txg_impl.h revision 4a92375985c37d61406d66cd2b10ee642eb1f5e7
/*
* 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 */
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 */