#include <sys/dnode.h>
#include <sys/zap.h>
#include <sys/zfeature.h>
+#include <sys/dsl_dataset.h>
+
+/*
+ * Each of the concurrent object allocators will grab
+ * 2^dmu_object_alloc_chunk_shift dnode slots at a time. The default is to
+ * grab 128 slots, which is 4 blocks worth. This was experimentally
+ * determined to be the lowest value that eliminates the measurable effect
+ * of lock contention from this code path.
+ */
+int dmu_object_alloc_chunk_shift = 7;
uint64_t
dmu_object_alloc(objset_t *os, dmu_object_type_t ot, int blocksize,
dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
+{
+ return dmu_object_alloc_dnsize(os, ot, blocksize, bonustype, bonuslen,
+ 0, tx);
+}
+
+uint64_t
+dmu_object_alloc_dnsize(objset_t *os, dmu_object_type_t ot, int blocksize,
+ dmu_object_type_t bonustype, int bonuslen, int dnodesize, dmu_tx_t *tx)
{
uint64_t object;
- uint64_t L2_dnode_count = DNODES_PER_BLOCK <<
+ uint64_t L1_dnode_count = DNODES_PER_BLOCK <<
(DMU_META_DNODE(os)->dn_indblkshift - SPA_BLKPTRSHIFT);
dnode_t *dn = NULL;
- int restarted = B_FALSE;
+ int dn_slots = dnodesize >> DNODE_SHIFT;
+ boolean_t restarted = B_FALSE;
+ uint64_t *cpuobj = NULL;
+ int dnodes_per_chunk = 1 << dmu_object_alloc_chunk_shift;
+ int error;
+
+ kpreempt_disable();
+ cpuobj = &os->os_obj_next_percpu[CPU_SEQID %
+ os->os_obj_next_percpu_len];
+ kpreempt_enable();
- mutex_enter(&os->os_obj_lock);
+ if (dn_slots == 0) {
+ dn_slots = DNODE_MIN_SLOTS;
+ } else {
+ ASSERT3S(dn_slots, >=, DNODE_MIN_SLOTS);
+ ASSERT3S(dn_slots, <=, DNODE_MAX_SLOTS);
+ }
+
+ /*
+ * The "chunk" of dnodes that is assigned to a CPU-specific
+ * allocator needs to be at least one block's worth, to avoid
+ * lock contention on the dbuf. It can be at most one L1 block's
+ * worth, so that the "rescan after polishing off a L1's worth"
+ * logic below will be sure to kick in.
+ */
+ if (dnodes_per_chunk < DNODES_PER_BLOCK)
+ dnodes_per_chunk = DNODES_PER_BLOCK;
+ if (dnodes_per_chunk > L1_dnode_count)
+ dnodes_per_chunk = L1_dnode_count;
+
+ object = *cpuobj;
for (;;) {
- object = os->os_obj_next;
/*
- * Each time we polish off an L2 bp worth of dnodes
- * (2^13 objects), move to another L2 bp that's still
- * reasonably sparse (at most 1/4 full). Look from the
- * beginning once, but after that keep looking from here.
- * If we can't find one, just keep going from here.
- *
- * Note that dmu_traverse depends on the behavior that we use
- * multiple blocks of the dnode object before going back to
- * reuse objects. Any change to this algorithm should preserve
- * that property or find another solution to the issues
- * described in traverse_visitbp.
+ * If we finished a chunk of dnodes, get a new one from
+ * the global allocator.
*/
- if (P2PHASE(object, L2_dnode_count) == 0) {
- uint64_t offset = restarted ? object << DNODE_SHIFT : 0;
- int error = dnode_next_offset(DMU_META_DNODE(os),
- DNODE_FIND_HOLE,
- &offset, 2, DNODES_PER_BLOCK >> 2, 0);
- restarted = B_TRUE;
- if (error == 0)
- object = offset >> DNODE_SHIFT;
+ if ((P2PHASE(object, dnodes_per_chunk) == 0) ||
+ (P2PHASE(object + dn_slots - 1, dnodes_per_chunk) <
+ dn_slots)) {
+ DNODE_STAT_BUMP(dnode_alloc_next_chunk);
+ mutex_enter(&os->os_obj_lock);
+ ASSERT0(P2PHASE(os->os_obj_next_chunk,
+ dnodes_per_chunk));
+ object = os->os_obj_next_chunk;
+
+ /*
+ * Each time we polish off a L1 bp worth of dnodes
+ * (2^12 objects), move to another L1 bp that's
+ * still reasonably sparse (at most 1/4 full). Look
+ * from the beginning at most once per txg. If we
+ * still can't allocate from that L1 block, search
+ * for an empty L0 block, which will quickly skip
+ * to the end of the metadnode if no nearby L0
+ * blocks are empty. This fallback avoids a
+ * pathology where full dnode blocks containing
+ * large dnodes appear sparse because they have a
+ * low blk_fill, leading to many failed allocation
+ * attempts. In the long term a better mechanism to
+ * search for sparse metadnode regions, such as
+ * spacemaps, could be implemented.
