include/sys/zil_impl.h

   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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
  24  */
  25
  26 /* Portions Copyright 2010 Robert Milkowski */
  27
  28 #ifndef _SYS_ZIL_IMPL_H
  29 #define _SYS_ZIL_IMPL_H
  30
  31 #include <sys/zil.h>
  32 #include <sys/dmu_objset.h>
  33
  34 #ifdef  __cplusplus
  35 extern "C" {
  36 #endif
  37
  38 /*
  39  * Possible states for a given lwb structure.
  40  *
  41  * An lwb will start out in the "closed" state, and then transition to
  42  * the "opened" state via a call to zil_lwb_write_open(). When
  43  * transitioning from "closed" to "opened" the zilog's "zl_issuer_lock"
  44  * must be held.
  45  *
  46  * After the lwb is "opened", it can transition into the "issued" state
  47  * via zil_lwb_write_issue(). Again, the zilog's "zl_issuer_lock" must
  48  * be held when making this transition.
  49  *
  50  * After the lwb's write zio completes, it transitions into the "write
  51  * done" state via zil_lwb_write_done(); and then into the "flush done"
  52  * state via zil_lwb_flush_vdevs_done(). When transitioning from
  53  * "issued" to "write done", and then from "write done" to "flush done",
  54  * the zilog's "zl_lock" must be held, *not* the "zl_issuer_lock".
  55  *
  56  * The zilog's "zl_issuer_lock" can become heavily contended in certain
  57  * workloads, so we specifically avoid acquiring that lock when
  58  * transitioning an lwb from "issued" to "done". This allows us to avoid
  59  * having to acquire the "zl_issuer_lock" for each lwb ZIO completion,
  60  * which would have added more lock contention on an already heavily
  61  * contended lock.
  62  *
  63  * Additionally, correctness when reading an lwb's state is often
  64  * achieved by exploiting the fact that these state transitions occur in
  65  * this specific order; i.e. "closed" to "opened" to "issued" to "done".
  66  *
  67  * Thus, if an lwb is in the "closed" or "opened" state, holding the
  68  * "zl_issuer_lock" will prevent a concurrent thread from transitioning
  69  * that lwb to the "issued" state. Likewise, if an lwb is already in the
  70  * "issued" state, holding the "zl_lock" will prevent a concurrent
  71  * thread from transitioning that lwb to the "write done" state.
  72  */
  73 typedef enum {
  74     LWB_STATE_CLOSED,
  75     LWB_STATE_OPENED,
  76     LWB_STATE_ISSUED,
  77     LWB_STATE_WRITE_DONE,
  78     LWB_STATE_FLUSH_DONE,
  79     LWB_NUM_STATES
  80 } lwb_state_t;
  81
  82 /*
  83  * Log write block (lwb)
  84  *
  85  * Prior to an lwb being issued to disk via zil_lwb_write_issue(), it
  86  * will be protected by the zilog's "zl_issuer_lock". Basically, prior
  87  * to it being issued, it will only be accessed by the thread that's
  88  * holding the "zl_issuer_lock". After the lwb is issued, the zilog's
  89  * "zl_lock" is used to protect the lwb against concurrent access.
  90  */
  91 typedef struct lwb {
  92         zilog_t         *lwb_zilog;     /* back pointer to log struct */
  93         blkptr_t        lwb_blk;        /* on disk address of this log blk */
  94         boolean_t       lwb_fastwrite;  /* is blk marked for fastwrite? */
  95         boolean_t       lwb_slog;       /* lwb_blk is on SLOG device */
  96         int             lwb_nused;      /* # used bytes in buffer */
  97         int             lwb_sz;         /* size of block and buffer */
  98         lwb_state_t     lwb_state;      /* the state of this lwb */
  99         char            *lwb_buf;       /* log write buffer */
 100         zio_t           *lwb_write_zio; /* zio for the lwb buffer */
 101         zio_t           *lwb_root_zio;  /* root zio for lwb write and flushes */
 102         dmu_tx_t        *lwb_tx;        /* tx for log block allocation */
 103         uint64_t        lwb_max_txg;    /* highest txg in this lwb */
 104         list_node_t     lwb_node;       /* zilog->zl_lwb_list linkage */
 105         list_t          lwb_itxs;       /* list of itx's */
 106         list_t          lwb_waiters;    /* list of zil_commit_waiter's */
 107         avl_tree_t      lwb_vdev_tree;  /* vdevs to flush after lwb write */
 108         kmutex_t        lwb_vdev_lock;  /* protects lwb_vdev_tree */
 109         hrtime_t        lwb_issued_timestamp; /* when was the lwb issued? */
 110 } lwb_t;
 111
 112 /*
 113  * ZIL commit waiter.
