diff options
Diffstat (limited to 'module')
| -rw-r--r-- | module/zfs/arc.c | 52 | ||||
| -rw-r--r-- | module/zfs/dbuf.c | 4 |
2 files changed, 54 insertions, 2 deletions
diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 476351eb4..45b0abe7f 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -449,8 +449,13 @@ typedef struct arc_stats { */ kstat_named_t arcstat_mutex_miss; /* + * Number of buffers skipped when updating the access state due to the + * header having already been released after acquiring the hash lock. + */ + kstat_named_t arcstat_access_skip; + /* * Number of buffers skipped because they have I/O in progress, are - * indrect prefetch buffers that have not lived long enough, or are + * indirect prefetch buffers that have not lived long enough, or are * not from the spa we're trying to evict from. */ kstat_named_t arcstat_evict_skip; @@ -688,6 +693,7 @@ static arc_stats_t arc_stats = { { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, { "deleted", KSTAT_DATA_UINT64 }, { "mutex_miss", KSTAT_DATA_UINT64 }, + { "access_skip", KSTAT_DATA_UINT64 }, { "evict_skip", KSTAT_DATA_UINT64 }, { "evict_not_enough", KSTAT_DATA_UINT64 }, { "evict_l2_cached", KSTAT_DATA_UINT64 }, @@ -5611,6 +5617,50 @@ arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) } } +/* + * This routine is called by dbuf_hold() to update the arc_access() state + * which otherwise would be skipped for entries in the dbuf cache. + */ +void +arc_buf_access(arc_buf_t *buf) +{ + mutex_enter(&buf->b_evict_lock); + arc_buf_hdr_t *hdr = buf->b_hdr; + + /* + * Avoid taking the hash_lock when possible as an optimization. + * The header must be checked again under the hash_lock in order + * to handle the case where it is concurrently being released. + */ + if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { + mutex_exit(&buf->b_evict_lock); + return; + } + + kmutex_t *hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + + if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { + mutex_exit(hash_lock); + mutex_exit(&buf->b_evict_lock); + ARCSTAT_BUMP(arcstat_access_skip); + return; + } + + mutex_exit(&buf->b_evict_lock); + + ASSERT(hdr->b_l1hdr.b_state == arc_mru || + hdr->b_l1hdr.b_state == arc_mfu); + + DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); + arc_access(hdr, hash_lock); + mutex_exit(hash_lock); + + ARCSTAT_BUMP(arcstat_hits); + ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr) && !HDR_PRESCIENT_PREFETCH(hdr), + demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits); +} + /* a generic arc_read_done_func_t which you can use */ /* ARGSUSED */ void diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c index 190d0656a..517a284de 100644 --- a/module/zfs/dbuf.c +++ b/module/zfs/dbuf.c @@ -2821,8 +2821,10 @@ __dbuf_hold_impl(struct dbuf_hold_impl_data *dh) return (SET_ERROR(ENOENT)); } - if (dh->dh_db->db_buf != NULL) + if (dh->dh_db->db_buf != NULL) { + arc_buf_access(dh->dh_db->db_buf); ASSERT3P(dh->dh_db->db.db_data, ==, dh->dh_db->db_buf->b_data); + } ASSERT(dh->dh_db->db_buf == NULL || arc_referenced(dh->dh_db->db_buf)); |