4 * Userspace RCU library - Lock-Free Resizable RCU Hash Table
6 * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 * Based on the following articles:
26 * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free
27 * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405.
28 * - Michael, M. M. High performance dynamic lock-free hash tables
29 * and list-based sets. In Proceedings of the fourteenth annual ACM
30 * symposium on Parallel algorithms and architectures, ACM Press,
33 * Some specificities of this Lock-Free Resizable RCU Hash Table
36 * - RCU read-side critical section allows readers to perform hash
37 * table lookups and use the returned objects safely by delaying
38 * memory reclaim of a grace period.
39 * - Add and remove operations are lock-free, and do not need to
40 * allocate memory. They need to be executed within RCU read-side
41 * critical section to ensure the objects they read are valid and to
42 * deal with the cmpxchg ABA problem.
43 * - add and add_unique operations are supported. add_unique checks if
44 * the node key already exists in the hash table. It ensures no key
46 * - The resize operation executes concurrently with add/remove/lookup.
47 * - Hash table nodes are contained within a split-ordered list. This
48 * list is ordered by incrementing reversed-bits-hash value.
49 * - An index of bucket nodes is kept. These bucket nodes are the hash
50 * table "buckets", and they are also chained together in the
51 * split-ordered list, which allows recursive expansion.
52 * - The resize operation for small tables only allows expanding the hash table.
53 * It is triggered automatically by detecting long chains in the add
55 * - The resize operation for larger tables (and available through an
56 * API) allows both expanding and shrinking the hash table.
57 * - Split-counters are used to keep track of the number of
58 * nodes within the hash table for automatic resize triggering.
59 * - Resize operation initiated by long chain detection is executed by a
60 * call_rcu thread, which keeps lock-freedom of add and remove.
61 * - Resize operations are protected by a mutex.
62 * - The removal operation is split in two parts: first, a "removed"
63 * flag is set in the next pointer within the node to remove. Then,
64 * a "garbage collection" is performed in the bucket containing the
65 * removed node (from the start of the bucket up to the removed node).
66 * All encountered nodes with "removed" flag set in their next
67 * pointers are removed from the linked-list. If the cmpxchg used for
68 * removal fails (due to concurrent garbage-collection or concurrent
69 * add), we retry from the beginning of the bucket. This ensures that
70 * the node with "removed" flag set is removed from the hash table
71 * (not visible to lookups anymore) before the RCU read-side critical
72 * section held across removal ends. Furthermore, this ensures that
73 * the node with "removed" flag set is removed from the linked-list
74 * before its memory is reclaimed. Only the thread which removal
75 * successfully set the "removed" flag (with a cmpxchg) into a node's
76 * next pointer is considered to have succeeded its removal (and thus
77 * owns the node to reclaim). Because we garbage-collect starting from
78 * an invariant node (the start-of-bucket bucket node) up to the
79 * "removed" node (or find a reverse-hash that is higher), we are sure
80 * that a successful traversal of the chain leads to a chain that is
81 * present in the linked-list (the start node is never removed) and
82 * that is does not contain the "removed" node anymore, even if
83 * concurrent delete/add operations are changing the structure of the
85 * - The add operation performs gargage collection of buckets if it
86 * encounters nodes with removed flag set in the bucket where it wants
87 * to add its new node. This ensures lock-freedom of add operation by
88 * helping the remover unlink nodes from the list rather than to wait
90 * - A RCU "order table" indexed by log2(hash index) is copied and
91 * expanded by the resize operation. This order table allows finding
92 * the "bucket node" tables.
93 * - There is one bucket node table per hash index order. The size of
94 * each bucket node table is half the number of hashes contained in
95 * this order (except for order 0).
96 * - synchronzie_rcu is used to garbage-collect the old bucket node table.
97 * - The per-order bucket node tables contain a compact version of the
98 * hash table nodes. These tables are invariant after they are
99 * populated into the hash table.
101 * Bucket node tables:
103 * hash table hash table the last all bucket node tables
104 * order size bucket node 0 1 2 3 4 5 6(index)
111 * 5 32 16 1 1 2 4 8 16
112 * 6 64 32 1 1 2 4 8 16 32
114 * When growing/shrinking, we only focus on the last bucket node table
115 * which size is (!order ? 1 : (1 << (order -1))).
117 * Example for growing/shrinking:
118 * grow hash table from order 5 to 6: init the index=6 bucket node table
119 * shrink hash table from order 6 to 5: fini the index=6 bucket node table
121 * A bit of ascii art explanation:
123 * Order index is the off-by-one compare to the actual power of 2 because
124 * we use index 0 to deal with the 0 special-case.
126 * This shows the nodes for a small table ordered by reversed bits:
138 * This shows the nodes in order of non-reversed bits, linked by
139 * reversed-bit order.
144 * 2 | | 2 010 010 <- |
145 * | | | 3 011 110 | <- |
146 * 3 -> | | | 4 100 001 | |
162 #include <urcu-call-rcu.h>
163 #include <urcu-flavor.h>
164 #include <urcu/arch.h>
165 #include <urcu/uatomic.h>
166 #include <urcu/compiler.h>
167 #include <urcu/rculfhash.h>
168 #include <rculfhash-internal.h>
173 * Split-counters lazily update the global counter each 1024
174 * addition/removal. It automatically keeps track of resize required.
175 * We use the bucket length as indicator for need to expand for small
176 * tables and machines lacking per-cpu data suppport.
