Author: delphij
Date: Fri Jul 18 18:02:34 2014
New Revision: 268850
URL: http://svnweb.freebsd.org/changeset/base/268850
Log:
4631 zvol_get_stats triggering too many reads
Reviewed by: Adam Leventhal <a...@delphix.com>
Reviewed by: Sebastien Roy <sebastien....@delphix.com>
Reviewed by: Matt Ahrens <mahr...@delphix.com>
Approved by: Dan McDonald <dan...@omniti.com>
illumos/illumos-gate@bbfa8ea8bb4168c969ba27d632dfe0aeec3fc0da
Modified:
vendor-sys/illumos/dist/uts/common/fs/zfs/arc.c
vendor-sys/illumos/dist/uts/common/fs/zfs/dbuf.c
vendor-sys/illumos/dist/uts/common/fs/zfs/sys/arc.h
Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/arc.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/arc.c Fri Jul 18 18:00:00
2014 (r268849)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/arc.c Fri Jul 18 18:02:34
2014 (r268850)
@@ -105,7 +105,7 @@
* with the buffer may be evicted prior to the callback. The callback
* must be made with *no locks held* (to prevent deadlock). Additionally,
* the users of callbacks must ensure that their private data is
- * protected from simultaneous callbacks from arc_buf_evict()
+ * protected from simultaneous callbacks from arc_clear_callback()
* and arc_do_user_evicts().
*
* Note that the majority of the performance stats are manipulated
@@ -1495,8 +1495,12 @@ arc_buf_data_free(arc_buf_t *buf, void (
}
}
+/*
+ * Free up buf->b_data and if 'remove' is set, then pull the
+ * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
+ */
static void
-arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
+arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove)
{
arc_buf_t **bufp;
@@ -1547,7 +1551,7 @@ arc_buf_destroy(arc_buf_t *buf, boolean_
}
/* only remove the buf if requested */
- if (!all)
+ if (!remove)
return;
/* remove the buf from the hdr list */
@@ -2121,7 +2125,7 @@ arc_do_user_evicts(void)
mutex_exit(&arc_eviction_mtx);
if (buf->b_efunc != NULL)
- VERIFY(buf->b_efunc(buf) == 0);
+ VERIFY0(buf->b_efunc(buf->b_private));
buf->b_efunc = NULL;
buf->b_private = NULL;
@@ -3240,16 +3244,25 @@ arc_freed(spa_t *spa, const blkptr_t *bp
}
/*
- * This is used by the DMU to let the ARC know that a buffer is
- * being evicted, so the ARC should clean up. If this arc buf
- * is not yet in the evicted state, it will be put there.
+ * Clear the user eviction callback set by arc_set_callback(), first calling
+ * it if it exists. Because the presence of a callback keeps an arc_buf cached
+ * clearing the callback may result in the arc_buf being destroyed. However,
+ * it will not result in the *last* arc_buf being destroyed, hence the data
+ * will remain cached in the ARC. We make a copy of the arc buffer here so
+ * that we can process the callback without holding any locks.
+ *
+ * It's possible that the callback is already in the process of being cleared
+ * by another thread. In this case we can not clear the callback.
+ *
+ * Returns B_TRUE if the callback was successfully called and cleared.
*/
-int
-arc_buf_evict(arc_buf_t *buf)
+boolean_t
+arc_clear_callback(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
- arc_buf_t **bufp;
+ arc_evict_func_t *efunc = buf->b_efunc;
+ void *private = buf->b_private;
mutex_enter(&buf->b_evict_lock);
hdr = buf->b_hdr;
@@ -3259,17 +3272,16 @@ arc_buf_evict(arc_buf_t *buf)
*/
ASSERT(buf->b_data == NULL);
mutex_exit(&buf->b_evict_lock);
- return (0);
+ return (B_FALSE);
} else if (buf->b_data == NULL) {
- arc_buf_t copy = *buf; /* structure assignment */
/*
* We are on the eviction list; process this buffer now
* but let arc_do_user_evicts() do the reaping.