+ *
+ * os_scan_dnodes is set during txg sync if enough
+ * objects have been freed since the previous
+ * rescan to justify backfilling again.
+ *
+ * Note that dmu_traverse depends on the behavior
+ * that we use multiple blocks of the dnode object
+ * before going back to reuse objects. Any change
+ * to this algorithm should preserve that property
+ * or find another solution to the issues described
+ * in traverse_visitbp.
+ */
+ if (P2PHASE(object, L1_dnode_count) == 0) {
+ uint64_t offset;
+ uint64_t blkfill;
+ int minlvl;
+ if (os->os_rescan_dnodes) {
+ offset = 0;
+ os->os_rescan_dnodes = B_FALSE;
+ } else {
+ offset = object << DNODE_SHIFT;
+ }
+ blkfill = restarted ? 1 : DNODES_PER_BLOCK >> 2;
+ minlvl = restarted ? 1 : 2;
+ restarted = B_TRUE;
+ error = dnode_next_offset(DMU_META_DNODE(os),
+ DNODE_FIND_HOLE, &offset, minlvl,
+ blkfill, 0);
+ if (error == 0) {
+ object = offset >> DNODE_SHIFT;
+ }
+ }
+ /*
+ * Note: if "restarted", we may find a L0 that
+ * is not suitably aligned.
+ */
+ os->os_obj_next_chunk =
+ P2ALIGN(object, dnodes_per_chunk) +
+ dnodes_per_chunk;
+ (void) atomic_swap_64(cpuobj, object);
+ mutex_exit(&os->os_obj_lock);
}
- os->os_obj_next = ++object;
+
+ /*
+ * The value of (*cpuobj) before adding dn_slots is the object
+ * ID assigned to us. The value afterwards is the object ID
+ * assigned to whoever wants to do an allocation next.
+ */
+ object = atomic_add_64_nv(cpuobj, dn_slots) - dn_slots;
/*
* XXX We should check for an i/o error here and return
* dmu_tx_assign(), but there is currently no mechanism
* to do so.
*/
- (void) dnode_hold_impl(os, object, DNODE_MUST_BE_FREE,
- FTAG, &dn);
- if (dn)
- break;
+ error = dnode_hold_impl(os, object, DNODE_MUST_BE_FREE,
+ dn_slots, FTAG, &dn);
+ if (error == 0) {
+ rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
+ /*
+ * Another thread could have allocated it; check
+ * again now that we have the struct lock.
+ */
+ if (dn->dn_type == DMU_OT_NONE) {
+ dnode_allocate(dn, ot, blocksize, 0,
+ bonustype, bonuslen, dn_slots, tx);
+ rw_exit(&dn->dn_struct_rwlock);
+ dmu_tx_add_new_object(tx, dn);
+ dnode_rele(dn, FTAG);
+ return (object);
+ }
+ rw_exit(&dn->dn_struct_rwlock);
+ dnode_rele(dn, FTAG);
+ DNODE_STAT_BUMP(dnode_alloc_race);
+ }
- if (dmu_object_next(os, &object, B_TRUE, 0) == 0)
- os->os_obj_next = object - 1;
+ /*
+ * Skip to next known valid starting point on error. This
+ * is the start of the next block of dnodes.
+ */
+ if (dmu_object_next(os, &object, B_TRUE, 0) != 0) {
+ object = P2ROUNDUP(object + 1, DNODES_PER_BLOCK);
+ DNODE_STAT_BUMP(dnode_alloc_next_block);
+ }
+ (void) atomic_swap_64(cpuobj, object);
}
-
- dnode_allocate(dn, ot, blocksize, 0, bonustype, bonuslen, tx);
- dnode_rele(dn, FTAG);
-
- mutex_exit(&os->os_obj_lock);
-
- dmu_tx_add_new_object(tx, os, object);
- return (object);
}
int
dmu_object_claim(objset_t *os, uint64_t object, dmu_object_type_t ot,
int blocksize, dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
+{
+ return (dmu_object_claim_dnsize(os, object, ot, blocksize, bonustype,
+ bonuslen, 0, tx));
+}
+
+int
+dmu_object_claim_dnsize(objset_t *os, uint64_t object, dmu_object_type_t ot,
+ int blocksize, dmu_object_type_t bonustype, int bonuslen,
+ int dnodesize, dmu_tx_t *tx)
{
dnode_t *dn;
+ int dn_slots = dnodesize >> DNODE_SHIFT;
int err;
+ if (dn_slots == 0)
+ dn_slots = DNODE_MIN_SLOTS;
+ ASSERT3S(dn_slots, >=, DNODE_MIN_SLOTS);
+ ASSERT3S(dn_slots, <=, DNODE_MAX_SLOTS);
+
if (object == DMU_META_DNODE_OBJECT && !dmu_tx_private_ok(tx))
return (SET_ERROR(EBADF));
- err = dnode_hold_impl(os, object, DNODE_MUST_BE_FREE, FTAG, &dn);
+ err = dnode_hold_impl(os, object, DNODE_MUST_BE_FREE, dn_slots,