178 #define COUNT_COMMIT_ORDER 10
179 #define DEFAULT_SPLIT_COUNT_MASK 0xFUL
180 #define CHAIN_LEN_TARGET 1
181 #define CHAIN_LEN_RESIZE_THRESHOLD 3
184 * Define the minimum table size.
186 #define MIN_TABLE_ORDER 0
187 #define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
190 * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
192 #define MIN_PARTITION_PER_THREAD_ORDER 12
193 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
196 * The removed flag needs to be updated atomically with the pointer.
197 * It indicates that no node must attach to the node scheduled for
198 * removal, and that node garbage collection must be performed.
199 * The bucket flag does not require to be updated atomically with the
200 * pointer, but it is added as a pointer low bit flag to save space.
202 #define REMOVED_FLAG (1UL << 0)
203 #define BUCKET_FLAG (1UL << 1)
204 #define FLAGS_MASK ((1UL << 2) - 1)
206 /* Value of the end pointer. Should not interact with flags. */
207 #define END_VALUE NULL
210 * ht_items_count: Split-counters counting the number of node addition
211 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
212 * is set at hash table creation.
214 * These are free-running counters, never reset to zero. They count the
215 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
216 * operations to update the global counter. We choose a power-of-2 value
217 * for the trigger to deal with 32 or 64-bit overflow of the counter.
219 struct ht_items_count
{
220 unsigned long add
, del
;
221 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
224 * rcu_resize_work: Contains arguments passed to RCU worker thread
225 * responsible for performing lazy resize.
227 struct rcu_resize_work
{
228 struct rcu_head head
;
233 * partition_resize_work: Contains arguments passed to worker threads
234 * executing the hash table resize on partitions of the hash table
235 * assigned to each processor's worker thread.
237 struct partition_resize_work
{
240 unsigned long i
, start
, len
;
241 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
242 unsigned long start
, unsigned long len
);
246 void _cds_lfht_add(struct cds_lfht
*ht
,
247 cds_lfht_match_fct match
,
250 struct cds_lfht_node
*node
,
251 struct cds_lfht_iter
*unique_ret
,
255 * Algorithm to reverse bits in a word by lookup table, extended to
258 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
259 * Originally from Public Domain.
262 static const uint8_t BitReverseTable256
[256] =
264 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
265 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
266 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
267 R6(0), R6(2), R6(1), R6(3)
274 uint8_t bit_reverse_u8(uint8_t v
)
276 return BitReverseTable256
[v
];
279 static __attribute__((unused
))
280 uint32_t bit_reverse_u32(uint32_t v
)
282 return ((uint32_t) bit_reverse_u8(v
) << 24) |
283 ((uint32_t) bit_reverse_u8(v
>> 8) << 16) |
284 ((uint32_t) bit_reverse_u8(v
>> 16) << 8) |
285 ((uint32_t) bit_reverse_u8(v
>> 24));
288 static __attribute__((unused
))
289 uint64_t bit_reverse_u64(uint64_t v
)
291 return ((uint64_t) bit_reverse_u8(v
) << 56) |
292 ((uint64_t) bit_reverse_u8(v
>> 8) << 48) |
293 ((uint64_t) bit_reverse_u8(v
>> 16) << 40) |
294 ((uint64_t) bit_reverse_u8(v
>> 24) << 32) |
295 ((uint64_t) bit_reverse_u8(v
>> 32) << 24) |
296 ((uint64_t) bit_reverse_u8(v
>> 40) << 16) |
297 ((uint64_t) bit_reverse_u8(v
>> 48) << 8) |
298 ((uint64_t) bit_reverse_u8(v
>> 56));
302 unsigned long bit_reverse_ulong(unsigned long v
)
304 #if (CAA_BITS_PER_LONG == 32)
305 return bit_reverse_u32(v
);
307 return bit_reverse_u64(v
);
312 * fls: returns the position of the most significant bit.
313 * Returns 0 if no bit is set, else returns the position of the most
314 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
316 #if defined(__i386) || defined(__x86_64)
318 unsigned int fls_u32(uint32_t x
)
326 : "=r" (r
) : "rm" (x
));
332 #if defined(__x86_64)
334 unsigned int fls_u64(uint64_t x
)
342 : "=r" (r
) : "rm" (x
));
349 static __attribute__((unused
))
350 unsigned int fls_u64(uint64_t x
)
357 if (!(x
& 0xFFFFFFFF00000000ULL
)) {
361 if (!(x
& 0xFFFF000000000000ULL
)) {
365 if (!(x
& 0xFF00000000000000ULL
)) {
369 if (!(x
& 0xF000000000000000ULL
)) {
373 if (!(x
& 0xC000000000000000ULL
)) {
377 if (!(x
& 0x8000000000000000ULL
)) {
386 static __attribute__((unused
))
387 unsigned int fls_u32(uint32_t x
)
393 if (!(x
& 0xFFFF0000U
)) {
397 if (!(x
& 0xFF000000U
)) {
401 if (!(x
& 0xF0000000U
)) {
405 if (!(x
& 0xC0000000U
)) {
409 if (!(x
& 0x80000000U
)) {
417 unsigned int fls_ulong(unsigned long x
)
419 #if (CAA_BITS_PER_LONG == 32)
427 * Return the minimum order for which x <= (1UL << order).
428 * Return -1 if x is 0.
430 int get_count_order_u32(uint32_t x
)
435 return fls_u32(x
- 1);
439 * Return the minimum order for which x <= (1UL << order).
440 * Return -1 if x is 0.
