246 lines
8.2 KiB
C
246 lines
8.2 KiB
C
/*
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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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 2013 by Delphix. All rights reserved.
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* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
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* Copyright 2013 Nexenta Systems, Inc. All rights reserved.
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*/
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#ifndef _SYS_ARC_IMPL_H
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#define _SYS_ARC_IMPL_H
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#include <sys/arc.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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* Note that buffers can be in one of 6 states:
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* ARC_anon - anonymous (discussed below)
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* ARC_mru - recently used, currently cached
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* ARC_mru_ghost - recentely used, no longer in cache
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* ARC_mfu - frequently used, currently cached
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* ARC_mfu_ghost - frequently used, no longer in cache
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* ARC_l2c_only - exists in L2ARC but not other states
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* When there are no active references to the buffer, they are
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* are linked onto a list in one of these arc states. These are
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* the only buffers that can be evicted or deleted. Within each
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* state there are multiple lists, one for meta-data and one for
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* non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
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* etc.) is tracked separately so that it can be managed more
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* explicitly: favored over data, limited explicitly.
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*
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* Anonymous buffers are buffers that are not associated with
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* a DVA. These are buffers that hold dirty block copies
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* before they are written to stable storage. By definition,
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* they are "ref'd" and are considered part of arc_mru
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* that cannot be freed. Generally, they will aquire a DVA
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* as they are written and migrate onto the arc_mru list.
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*
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* The ARC_l2c_only state is for buffers that are in the second
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* level ARC but no longer in any of the ARC_m* lists. The second
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* level ARC itself may also contain buffers that are in any of
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* the ARC_m* states - meaning that a buffer can exist in two
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* places. The reason for the ARC_l2c_only state is to keep the
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* buffer header in the hash table, so that reads that hit the
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* second level ARC benefit from these fast lookups.
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*/
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typedef struct arc_state {
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/*
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* list of evictable buffers
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*/
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multilist_t arcs_list[ARC_BUFC_NUMTYPES];
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/*
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* total amount of evictable data in this state
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*/
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refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
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/*
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* total amount of data in this state; this includes: evictable,
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* non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
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*/
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refcount_t arcs_size;
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/*
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* supports the "dbufs" kstat
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*/
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arc_state_type_t arcs_state;
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} arc_state_t;
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typedef struct arc_callback arc_callback_t;
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struct arc_callback {
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void *acb_private;
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arc_done_func_t *acb_done;
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arc_buf_t *acb_buf;
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boolean_t acb_compressed;
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zio_t *acb_zio_dummy;
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arc_callback_t *acb_next;
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};
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typedef struct arc_write_callback arc_write_callback_t;
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struct arc_write_callback {
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void *awcb_private;
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arc_done_func_t *awcb_ready;
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arc_done_func_t *awcb_children_ready;
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arc_done_func_t *awcb_physdone;
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arc_done_func_t *awcb_done;
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arc_buf_t *awcb_buf;
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};
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/*
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* ARC buffers are separated into multiple structs as a memory saving measure:
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* - Common fields struct, always defined, and embedded within it:
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* - L2-only fields, always allocated but undefined when not in L2ARC
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* - L1-only fields, only allocated when in L1ARC
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*
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* Buffer in L1 Buffer only in L2
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* +------------------------+ +------------------------+
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* | arc_buf_hdr_t | | arc_buf_hdr_t |
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* | | | |
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* | | | |
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* | | | |
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* +------------------------+ +------------------------+
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* | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
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* | (undefined if L1-only) | | |
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* +------------------------+ +------------------------+
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* | l1arc_buf_hdr_t |
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* | |
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* | |
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* | |
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* | |
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* +------------------------+
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*
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* Because it's possible for the L2ARC to become extremely large, we can wind
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* up eating a lot of memory in L2ARC buffer headers, so the size of a header
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* is minimized by only allocating the fields necessary for an L1-cached buffer
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* when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
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* l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
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* words in pointers. arc_hdr_realloc() is used to switch a header between
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* these two allocation states.
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*/
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typedef struct l1arc_buf_hdr {
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kmutex_t b_freeze_lock;
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zio_cksum_t *b_freeze_cksum;
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arc_buf_t *b_buf;
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uint32_t b_bufcnt;
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/* for waiting on writes to complete */
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kcondvar_t b_cv;
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uint8_t b_byteswap;
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/* protected by arc state mutex */
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arc_state_t *b_state;
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multilist_node_t b_arc_node;
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/* updated atomically */
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clock_t b_arc_access;
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uint32_t b_mru_hits;
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uint32_t b_mru_ghost_hits;
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uint32_t b_mfu_hits;
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uint32_t b_mfu_ghost_hits;
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uint32_t b_l2_hits;
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/* self protecting */
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refcount_t b_refcnt;
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arc_callback_t *b_acb;
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abd_t *b_pabd;
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} l1arc_buf_hdr_t;
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typedef struct l2arc_dev {
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vdev_t *l2ad_vdev; /* vdev */
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spa_t *l2ad_spa; /* spa */
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uint64_t l2ad_hand; /* next write location */
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uint64_t l2ad_start; /* first addr on device */
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uint64_t l2ad_end; /* last addr on device */
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boolean_t l2ad_first; /* first sweep through */
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boolean_t l2ad_writing; /* currently writing */
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kmutex_t l2ad_mtx; /* lock for buffer list */
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list_t l2ad_buflist; /* buffer list */
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list_node_t l2ad_node; /* device list node */
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refcount_t l2ad_alloc; /* allocated bytes */
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} l2arc_dev_t;
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typedef struct l2arc_buf_hdr {
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/* protected by arc_buf_hdr mutex */
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l2arc_dev_t *b_dev; /* L2ARC device */
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uint64_t b_daddr; /* disk address, offset byte */
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uint32_t b_hits;
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list_node_t b_l2node;
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} l2arc_buf_hdr_t;
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typedef struct l2arc_write_callback {
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l2arc_dev_t *l2wcb_dev; /* device info */
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arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
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} l2arc_write_callback_t;
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struct arc_buf_hdr {
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/* protected by hash lock */
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dva_t b_dva;
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uint64_t b_birth;
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arc_buf_contents_t b_type;
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arc_buf_hdr_t *b_hash_next;
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arc_flags_t b_flags;
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/*
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* This field stores the size of the data buffer after
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* compression, and is set in the arc's zio completion handlers.
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* It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
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*
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* While the block pointers can store up to 32MB in their psize
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* field, we can only store up to 32MB minus 512B. This is due
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* to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
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* a field of zeros represents 512B in the bp). We can't use a
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* bias of 1 since we need to reserve a psize of zero, here, to
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* represent holes and embedded blocks.
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*
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* This isn't a problem in practice, since the maximum size of a
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* buffer is limited to 16MB, so we never need to store 32MB in
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* this field. Even in the upstream illumos code base, the
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* maximum size of a buffer is limited to 16MB.
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*/
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uint16_t b_psize;
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/*
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* This field stores the size of the data buffer before
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* compression, and cannot change once set. It is in units
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* of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
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*/
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uint16_t b_lsize; /* immutable */
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uint64_t b_spa; /* immutable */
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/* L2ARC fields. Undefined when not in L2ARC. */
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l2arc_buf_hdr_t b_l2hdr;
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/* L1ARC fields. Undefined when in l2arc_only state */
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l1arc_buf_hdr_t b_l1hdr;
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};
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#ifdef __cplusplus
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}
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#endif
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#endif /* _SYS_ARC_IMPL_H */
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