+ FTAG, &dn);
if (err)
return (err);
- dnode_allocate(dn, ot, blocksize, 0, bonustype, bonuslen, tx);
+
+ dnode_allocate(dn, ot, blocksize, 0, bonustype, bonuslen, dn_slots, tx);
+ dmu_tx_add_new_object(tx, dn);
+
dnode_rele(dn, FTAG);
- dmu_tx_add_new_object(tx, os, object);
return (0);
}
int
dmu_object_reclaim(objset_t *os, uint64_t object, dmu_object_type_t ot,
int blocksize, dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
+{
+ return (dmu_object_reclaim_dnsize(os, object, ot, blocksize, bonustype,
+ bonuslen, 0, tx));
+}
+
+int
+dmu_object_reclaim_dnsize(objset_t *os, uint64_t object, dmu_object_type_t ot,
+ int blocksize, dmu_object_type_t bonustype, int bonuslen, int dnodesize,
+ dmu_tx_t *tx)
{
dnode_t *dn;
+ int dn_slots = dnodesize >> DNODE_SHIFT;
int err;
if (object == DMU_META_DNODE_OBJECT)
return (SET_ERROR(EBADF));
- err = dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED,
+ err = dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED, 0,
FTAG, &dn);
if (err)
return (err);
- dnode_reallocate(dn, ot, blocksize, bonustype, bonuslen, tx);
+ dnode_reallocate(dn, ot, blocksize, bonustype, bonuslen, dn_slots, tx);
dnode_rele(dn, FTAG);
return (err);
}
+
int
dmu_object_free(objset_t *os, uint64_t object, dmu_tx_t *tx)
{
ASSERT(object != DMU_META_DNODE_OBJECT || dmu_tx_private_ok(tx));
- err = dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED,
+ err = dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED, 0,
FTAG, &dn);
if (err)
return (err);
return (0);
}
+/*
+ * Return (in *objectp) the next object which is allocated (or a hole)
+ * after *object, taking into account only objects that may have been modified
+ * after the specified txg.
+ */
int
dmu_object_next(objset_t *os, uint64_t *objectp, boolean_t hole, uint64_t txg)
{
- uint64_t offset = (*objectp + 1) << DNODE_SHIFT;
+ uint64_t offset;
+ uint64_t start_obj;
+ struct dsl_dataset *ds = os->os_dsl_dataset;
int error;
+ if (*objectp == 0) {
+ start_obj = 1;
+ } else if (ds && ds->ds_feature_inuse[SPA_FEATURE_LARGE_DNODE]) {
+ uint64_t i = *objectp + 1;
+ uint64_t last_obj = *objectp | (DNODES_PER_BLOCK - 1);
+ dmu_object_info_t doi;
+
+ /*
+ * Scan through the remaining meta dnode block. The contents
+ * of each slot in the block are known so it can be quickly
+ * checked. If the block is exhausted without a match then
+ * hand off to dnode_next_offset() for further scanning.
+ */
+ while (i <= last_obj) {
+ error = dmu_object_info(os, i, &doi);
+ if (error == ENOENT) {
+ if (hole) {
+ *objectp = i;
+ return (0);
+ } else {
+ i++;
+ }
+ } else if (error == EEXIST) {
+ i++;
+ } else if (error == 0) {
+ if (hole) {
+ i += doi.doi_dnodesize >> DNODE_SHIFT;
+ } else {
+ *objectp = i;
+ return (0);
+ }
+ } else {
+ return (error);
+ }
+ }
+
+ start_obj = i;
+ } else {
+ start_obj = *objectp + 1;
+ }
+
+ offset = start_obj << DNODE_SHIFT;
+
error = dnode_next_offset(DMU_META_DNODE(os),
(hole ? DNODE_FIND_HOLE : 0), &offset, 0, DNODES_PER_BLOCK, txg);
#if defined(_KERNEL) && defined(HAVE_SPL)
EXPORT_SYMBOL(dmu_object_alloc);
+EXPORT_SYMBOL(dmu_object_alloc_dnsize);
EXPORT_SYMBOL(dmu_object_claim);
+EXPORT_SYMBOL(dmu_object_claim_dnsize);
EXPORT_SYMBOL(dmu_object_reclaim);
+EXPORT_SYMBOL(dmu_object_reclaim_dnsize);
EXPORT_SYMBOL(dmu_object_free);
EXPORT_SYMBOL(dmu_object_next);
EXPORT_SYMBOL(dmu_object_zapify);
EXPORT_SYMBOL(dmu_object_free_zapified);
+
+/* BEGIN CSTYLED */
+module_param(dmu_object_alloc_chunk_shift, int, 0644);
+MODULE_PARM_DESC(dmu_object_alloc_chunk_shift,
+ "CPU-specific allocator grabs 2^N objects at once");
+/* END CSTYLED */
#endif
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