442 int get_count_order_ulong(unsigned long x
)
447 return fls_ulong(x
- 1);
451 void cds_lfht_resize_lazy_grow(struct cds_lfht
*ht
, unsigned long size
, int growth
);
454 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
455 unsigned long count
);
457 static long nr_cpus_mask
= -1;
458 static long split_count_mask
= -1;
460 #if defined(HAVE_SYSCONF)
461 static void ht_init_nr_cpus_mask(void)
465 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
471 * round up number of CPUs to next power of two, so we
472 * can use & for modulo.
474 maxcpus
= 1UL << get_count_order_ulong(maxcpus
);
475 nr_cpus_mask
= maxcpus
- 1;
477 #else /* #if defined(HAVE_SYSCONF) */
478 static void ht_init_nr_cpus_mask(void)
482 #endif /* #else #if defined(HAVE_SYSCONF) */
485 void alloc_split_items_count(struct cds_lfht
*ht
)
487 struct ht_items_count
*count
;
489 if (nr_cpus_mask
== -1) {
490 ht_init_nr_cpus_mask();
491 if (nr_cpus_mask
< 0)
492 split_count_mask
= DEFAULT_SPLIT_COUNT_MASK
;
494 split_count_mask
= nr_cpus_mask
;
497 assert(split_count_mask
>= 0);
499 if (ht
->flags
& CDS_LFHT_ACCOUNTING
) {
500 ht
->split_count
= calloc(split_count_mask
+ 1, sizeof(*count
));
501 assert(ht
->split_count
);
503 ht
->split_count
= NULL
;
508 void free_split_items_count(struct cds_lfht
*ht
)
510 poison_free(ht
->split_count
);
513 #if defined(HAVE_SCHED_GETCPU)
515 int ht_get_split_count_index(unsigned long hash
)
519 assert(split_count_mask
>= 0);
520 cpu
= sched_getcpu();
521 if (caa_unlikely(cpu
< 0))
522 return hash
& split_count_mask
;
524 return cpu
& split_count_mask
;
526 #else /* #if defined(HAVE_SCHED_GETCPU) */
528 int ht_get_split_count_index(unsigned long hash
)
530 return hash
& split_count_mask
;
532 #endif /* #else #if defined(HAVE_SCHED_GETCPU) */
535 void ht_count_add(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
537 unsigned long split_count
;
541 if (caa_unlikely(!ht
->split_count
))
543 index
= ht_get_split_count_index(hash
);
544 split_count
= uatomic_add_return(&ht
->split_count
[index
].add
, 1);
545 if (caa_likely(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))
547 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
549 dbg_printf("add split count %lu\n", split_count
);
550 count
= uatomic_add_return(&ht
->count
,
551 1UL << COUNT_COMMIT_ORDER
);
552 if (caa_likely(count
& (count
- 1)))
554 /* Only if global count is power of 2 */
556 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) < size
)
558 dbg_printf("add set global %ld\n", count
);
559 cds_lfht_resize_lazy_count(ht
, size
,
560 count
>> (CHAIN_LEN_TARGET
- 1));
564 void ht_count_del(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
566 unsigned long split_count
;
570 if (caa_unlikely(!ht
->split_count
))
572 index
= ht_get_split_count_index(hash
);
573 split_count
= uatomic_add_return(&ht
->split_count
[index
].del
, 1);
574 if (caa_likely(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))
576 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
578 dbg_printf("del split count %lu\n", split_count
);
579 count
= uatomic_add_return(&ht
->count
,
580 -(1UL << COUNT_COMMIT_ORDER
));
581 if (caa_likely(count
& (count
- 1)))
583 /* Only if global count is power of 2 */
585 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) >= size
)
587 dbg_printf("del set global %ld\n", count
);
589 * Don't shrink table if the number of nodes is below a
592 if (count
< (1UL << COUNT_COMMIT_ORDER
) * (split_count_mask
+ 1))
594 cds_lfht_resize_lazy_count(ht
, size
,
595 count
>> (CHAIN_LEN_TARGET
- 1));
599 void check_resize(struct cds_lfht
*ht
, unsigned long size
, uint32_t chain_len
)
603 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
605 count
= uatomic_read(&ht
->count
);
607 * Use bucket-local length for small table expand and for
608 * environments lacking per-cpu data support.
610 if (count
>= (1UL << COUNT_COMMIT_ORDER
))
613 dbg_printf("WARNING: large chain length: %u.\n",
615 if (chain_len
>= CHAIN_LEN_RESIZE_THRESHOLD
)
616 cds_lfht_resize_lazy_grow(ht
, size
,
617 get_count_order_u32(chain_len
- (CHAIN_LEN_TARGET
- 1)));
621 struct cds_lfht_node
*clear_flag(struct cds_lfht_node
*node
)
623 return (struct cds_lfht_node
*) (((unsigned long) node
) & ~FLAGS_MASK
);
627 int is_removed(struct cds_lfht_node
*node
)
629 return ((unsigned long) node
) & REMOVED_FLAG
;
633 struct cds_lfht_node
*flag_removed(struct cds_lfht_node
*node
)
635 return (struct cds_lfht_node
*) (((unsigned long) node
) | REMOVED_FLAG
);
639 int is_bucket(struct cds_lfht_node
*node
)
641 return ((unsigned long) node
) & BUCKET_FLAG
;
645 struct cds_lfht_node
*flag_bucket(struct cds_lfht_node
*node
)
647 return (struct cds_lfht_node
*) (((unsigned long) node
) | BUCKET_FLAG
);
651 struct cds_lfht_node
*get_end(void)
653 return (struct cds_lfht_node
*) END_VALUE
;
657 int is_end(struct cds_lfht_node
*node
)
659 return clear_flag(node
) == (struct cds_lfht_node
*) END_VALUE
;
663 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr
,
666 unsigned long old1
, old2
;
668 old1
= uatomic_read(ptr
);
673 } while ((old1
= uatomic_cmpxchg(ptr
, old2
, v
)) != old2
);
678 void cds_lfht_alloc_bucket_table(struct cds_lfht
*ht
, unsigned long order
)
680 return ht
->mm
->alloc_bucket_table(ht
, order
);
684 * cds_lfht_free_bucket_table() should be called with decreasing order.