*/
buf->b_efunc = NULL;
mutex_exit(&buf->b_evict_lock);
- VERIFY(copy.b_efunc(©) == 0);
- return (1);
+ VERIFY0(efunc(private));
+ return (B_TRUE);
}
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
@@ -3279,48 +3291,21 @@ arc_buf_evict(arc_buf_t *buf)
ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
- /*
- * Pull this buffer off of the hdr
- */
- bufp = &hdr->b_buf;
- while (*bufp != buf)
- bufp = &(*bufp)->b_next;
- *bufp = buf->b_next;
-
- ASSERT(buf->b_data != NULL);
- arc_buf_destroy(buf, FALSE, FALSE);
-
- if (hdr->b_datacnt == 0) {
- arc_state_t *old_state = hdr->b_state;
- arc_state_t *evicted_state;
-
- ASSERT(hdr->b_buf == NULL);
- ASSERT(refcount_is_zero(&hdr->b_refcnt));
-
- evicted_state =
- (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
-
- mutex_enter(&old_state->arcs_mtx);
- mutex_enter(&evicted_state->arcs_mtx);
-
- arc_change_state(evicted_state, hdr, hash_lock);
- ASSERT(HDR_IN_HASH_TABLE(hdr));
- hdr->b_flags |= ARC_IN_HASH_TABLE;
- hdr->b_flags &= ~ARC_BUF_AVAILABLE;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
- mutex_exit(&evicted_state->arcs_mtx);
- mutex_exit(&old_state->arcs_mtx);
+ if (hdr->b_datacnt > 1) {
+ mutex_exit(&buf->b_evict_lock);
+ arc_buf_destroy(buf, FALSE, TRUE);
+ } else {
+ ASSERT(buf == hdr->b_buf);
+ hdr->b_flags |= ARC_BUF_AVAILABLE;
+ mutex_exit(&buf->b_evict_lock);
}
- mutex_exit(hash_lock);
- mutex_exit(&buf->b_evict_lock);
- VERIFY(buf->b_efunc(buf) == 0);
- buf->b_efunc = NULL;
- buf->b_private = NULL;
- buf->b_hdr = NULL;
- buf->b_next = NULL;
- kmem_cache_free(buf_cache, buf);
- return (1);
+ mutex_exit(hash_lock);
+ VERIFY0(efunc(private));
+ return (B_TRUE);
}
/*
@@ -3466,17 +3451,6 @@ arc_released(arc_buf_t *buf)
return (released);
}
-int
-arc_has_callback(arc_buf_t *buf)
-{
- int callback;
-
- mutex_enter(&buf->b_evict_lock);
- callback = (buf->b_efunc != NULL);
- mutex_exit(&buf->b_evict_lock);
- return (callback);
-}
-
#ifdef ZFS_DEBUG
int
arc_referenced(arc_buf_t *buf)
Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/dbuf.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/dbuf.c Fri Jul 18 18:00:00
2014 (r268849)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/dbuf.c Fri Jul 18 18:02:34
2014 (r268850)
@@ -181,8 +181,7 @@ dbuf_hash_insert(dmu_buf_impl_t *db)
}
/*
- * Remove an entry from the hash table. This operation will
- * fail if there are any existing holds on the db.
+ * Remove an entry from the hash table. It must be in the EVICTING state.
*/
static void
dbuf_hash_remove(dmu_buf_impl_t *db)
@@ -194,7 +193,7 @@ dbuf_hash_remove(dmu_buf_impl_t *db)
dmu_buf_impl_t *dbf, **dbp;
/*
- * We musn't hold db_mtx to maintin lock ordering:
+ * We musn't hold db_mtx to maintain lock ordering:
* DBUF_HASH_MUTEX > db_mtx.
