diff options
Diffstat (limited to 'module/zfs/arc.c')
| -rw-r--r-- | module/zfs/arc.c | 84 |
1 files changed, 83 insertions, 1 deletions
diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 5d9b34fbf..5e21b1b71 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -189,6 +189,7 @@ unsigned long zfs_arc_meta_limit = 0; int zfs_arc_grow_retry = 0; int zfs_arc_shrink_shift = 0; int zfs_arc_p_min_shift = 0; +int zfs_disable_dup_eviction = 0; int zfs_arc_meta_prune = 0; /* @@ -307,6 +308,9 @@ typedef struct arc_stats { kstat_named_t arcstat_l2_size; kstat_named_t arcstat_l2_hdr_size; kstat_named_t arcstat_memory_throttle_count; + kstat_named_t arcstat_duplicate_buffers; + kstat_named_t arcstat_duplicate_buffers_size; + kstat_named_t arcstat_duplicate_reads; kstat_named_t arcstat_memory_direct_count; kstat_named_t arcstat_memory_indirect_count; kstat_named_t arcstat_no_grow; @@ -387,6 +391,9 @@ static arc_stats_t arc_stats = { { "l2_size", KSTAT_DATA_UINT64 }, { "l2_hdr_size", KSTAT_DATA_UINT64 }, { "memory_throttle_count", KSTAT_DATA_UINT64 }, + { "duplicate_buffers", KSTAT_DATA_UINT64 }, + { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, + { "duplicate_reads", KSTAT_DATA_UINT64 }, { "memory_direct_count", KSTAT_DATA_UINT64 }, { "memory_indirect_count", KSTAT_DATA_UINT64 }, { "arc_no_grow", KSTAT_DATA_UINT64 }, @@ -1369,6 +1376,17 @@ arc_buf_clone(arc_buf_t *from) hdr->b_buf = buf; arc_get_data_buf(buf); bcopy(from->b_data, buf->b_data, size); + + /* + * This buffer already exists in the arc so create a duplicate + * copy for the caller. If the buffer is associated with user data + * then track the size and number of duplicates. These stats will be + * updated as duplicate buffers are created and destroyed. + */ + if (hdr->b_type == ARC_BUFC_DATA) { + ARCSTAT_BUMP(arcstat_duplicate_buffers); + ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); + } hdr->b_datacnt += 1; return (buf); } @@ -1467,6 +1485,16 @@ arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all) ASSERT3U(state->arcs_size, >=, size); atomic_add_64(&state->arcs_size, -size); buf->b_data = NULL; + + /* + * If we're destroying a duplicate buffer make sure + * that the appropriate statistics are updated. + */ + if (buf->b_hdr->b_datacnt > 1 && + buf->b_hdr->b_type == ARC_BUFC_DATA) { + ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); + ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); + } ASSERT(buf->b_hdr->b_datacnt > 0); buf->b_hdr->b_datacnt -= 1; } @@ -1652,6 +1680,48 @@ arc_buf_size(arc_buf_t *buf) } /* + * Called from the DMU to determine if the current buffer should be + * evicted. In order to ensure proper locking, the eviction must be initiated + * from the DMU. Return true if the buffer is associated with user data and + * duplicate buffers still exist. + */ +boolean_t +arc_buf_eviction_needed(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr; + boolean_t evict_needed = B_FALSE; + + if (zfs_disable_dup_eviction) + return (B_FALSE); + + mutex_enter(&buf->b_evict_lock); + hdr = buf->b_hdr; + if (hdr == NULL) { + /* + * We are in arc_do_user_evicts(); let that function + * perform the eviction. + */ + ASSERT(buf->b_data == NULL); + mutex_exit(&buf->b_evict_lock); + return (B_FALSE); + } else if (buf->b_data == NULL) { + /* + * We have already been added to the arc eviction list; + * recommend eviction. + */ + ASSERT3P(hdr, ==, &arc_eviction_hdr); + mutex_exit(&buf->b_evict_lock); + return (B_TRUE); + } + + if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA) + evict_needed = B_TRUE; + + mutex_exit(&buf->b_evict_lock); + return (evict_needed); +} + +/* * Evict buffers from list until we've removed the specified number of * bytes. Move the removed buffers to the appropriate evict state. * If the recycle flag is set, then attempt to "recycle" a buffer: @@ -2753,8 +2823,10 @@ arc_read_done(zio_t *zio) abuf = buf; for (acb = callback_list; acb; acb = acb->acb_next) { if (acb->acb_done) { - if (abuf == NULL) + if (abuf == NULL) { + ARCSTAT_BUMP(arcstat_duplicate_reads); abuf = arc_buf_clone(buf); + } acb->acb_buf = abuf; abuf = NULL; } @@ -3324,6 +3396,16 @@ arc_release(arc_buf_t *buf, void *tag) ASSERT3U(*size, >=, hdr->b_size); atomic_add_64(size, -hdr->b_size); } + + /* + * We're releasing a duplicate user data buffer, update + * our statistics accordingly. + */ + if (hdr->b_type == ARC_BUFC_DATA) { + ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); + ARCSTAT_INCR(arcstat_duplicate_buffers_size, + -hdr->b_size); + } hdr->b_datacnt -= 1; arc_cksum_verify(buf); |