685 * When cds_lfht_free_bucket_table(0) is called, it means the whole
689 void cds_lfht_free_bucket_table(struct cds_lfht
*ht
, unsigned long order
)
691 return ht
->mm
->free_bucket_table(ht
, order
);
695 struct cds_lfht_node
*bucket_at(struct cds_lfht
*ht
, unsigned long index
)
697 return ht
->bucket_at(ht
, index
);
701 struct cds_lfht_node
*lookup_bucket(struct cds_lfht
*ht
, unsigned long size
,
705 return bucket_at(ht
, hash
& (size
- 1));
709 * Remove all logically deleted nodes from a bucket up to a certain node key.
712 void _cds_lfht_gc_bucket(struct cds_lfht_node
*bucket
, struct cds_lfht_node
*node
)
714 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_next
;
716 assert(!is_bucket(bucket
));
717 assert(!is_removed(bucket
));
718 assert(!is_bucket(node
));
719 assert(!is_removed(node
));
722 /* We can always skip the bucket node initially */
723 iter
= rcu_dereference(iter_prev
->next
);
724 assert(!is_removed(iter
));
725 assert(iter_prev
->reverse_hash
<= node
->reverse_hash
);
727 * We should never be called with bucket (start of chain)
728 * and logically removed node (end of path compression
729 * marker) being the actual same node. This would be a
730 * bug in the algorithm implementation.
732 assert(bucket
!= node
);
734 if (caa_unlikely(is_end(iter
)))
736 if (caa_likely(clear_flag(iter
)->reverse_hash
> node
->reverse_hash
))
738 next
= rcu_dereference(clear_flag(iter
)->next
);
739 if (caa_likely(is_removed(next
)))
741 iter_prev
= clear_flag(iter
);
744 assert(!is_removed(iter
));
746 new_next
= flag_bucket(clear_flag(next
));
748 new_next
= clear_flag(next
);
749 (void) uatomic_cmpxchg(&iter_prev
->next
, iter
, new_next
);
755 int _cds_lfht_replace(struct cds_lfht
*ht
, unsigned long size
,
756 struct cds_lfht_node
*old_node
,
757 struct cds_lfht_node
*old_next
,
758 struct cds_lfht_node
*new_node
)
760 struct cds_lfht_node
*bucket
, *ret_next
;
762 if (!old_node
) /* Return -ENOENT if asked to replace NULL node */
765 assert(!is_removed(old_node
));
766 assert(!is_bucket(old_node
));
767 assert(!is_removed(new_node
));
768 assert(!is_bucket(new_node
));
769 assert(new_node
!= old_node
);
771 /* Insert after node to be replaced */
772 if (is_removed(old_next
)) {
774 * Too late, the old node has been removed under us
775 * between lookup and replace. Fail.
779 assert(!is_bucket(old_next
));
780 assert(new_node
!= clear_flag(old_next
));
781 new_node
->next
= clear_flag(old_next
);
783 * Here is the whole trick for lock-free replace: we add
784 * the replacement node _after_ the node we want to
785 * replace by atomically setting its next pointer at the
786 * same time we set its removal flag. Given that
787 * the lookups/get next use an iterator aware of the
788 * next pointer, they will either skip the old node due
789 * to the removal flag and see the new node, or use
790 * the old node, but will not see the new one.
792 ret_next
= uatomic_cmpxchg(&old_node
->next
,
793 old_next
, flag_removed(new_node
));
794 if (ret_next
== old_next
)
795 break; /* We performed the replacement. */
800 * Ensure that the old node is not visible to readers anymore:
801 * lookup for the node, and remove it (along with any other
802 * logically removed node) if found.
804 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(old_node
->reverse_hash
));
805 _cds_lfht_gc_bucket(bucket
, new_node
);
807 assert(is_removed(rcu_dereference(old_node
->next
)));
812 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
813 * mode. A NULL unique_ret allows creation of duplicate keys.
816 void _cds_lfht_add(struct cds_lfht
*ht
,
817 cds_lfht_match_fct match
,
820 struct cds_lfht_node
*node
,
821 struct cds_lfht_iter
*unique_ret
,
824 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_node
, *new_next
,
826 struct cds_lfht_node
*bucket
;
828 assert(!is_bucket(node
));
829 assert(!is_removed(node
));
830 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->reverse_hash
));
832 uint32_t chain_len
= 0;
835 * iter_prev points to the non-removed node prior to the
839 /* We can always skip the bucket node initially */
840 iter
= rcu_dereference(iter_prev
->next
);
841 assert(iter_prev
->reverse_hash
<= node
->reverse_hash
);
843 if (caa_unlikely(is_end(iter
)))
845 if (caa_likely(clear_flag(iter
)->reverse_hash
> node
->reverse_hash
))
848 /* bucket node is the first node of the identical-hash-value chain */
849 if (bucket_flag
&& clear_flag(iter
)->reverse_hash
== node
->reverse_hash
)
852 next
= rcu_dereference(clear_flag(iter
)->next
);
853 if (caa_unlikely(is_removed(next
)))
859 && clear_flag(iter
)->reverse_hash
== node
->reverse_hash
) {
860 struct cds_lfht_iter d_iter
= { .node
= node
, .next
= iter
, };
863 * uniquely adding inserts the node as the first
864 * node of the identical-hash-value node chain.
