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* the current open transaction group. In order to move the current open
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* transaction group to the quiesce phase, the txg_quiesce thread must
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* grab all tc_open_locks, increment the tx_open_txg, and drop the locks.
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* The tc_open_lock is held until the transaction is assigned into the
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* transaction group. Typically, this is a short operation but if throttling
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* is occurring it may be held for longer periods of time.
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*/
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struct tx_cpu {
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kmutex_t tc_open_lock; /* protects tx_open_txg */
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kmutex_t tc_lock; /* protects the rest of this struct */
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kcondvar_t tc_cv[TXG_SIZE];
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uint64_t tc_count[TXG_SIZE]; /* tx hold count on each txg */
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list_t tc_callbacks[TXG_SIZE]; /* commit cb list */
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char tc_pad[8]; /* pad to fill 3 cache lines */
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};
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/*
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* The tx_state structure maintains the state information about the different
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* stages of the pool's transaction groups. A per pool tx_state structure
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* is used to track this information. The tx_state structure also points to
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* an array of tx_cpu structures (described above). Although the tx_sync_lock
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* is used to protect the members of this structure, it is not used to
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* protect the tx_open_txg. Instead a special lock in the tx_cpu structure
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* is used. Readers of tx_open_txg must grab the per-cpu tc_open_lock.
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* Any thread wishing to update tx_open_txg must grab the tc_open_lock on
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* every cpu (see txg_quiesce()).
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*/
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typedef struct tx_state {
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tx_cpu_t *tx_cpu; /* protects access to tx_open_txg */
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kmutex_t tx_sync_lock; /* protects the rest of this struct */
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uint64_t tx_open_txg; /* currently open txg id */
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uint64_t tx_quiescing_txg; /* currently quiescing txg id */
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uint64_t tx_quiesced_txg; /* quiesced txg waiting for sync */
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uint64_t tx_syncing_txg; /* currently syncing txg id */
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uint64_t tx_synced_txg; /* last synced txg id */
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hrtime_t tx_open_time; /* start time of tx_open_txg */
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uint64_t tx_sync_txg_waiting; /* txg we're waiting to sync */
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uint64_t tx_quiesce_txg_waiting; /* txg we're waiting to open */
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kcondvar_t tx_sync_more_cv;
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kcondvar_t tx_sync_done_cv;
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kcondvar_t tx_quiesce_more_cv;
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kcondvar_t tx_quiesce_done_cv;
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kcondvar_t tx_timeout_cv;
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kcondvar_t tx_exit_cv; /* wait for all threads to exit */
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uint8_t tx_threads; /* number of threads */
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uint8_t tx_exiting; /* set when we're exiting */
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kthread_t *tx_sync_thread;
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kthread_t *tx_quiesce_thread;
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taskq_t *tx_commit_cb_taskq; /* commit callback taskq */
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} tx_state_t;
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#ifdef __cplusplus
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}
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#endif
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#endif /* _SYS_TXG_IMPL_H */
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