 114  *
 115  * This structure is allocated each time zil_commit() is called, and is
 116  * used by zil_commit() to communicate with other parts of the ZIL, such
 117  * that zil_commit() can know when it safe for it return. For more
 118  * details, see the comment above zil_commit().
 119  *
 120  * The "zcw_lock" field is used to protect the commit waiter against
 121  * concurrent access. This lock is often acquired while already holding
 122  * the zilog's "zl_issuer_lock" or "zl_lock"; see the functions
 123  * zil_process_commit_list() and zil_lwb_flush_vdevs_done() as examples
 124  * of this. Thus, one must be careful not to acquire the
 125  * "zl_issuer_lock" or "zl_lock" when already holding the "zcw_lock";
 126  * e.g. see the zil_commit_waiter_timeout() function.
 127  */
 128 typedef struct zil_commit_waiter {
 129         kcondvar_t      zcw_cv;         /* signalled when "done" */
 130         kmutex_t        zcw_lock;       /* protects fields of this struct */
 131         list_node_t     zcw_node;       /* linkage in lwb_t:lwb_waiter list */
 132         lwb_t           *zcw_lwb;       /* back pointer to lwb when linked */
 133         boolean_t       zcw_done;       /* B_TRUE when "done", else B_FALSE */
 134         int             zcw_zio_error;  /* contains the zio io_error value */
 135 } zil_commit_waiter_t;
 136
 137 /*
 138  * Intent log transaction lists
 139  */
 140 typedef struct itxs {
 141         list_t          i_sync_list;    /* list of synchronous itxs */
 142         avl_tree_t      i_async_tree;   /* tree of foids for async itxs */
 143 } itxs_t;
 144
 145 typedef struct itxg {
 146         kmutex_t        itxg_lock;      /* lock for this structure */
 147         uint64_t        itxg_txg;       /* txg for this chain */
 148         itxs_t          *itxg_itxs;     /* sync and async itxs */
 149 } itxg_t;
 150
 151 /* for async nodes we build up an AVL tree of lists of async itxs per file */
 152 typedef struct itx_async_node {
 153         uint64_t        ia_foid;        /* file object id */
 154         list_t          ia_list;        /* list of async itxs for this foid */
 155         avl_node_t      ia_node;        /* AVL tree linkage */
 156 } itx_async_node_t;
 157
 158 /*
 159  * Vdev flushing: during a zil_commit(), we build up an AVL tree of the vdevs
 160  * we've touched so we know which ones need a write cache flush at the end.
 161  */
 162 typedef struct zil_vdev_node {
 163         uint64_t        zv_vdev;        /* vdev to be flushed */
 164         avl_node_t      zv_node;        /* AVL tree linkage */
 165 } zil_vdev_node_t;
 166
 167 #define ZIL_PREV_BLKS 16
 168
 169 /*
 170  * Stable storage intent log management structure.  One per dataset.