866 * This semantic ensures no duplicated keys
867 * should ever be observable in the table
868 * (including observe one node by one node
869 * by forward iterations)
871 cds_lfht_next_duplicate(ht
, match
, key
, &d_iter
);
875 *unique_ret
= d_iter
;
879 /* Only account for identical reverse hash once */
880 if (iter_prev
->reverse_hash
!= clear_flag(iter
)->reverse_hash
882 check_resize(ht
, size
, ++chain_len
);
883 iter_prev
= clear_flag(iter
);
888 assert(node
!= clear_flag(iter
));
889 assert(!is_removed(iter_prev
));
890 assert(!is_removed(iter
));
891 assert(iter_prev
!= node
);
893 node
->next
= clear_flag(iter
);
895 node
->next
= flag_bucket(clear_flag(iter
));
897 new_node
= flag_bucket(node
);
900 if (uatomic_cmpxchg(&iter_prev
->next
, iter
,
902 continue; /* retry */
909 assert(!is_removed(iter
));
911 new_next
= flag_bucket(clear_flag(next
));
913 new_next
= clear_flag(next
);
914 (void) uatomic_cmpxchg(&iter_prev
->next
, iter
, new_next
);
919 unique_ret
->node
= return_node
;
920 /* unique_ret->next left unset, never used. */
925 int _cds_lfht_del(struct cds_lfht
*ht
, unsigned long size
,
926 struct cds_lfht_node
*node
,
929 struct cds_lfht_node
*bucket
, *next
, *old
;
931 if (!node
) /* Return -ENOENT if asked to delete NULL node */
934 /* logically delete the node */
935 assert(!is_bucket(node
));
936 assert(!is_removed(node
));
937 old
= rcu_dereference(node
->next
);
939 struct cds_lfht_node
*new_next
;
942 if (caa_unlikely(is_removed(next
)))
945 assert(is_bucket(next
));
947 assert(!is_bucket(next
));
948 new_next
= flag_removed(next
);
949 old
= uatomic_cmpxchg(&node
->next
, next
, new_next
);
950 } while (old
!= next
);
951 /* We performed the (logical) deletion. */
954 * Ensure that the node is not visible to readers anymore: lookup for
955 * the node, and remove it (along with any other logically removed node)
958 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->reverse_hash
));
959 _cds_lfht_gc_bucket(bucket
, node
);
961 assert(is_removed(rcu_dereference(node
->next
)));
966 void *partition_resize_thread(void *arg
)
968 struct partition_resize_work
*work
= arg
;
970 work
->ht
->flavor
->register_thread();
971 work
->fct(work
->ht
, work
->i
, work
->start
, work
->len
);
972 work
->ht
->flavor
->unregister_thread();
977 void partition_resize_helper(struct cds_lfht
*ht
, unsigned long i
,
979 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
980 unsigned long start
, unsigned long len
))
982 unsigned long partition_len
;
983 struct partition_resize_work
*work
;
985 unsigned long nr_threads
;
988 * Note: nr_cpus_mask + 1 is always power of 2.
989 * We spawn just the number of threads we need to satisfy the minimum
990 * partition size, up to the number of CPUs in the system.
992 if (nr_cpus_mask
> 0) {
993 nr_threads
= min(nr_cpus_mask
+ 1,
994 len
>> MIN_PARTITION_PER_THREAD_ORDER
);
998 partition_len
= len
>> get_count_order_ulong(nr_threads
);
999 work
= calloc(nr_threads
, sizeof(*work
));
1001 for (thread
= 0; thread
< nr_threads
; thread
++) {
1002 work
[thread
].ht
= ht
;
1004 work
[thread
].len
= partition_len
;
1005 work
[thread
].start
= thread
* partition_len
;
1006 work
[thread
].fct
= fct
;
1007 ret
= pthread_create(&(work
[thread
].thread_id
), ht
->resize_attr
,
1008 partition_resize_thread
, &work
[thread
]);
1011 for (thread
= 0; thread
< nr_threads
; thread
++) {
1012 ret
= pthread_join(work
[thread
].thread_id
, NULL
);
1019 * Holding RCU read lock to protect _cds_lfht_add against memory
1020 * reclaim that could be performed by other call_rcu worker threads (ABA
1023 * When we reach a certain length, we can split this population phase over
1024 * many worker threads, based on the number of CPUs available in the system.
1025 * This should therefore take care of not having the expand lagging behind too
1026 * many concurrent insertion threads by using the scheduler's ability to
1027 * schedule bucket node population fairly with insertions.