*/
ASSERT(refcount_is_zero(&db->db_holds));
@@ -431,7 +430,6 @@ static void
dbuf_set_data(dmu_buf_impl_t *db, arc_buf_t *buf)
{
ASSERT(MUTEX_HELD(&db->db_mtx));
- ASSERT(db->db_buf == NULL || !arc_has_callback(db->db_buf));
db->db_buf = buf;
if (buf != NULL) {
ASSERT(buf->b_data != NULL);
@@ -1544,12 +1542,15 @@ dbuf_assign_arcbuf(dmu_buf_impl_t *db, a
* when we are not holding the dn_dbufs_mtx, we can't clear the
* entry in the dn_dbufs list. We have to wait until dbuf_destroy()
* in this case. For callers from the DMU we will usually see:
- * dbuf_clear()->arc_buf_evict()->dbuf_do_evict()->dbuf_destroy()
+ * dbuf_clear()->arc_clear_callback()->dbuf_do_evict()->dbuf_destroy()
* For the arc callback, we will usually see:
* dbuf_do_evict()->dbuf_clear();dbuf_destroy()
* Sometimes, though, we will get a mix of these two:
- * DMU: dbuf_clear()->arc_buf_evict()
+ * DMU: dbuf_clear()->arc_clear_callback()
* ARC: dbuf_do_evict()->dbuf_destroy()
+ *
+ * This routine will dissociate the dbuf from the arc, by calling
+ * arc_clear_callback(), but will not evict the data from the ARC.
*/
void
dbuf_clear(dmu_buf_impl_t *db)
@@ -1557,7 +1558,7 @@ dbuf_clear(dmu_buf_impl_t *db)
dnode_t *dn;
dmu_buf_impl_t *parent = db->db_parent;
dmu_buf_impl_t *dndb;
- int dbuf_gone = FALSE;
+ boolean_t dbuf_gone = B_FALSE;
ASSERT(MUTEX_HELD(&db->db_mtx));
ASSERT(refcount_is_zero(&db->db_holds));
@@ -1603,7 +1604,7 @@ dbuf_clear(dmu_buf_impl_t *db)
}
if (db->db_buf)
- dbuf_gone = arc_buf_evict(db->db_buf);
+ dbuf_gone = arc_clear_callback(db->db_buf);
if (!dbuf_gone)
mutex_exit(&db->db_mtx);
@@ -1771,8 +1772,7 @@ dbuf_create(dnode_t *dn, uint8_t level,
static int
dbuf_do_evict(void *private)
{
- arc_buf_t *buf = private;
- dmu_buf_impl_t *db = buf->b_private;
+ dmu_buf_impl_t *db = private;
if (!MUTEX_HELD(&db->db_mtx))
mutex_enter(&db->db_mtx);
@@ -2135,11 +2135,23 @@ dbuf_rele_and_unlock(dmu_buf_impl_t *db,
* block on-disk. If so, then we simply evict
* ourselves.
*/
- if (!DBUF_IS_CACHEABLE(db) ||
- arc_buf_eviction_needed(db->db_buf))
+ if (!DBUF_IS_CACHEABLE(db)) {
+ if (db->db_blkptr != NULL &&
+ !BP_IS_HOLE(db->db_blkptr) &&
+ !BP_IS_EMBEDDED(db->db_blkptr)) {
+ spa_t *spa =
+ dmu_objset_spa(db->db_objset);
+ blkptr_t bp = *db->db_blkptr;
+ dbuf_clear(db);
+ arc_freed(spa, &bp);
+ } else {
+ dbuf_clear(db);
+ }
+ } else if (arc_buf_eviction_needed(db->db_buf)) {
dbuf_clear(db);
- else
+ } else {
mutex_exit(&db->db_mtx);
+ }
}
} else {
mutex_exit(&db->db_mtx);
Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/sys/arc.h
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/sys/arc.h Fri Jul 18 18:00:00
2014 (r268849)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/sys/arc.h Fri Jul 18 18:02:34
2014 (r268850)
@@ -95,7 +95,6 @@ boolean_t arc_buf_remove_ref(arc_buf_t *
int arc_buf_size(arc_buf_t *buf);
void arc_release(arc_buf_t *buf, void *tag);
int arc_released(arc_buf_t *buf);
-int arc_has_callback(arc_buf_t *buf);
void arc_buf_freeze(arc_buf_t *buf);
void arc_buf_thaw(arc_buf_t *buf);
boolean_t arc_buf_eviction_needed(arc_buf_t *buf);
@@ -114,7 +113,7 @@ zio_t *arc_write(zio_t *pio, spa_t *spa,
void arc_freed(spa_t *spa, const blkptr_t *bp);
void arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private);
-int arc_buf_evict(arc_buf_t *buf);
+boolean_t arc_clear_callback(arc_buf_t *buf);
void arc_flush(spa_t *spa);
void arc_tempreserve_clear(uint64_t reserve);
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