 171  */
 172 struct zilog {
 173         kmutex_t        zl_lock;        /* protects most zilog_t fields */
 174         struct dsl_pool *zl_dmu_pool;   /* DSL pool */
 175         spa_t           *zl_spa;        /* handle for read/write log */
 176         const zil_header_t *zl_header;  /* log header buffer */
 177         objset_t        *zl_os;         /* object set we're logging */
 178         zil_get_data_t  *zl_get_data;   /* callback to get object content */
 179         lwb_t           *zl_last_lwb_opened; /* most recent lwb opened */
 180         hrtime_t        zl_last_lwb_latency; /* zio latency of last lwb done */
 181         uint64_t        zl_lr_seq;      /* on-disk log record sequence number */
 182         uint64_t        zl_commit_lr_seq; /* last committed on-disk lr seq */
 183         uint64_t        zl_destroy_txg; /* txg of last zil_destroy() */
 184         uint64_t        zl_replayed_seq[TXG_SIZE]; /* last replayed rec seq */
 185         uint64_t        zl_replaying_seq; /* current replay seq number */
 186         uint32_t        zl_suspend;     /* log suspend count */
 187         kcondvar_t      zl_cv_suspend;  /* log suspend completion */
 188         uint8_t         zl_suspending;  /* log is currently suspending */
 189         uint8_t         zl_keep_first;  /* keep first log block in destroy */
 190         uint8_t         zl_replay;      /* replaying records while set */
 191         uint8_t         zl_stop_sync;   /* for debugging */
 192         kmutex_t        zl_issuer_lock; /* single writer, per ZIL, at a time */
 193         uint8_t         zl_logbias;     /* latency or throughput */
 194         uint8_t         zl_sync;        /* synchronous or asynchronous */
 195         int             zl_parse_error; /* last zil_parse() error */
 196         uint64_t        zl_parse_blk_seq; /* highest blk seq on last parse */
 197         uint64_t        zl_parse_lr_seq; /* highest lr seq on last parse */
 198         uint64_t        zl_parse_blk_count; /* number of blocks parsed */
 199         uint64_t        zl_parse_lr_count; /* number of log records parsed */
 200         itxg_t          zl_itxg[TXG_SIZE]; /* intent log txg chains */
 201         list_t          zl_itx_commit_list; /* itx list to be committed */
 202         uint64_t        zl_cur_used;    /* current commit log size used */
 203         list_t          zl_lwb_list;    /* in-flight log write list */
 204         avl_tree_t      zl_bp_tree;     /* track bps during log parse */
 205         clock_t         zl_replay_time; /* lbolt of when replay started */
 206         uint64_t        zl_replay_blks; /* number of log blocks replayed */
 207         zil_header_t    zl_old_header;  /* debugging aid */
 208         uint_t          zl_prev_blks[ZIL_PREV_BLKS]; /* size - sector rounded */
 209         uint_t          zl_prev_rotor;  /* rotor for zl_prev[] */
 210         txg_node_t      zl_dirty_link;  /* protected by dp_dirty_zilogs list */
 211         uint64_t        zl_dirty_max_txg; /* highest txg used to dirty zilog */
 212 };
 213
 214 typedef struct zil_bp_node {
 215         dva_t           zn_dva;
 216         avl_node_t      zn_node;
 217 } zil_bp_node_t;
 218
 219 /*
 220  * Maximum amount of write data that can be put into single log block.
 221  */
 222 #define ZIL_MAX_LOG_DATA (SPA_OLD_MAXBLOCKSIZE - sizeof (zil_chain_t) - \
 223     sizeof (lr_write_t))
 224
 225 /*
 226  * Maximum amount of log space we agree to waste to reduce number of
 227  * WR_NEED_COPY chunks to reduce zl_get_data() overhead (~12%).
 228  */
 229 #define ZIL_MAX_WASTE_SPACE (ZIL_MAX_LOG_DATA / 8)
 230
 231 /*
 232  * Maximum amount of write data for WR_COPIED.  Fall back to WR_NEED_COPY
 233  * as more space efficient if we can't fit at least two log records into
 234  * maximum sized log block.
 235  */
 236 #define ZIL_MAX_COPIED_DATA ((SPA_OLD_MAXBLOCKSIZE - \
 237     sizeof (zil_chain_t)) / 2 - sizeof (lr_write_t))
 238
 239 #ifdef  __cplusplus
 240 }
 241 #endif
 242
 243 #endif  /* _SYS_ZIL_IMPL_H */