1030 void init_table_populate_partition(struct cds_lfht
*ht
, unsigned long i
,
1031 unsigned long start
, unsigned long len
)
1033 unsigned long j
, size
= 1UL << (i
- 1);
1035 assert(i
> MIN_TABLE_ORDER
);
1036 ht
->flavor
->read_lock();
1037 for (j
= size
+ start
; j
< size
+ start
+ len
; j
++) {
1038 struct cds_lfht_node
*new_node
= bucket_at(ht
, j
);
1040 assert(j
>= size
&& j
< (size
<< 1));
1041 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1043 new_node
->reverse_hash
= bit_reverse_ulong(j
);
1044 _cds_lfht_add(ht
, NULL
, NULL
, size
, new_node
, NULL
, 1);
1046 ht
->flavor
->read_unlock();
1050 void init_table_populate(struct cds_lfht
*ht
, unsigned long i
,
1053 assert(nr_cpus_mask
!= -1);
1054 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1055 ht
->flavor
->thread_online();
1056 init_table_populate_partition(ht
, i
, 0, len
);
1057 ht
->flavor
->thread_offline();
1060 partition_resize_helper(ht
, i
, len
, init_table_populate_partition
);
1064 void init_table(struct cds_lfht
*ht
,
1065 unsigned long first_order
, unsigned long last_order
)
1069 dbg_printf("init table: first_order %lu last_order %lu\n",
1070 first_order
, last_order
);
1071 assert(first_order
> MIN_TABLE_ORDER
);
1072 for (i
= first_order
; i
<= last_order
; i
++) {
1075 len
= 1UL << (i
- 1);
1076 dbg_printf("init order %lu len: %lu\n", i
, len
);
1078 /* Stop expand if the resize target changes under us */
1079 if (CMM_LOAD_SHARED(ht
->resize_target
) < (1UL << i
))
1082 cds_lfht_alloc_bucket_table(ht
, i
);
1085 * Set all bucket nodes reverse hash values for a level and
1086 * link all bucket nodes into the table.
1088 init_table_populate(ht
, i
, len
);
1091 * Update table size.
1093 cmm_smp_wmb(); /* populate data before RCU size */
1094 CMM_STORE_SHARED(ht
->size
, 1UL << i
);
1096 dbg_printf("init new size: %lu\n", 1UL << i
);
1097 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1103 * Holding RCU read lock to protect _cds_lfht_remove against memory
1104 * reclaim that could be performed by other call_rcu worker threads (ABA
1106 * For a single level, we logically remove and garbage collect each node.
1108 * As a design choice, we perform logical removal and garbage collection on a
1109 * node-per-node basis to simplify this algorithm. We also assume keeping good
1110 * cache locality of the operation would overweight possible performance gain
1111 * that could be achieved by batching garbage collection for multiple levels.
1112 * However, this would have to be justified by benchmarks.
1114 * Concurrent removal and add operations are helping us perform garbage
1115 * collection of logically removed nodes. We guarantee that all logically
1116 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1117 * invoked to free a hole level of bucket nodes (after a grace period).
1119 * Logical removal and garbage collection can therefore be done in batch or on a
1120 * node-per-node basis, as long as the guarantee above holds.
1122 * When we reach a certain length, we can split this removal over many worker
1123 * threads, based on the number of CPUs available in the system. This should
1124 * take care of not letting resize process lag behind too many concurrent
1125 * updater threads actively inserting into the hash table.
1128 void remove_table_partition(struct cds_lfht
*ht
, unsigned long i
,
1129 unsigned long start
, unsigned long len
)
1131 unsigned long j
, size
= 1UL << (i
- 1);
1133 assert(i
> MIN_TABLE_ORDER
);
1134 ht
->flavor
->read_lock();
1135 for (j
= size
+ start
; j
< size
+ start
+ len
; j
++) {
1136 struct cds_lfht_node
*fini_node
= bucket_at(ht
, j
);
1138 assert(j
>= size
&& j
< (size
<< 1));
1139 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1141 fini_node
->reverse_hash
= bit_reverse_ulong(j
);
1142 (void) _cds_lfht_del(ht
, size
, fini_node
, 1);
1144 ht
->flavor
->read_unlock();
1148 void remove_table(struct cds_lfht
*ht
, unsigned long i
, unsigned long len
)
1151 assert(nr_cpus_mask
!= -1);
1152 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1153 ht
->flavor
->thread_online();
1154 remove_table_partition(ht
, i
, 0, len
);
1155 ht
->flavor
->thread_offline();
1158 partition_resize_helper(ht
, i
, len
, remove_table_partition
);
1162 * fini_table() is never called for first_order == 0, which is why
1163 * free_by_rcu_order == 0 can be used as criterion to know if free must
1167 void fini_table(struct cds_lfht
*ht
,
1168 unsigned long first_order
, unsigned long last_order
)
1171 unsigned long free_by_rcu_order
= 0;
1173 dbg_printf("fini table: first_order %lu last_order %lu\n",
1174 first_order
, last_order
);
1175 assert(first_order
> MIN_TABLE_ORDER
);
1176 for (i
= last_order
; i
>= first_order
; i
--) {
1179 len
= 1UL << (i
- 1);
1180 dbg_printf("fini order %lu len: %lu\n", i
, len
);
1182 /* Stop shrink if the resize target changes under us */
1183 if (CMM_LOAD_SHARED(ht
->resize_target
) > (1UL << (i
- 1)))
1186 cmm_smp_wmb(); /* populate data before RCU size */
1187 CMM_STORE_SHARED(ht
->size
, 1UL << (i
- 1));
1190 * We need to wait for all add operations to reach Q.S. (and
1191 * thus use the new table for lookups) before we can start
1192 * releasing the old bucket nodes. Otherwise their lookup will
1193 * return a logically removed node as insert position.
1195 ht
->flavor
->update_synchronize_rcu();
1196 if (free_by_rcu_order
)
1197 cds_lfht_free_bucket_table(ht
, free_by_rcu_order
);
1200 * Set "removed" flag in bucket nodes about to be removed.
1201 * Unlink all now-logically-removed bucket node pointers.
