diff options
Diffstat (limited to 'include/sys/arc_impl.h')
| -rw-r--r-- | include/sys/arc_impl.h | 95 |
1 files changed, 74 insertions, 21 deletions
diff --git a/include/sys/arc_impl.h b/include/sys/arc_impl.h index 1f8351a67..556cc2583 100644 --- a/include/sys/arc_impl.h +++ b/include/sys/arc_impl.h @@ -74,8 +74,6 @@ typedef struct arc_state { arc_state_type_t arcs_state; } arc_state_t; -typedef struct l2arc_buf_hdr l2arc_buf_hdr_t; - typedef struct arc_callback arc_callback_t; struct arc_callback { @@ -96,27 +94,45 @@ struct arc_write_callback { arc_buf_t *awcb_buf; }; -struct arc_buf_hdr { - /* protected by hash lock */ - dva_t b_dva; - uint64_t b_birth; - uint64_t b_cksum0; - +/* + * ARC buffers are separated into multiple structs as a memory saving measure: + * - Common fields struct, always defined, and embedded within it: + * - L2-only fields, always allocated but undefined when not in L2ARC + * - L1-only fields, only allocated when in L1ARC + * + * Buffer in L1 Buffer only in L2 + * +------------------------+ +------------------------+ + * | arc_buf_hdr_t | | arc_buf_hdr_t | + * | | | | + * | | | | + * | | | | + * +------------------------+ +------------------------+ + * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | + * | (undefined if L1-only) | | | + * +------------------------+ +------------------------+ + * | l1arc_buf_hdr_t | + * | | + * | | + * | | + * | | + * +------------------------+ + * + * Because it's possible for the L2ARC to become extremely large, we can wind + * up eating a lot of memory in L2ARC buffer headers, so the size of a header + * is minimized by only allocating the fields necessary for an L1-cached buffer + * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and + * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple + * words in pointers. arc_hdr_realloc() is used to switch a header between + * these two allocation states. + */ +typedef struct l1arc_buf_hdr { kmutex_t b_freeze_lock; - zio_cksum_t *b_freeze_cksum; - arc_buf_hdr_t *b_hash_next; arc_buf_t *b_buf; - arc_flags_t b_flags; uint32_t b_datacnt; - - arc_callback_t *b_acb; + /* for waiting on writes to complete */ kcondvar_t b_cv; - /* immutable */ - arc_buf_contents_t b_type; - uint64_t b_size; - uint64_t b_spa; /* protected by arc state mutex */ arc_state_t *b_state; @@ -133,9 +149,10 @@ struct arc_buf_hdr { /* self protecting */ refcount_t b_refcnt; - l2arc_buf_hdr_t *b_l2hdr; - list_node_t b_l2node; -}; + arc_callback_t *b_acb; + /* temporary buffer holder for in-flight compressed data */ + void *b_tmp_cdata; +} l1arc_buf_hdr_t; typedef struct l2arc_dev { vdev_t *l2ad_vdev; /* vdev */ @@ -146,15 +163,51 @@ typedef struct l2arc_dev { uint64_t l2ad_evict; /* last addr eviction reached */ boolean_t l2ad_first; /* first sweep through */ boolean_t l2ad_writing; /* currently writing */ - list_t *l2ad_buflist; /* buffer list */ + kmutex_t l2ad_mtx; /* lock for buffer list */ + list_t l2ad_buflist; /* buffer list */ list_node_t l2ad_node; /* device list node */ } l2arc_dev_t; +typedef struct l2arc_buf_hdr { + /* protected by arc_buf_hdr mutex */ + l2arc_dev_t *b_dev; /* L2ARC device */ + uint64_t b_daddr; /* disk address, offset byte */ + /* real alloc'd buffer size depending on b_compress applied */ + uint32_t b_hits; + int32_t b_asize; + + list_node_t b_l2node; +} l2arc_buf_hdr_t; + typedef struct l2arc_write_callback { l2arc_dev_t *l2wcb_dev; /* device info */ arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ } l2arc_write_callback_t; +struct arc_buf_hdr { + /* protected by hash lock */ + dva_t b_dva; + uint64_t b_birth; + /* + * Even though this checksum is only set/verified when a buffer is in + * the L1 cache, it needs to be in the set of common fields because it + * must be preserved from the time before a buffer is written out to + * L2ARC until after it is read back in. + */ + zio_cksum_t *b_freeze_cksum; + + arc_buf_hdr_t *b_hash_next; + arc_flags_t b_flags; + + /* immutable */ + int32_t b_size; + uint64_t b_spa; + + /* L2ARC fields. Undefined when not in L2ARC. */ + l2arc_buf_hdr_t b_l2hdr; + /* L1ARC fields. Undefined when in l2arc_only state */ + l1arc_buf_hdr_t b_l1hdr; +}; #ifdef __cplusplus } #endif |