1202 * Concurrent add/remove operation are helping us doing
1205 remove_table(ht
, i
, len
);
1207 free_by_rcu_order
= i
;
1209 dbg_printf("fini new size: %lu\n", 1UL << i
);
1210 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1214 if (free_by_rcu_order
) {
1215 ht
->flavor
->update_synchronize_rcu();
1216 cds_lfht_free_bucket_table(ht
, free_by_rcu_order
);
1221 void cds_lfht_create_bucket(struct cds_lfht
*ht
, unsigned long size
)
1223 struct cds_lfht_node
*prev
, *node
;
1224 unsigned long order
, len
, i
;
1226 cds_lfht_alloc_bucket_table(ht
, 0);
1228 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1229 node
= bucket_at(ht
, 0);
1230 node
->next
= flag_bucket(get_end());
1231 node
->reverse_hash
= 0;
1233 for (order
= 1; order
< get_count_order_ulong(size
) + 1; order
++) {
1234 len
= 1UL << (order
- 1);
1235 cds_lfht_alloc_bucket_table(ht
, order
);
1237 for (i
= 0; i
< len
; i
++) {
1239 * Now, we are trying to init the node with the
1240 * hash=(len+i) (which is also a bucket with the
1241 * index=(len+i)) and insert it into the hash table,
1242 * so this node has to be inserted after the bucket
1243 * with the index=(len+i)&(len-1)=i. And because there
1244 * is no other non-bucket node nor bucket node with
1245 * larger index/hash inserted, so the bucket node
1246 * being inserted should be inserted directly linked
1247 * after the bucket node with index=i.
1249 prev
= bucket_at(ht
, i
);
1250 node
= bucket_at(ht
, len
+ i
);
1252 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1253 order
, len
+ i
, len
+ i
);
1254 node
->reverse_hash
= bit_reverse_ulong(len
+ i
);
1256 /* insert after prev */
1257 assert(is_bucket(prev
->next
));
1258 node
->next
= prev
->next
;
1259 prev
->next
= flag_bucket(node
);
1264 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
1265 unsigned long min_nr_alloc_buckets
,
1266 unsigned long max_nr_buckets
,
1268 const struct cds_lfht_mm_type
*mm
,
1269 const struct rcu_flavor_struct
*flavor
,
1270 pthread_attr_t
*attr
)
1272 struct cds_lfht
*ht
;
1273 unsigned long order
;
1275 /* min_nr_alloc_buckets must be power of two */
1276 if (!min_nr_alloc_buckets
|| (min_nr_alloc_buckets
& (min_nr_alloc_buckets
- 1)))
1279 /* init_size must be power of two */
1280 if (!init_size
|| (init_size
& (init_size
- 1)))
1283 /* max_nr_buckets == 0 for order based mm means infinite */
1284 if (mm
== &cds_lfht_mm_order
&& !max_nr_buckets
)
1285 max_nr_buckets
= 1UL << (MAX_TABLE_ORDER
- 1);
1287 /* max_nr_buckets must be power of two */
1288 if (!max_nr_buckets
|| (max_nr_buckets
& (max_nr_buckets
- 1)))
1291 min_nr_alloc_buckets
= max(min_nr_alloc_buckets
, MIN_TABLE_SIZE
);
1292 init_size
= max(init_size
, MIN_TABLE_SIZE
);
1293 max_nr_buckets
= max(max_nr_buckets
, min_nr_alloc_buckets
);
1294 init_size
= min(init_size
, max_nr_buckets
);
1296 ht
= mm
->alloc_cds_lfht(min_nr_alloc_buckets
, max_nr_buckets
);
1298 assert(ht
->mm
== mm
);
1299 assert(ht
->bucket_at
== mm
->bucket_at
);
1302 ht
->flavor
= flavor
;
1303 ht
->resize_attr
= attr
;
1304 alloc_split_items_count(ht
);
1305 /* this mutex should not nest in read-side C.S. */
1306 pthread_mutex_init(&ht
->resize_mutex
, NULL
);
1307 order
= get_count_order_ulong(init_size
);
1308 ht
->resize_target
= 1UL << order
;
1309 cds_lfht_create_bucket(ht
, 1UL << order
);
1310 ht
->size
= 1UL << order
;
1314 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
1315 cds_lfht_match_fct match
, const void *key
,
1316 struct cds_lfht_iter
*iter
)
1318 struct cds_lfht_node
*node
, *next
, *bucket
;
1319 unsigned long reverse_hash
, size
;
1321 reverse_hash
= bit_reverse_ulong(hash
);
1323 size
= rcu_dereference(ht
->size
);
1324 bucket
= lookup_bucket(ht
, size
, hash
);
1325 /* We can always skip the bucket node initially */
1326 node
= rcu_dereference(bucket
->next
);
1327 node
= clear_flag(node
);
1329 if (caa_unlikely(is_end(node
))) {
1333 if (caa_unlikely(node
->reverse_hash
> reverse_hash
)) {
1337 next
= rcu_dereference(node
->next
);
1338 assert(node
== clear_flag(node
));
1339 if (caa_likely(!is_removed(next
))
1341 && node
->reverse_hash
== reverse_hash
1342 && caa_likely(match(node
, key
))) {
1345 node
= clear_flag(next
);
1347 assert(!node
|| !is_bucket(rcu_dereference(node
->next
)));
1352 void cds_lfht_next_duplicate(struct cds_lfht
*ht
, cds_lfht_match_fct match
,
1353 const void *key
, struct cds_lfht_iter
*iter
)
1355 struct cds_lfht_node
*node
, *next
;
1356 unsigned long reverse_hash
;
1359 reverse_hash
= node
->reverse_hash
;
1361 node
= clear_flag(next
);
1364 if (caa_unlikely(is_end(node
))) {
1368 if (caa_unlikely(node
->reverse_hash
> reverse_hash
)) {
1372 next
= rcu_dereference(node
->next
);
1373 if (caa_likely(!is_removed(next
))
1375 && caa_likely(match(node
, key
))) {
1378 node
= clear_flag(next
);
1380 assert(!node
|| !is_bucket(rcu_dereference(node
->next
)));
1385 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1387 struct cds_lfht_node
*node
, *next
;
1389 node
= clear_flag(iter
->next
);
1391 if (caa_unlikely(is_end(node
))) {
1395 next
= rcu_dereference(node
->next
);
1396 if (caa_likely(!is_removed(next
))
1397 && !is_bucket(next
)) {
1400 node
= clear_flag(next
);
1402 assert(!node
|| !is_bucket(rcu_dereference(node
->next
)));
1407 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1410 * Get next after first bucket node. The first bucket node is the
1411 * first node of the linked list.
1413 iter
->next
= bucket_at(ht
, 0)->next
;
1414 cds_lfht_next(ht
, iter
);
1417 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
1418 struct cds_lfht_node
*node
)
1422 node
->reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1423 size
= rcu_dereference(ht
->size
);
1424 _cds_lfht_add(ht
, NULL
, NULL
, size
, node
, NULL
, 0);
1425 ht_count_add(ht
, size
, hash
);
1428 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
1430 cds_lfht_match_fct match
,
1432 struct cds_lfht_node
*node
)
1435 struct cds_lfht_iter iter
;
1437 node
->reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1438 size
= rcu_dereference(ht
->size
);
1439 _cds_lfht_add(ht
, match
, key
, size
, node
, &iter
, 0);
1440 if (iter
.node
== node
)
1441 ht_count_add(ht
, size
, hash
);
1445 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
1447 cds_lfht_match_fct match
,
1449 struct cds_lfht_node
*node
)
1452 struct cds_lfht_iter iter
;
1454 node
->reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1455 size
= rcu_dereference(ht
->size
);
1457 _cds_lfht_add(ht
, match
, key
, size
, node
, &iter
, 0);
1458 if (iter
.node
== node
) {
1459 ht_count_add(ht
, size
, hash
);
1463 if (!_cds_lfht_replace(ht
, size
, iter
.node
, iter
.next
, node
))
1468 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
1469 struct cds_lfht_node
*new_node
)
1473 size
= rcu_dereference(ht
->size
);
1474 return _cds_lfht_replace(ht
, size
, old_iter
->node
, old_iter
->next
,
1478 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1480 unsigned long size
, hash
;
1483 size
= rcu_dereference(ht
->size
);
1484 ret
= _cds_lfht_del(ht
, size
, iter
->node
, 0);
1486 hash
= bit_reverse_ulong(iter
->node
->reverse_hash
);
1487 ht_count_del(ht
, size
, hash
);
1493 int cds_lfht_delete_bucket(struct cds_lfht
*ht
)
1495 struct cds_lfht_node
*node
;
1496 unsigned long order
, i
, size
;
1498 /* Check that the table is empty */
1499 node
= bucket_at(ht
, 0);
1501 node
= clear_flag(node
)->next
;
1502 if (!is_bucket(node
))
1504 assert(!is_removed(node
));
1505 } while (!is_end(node
));
1507 * size accessed without rcu_dereference because hash table is
1511 /* Internal sanity check: all nodes left should be bucket */
1512 for (i
= 0; i
< size
; i
++) {
1513 node
= bucket_at(ht
, i
);
1514 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1515 i
, i
, bit_reverse_ulong(node
->reverse_hash
));
1516 assert(is_bucket(node
->next
));
1519 for (order
= get_count_order_ulong(size
); (long)order
>= 0; order
--)
1520 cds_lfht_free_bucket_table(ht
, order
);
1526 * Should only be called when no more concurrent readers nor writers can
1527 * possibly access the table.
1529 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
)
1533 /* Wait for in-flight resize operations to complete */
1534 _CMM_STORE_SHARED(ht
->in_progress_destroy
, 1);
1535 cmm_smp_mb(); /* Store destroy before load resize */
1536 while (uatomic_read(&ht
->in_progress_resize
))
1537 poll(NULL
, 0, 100); /* wait for 100ms */
1538 ret
= cds_lfht_delete_bucket(ht
);
1541 free_split_items_count(ht
);
1543 *attr
= ht
->resize_attr
;
1548 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
1549 long *approx_before
,
1550 unsigned long *count
,
1551 unsigned long *removed
,
1554 struct cds_lfht_node
*node
, *next
;
1555 unsigned long nr_bucket
= 0;
1558 if (ht
->split_count
) {
1561 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1562 *approx_before
+= uatomic_read(&ht
->split_count
[i
].add
);
1563 *approx_before
-= uatomic_read(&ht
->split_count
[i
].del
);
1570 /* Count non-bucket nodes in the table */
1571 node
= bucket_at(ht
, 0);
1573 next
= rcu_dereference(node
->next
);
1574 if (is_removed(next
)) {
1575 if (!is_bucket(next
))
1579 } else if (!is_bucket(next
))
1583 node
= clear_flag(next
);
1584 } while (!is_end(node
));
1585 dbg_printf("number of bucket nodes: %lu\n", nr_bucket
);
1587 if (ht
->split_count
) {
1590 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1591 *approx_after
+= uatomic_read(&ht
->split_count
[i
].add
);
1592 *approx_after
-= uatomic_read(&ht
->split_count
[i
].del
);
1597 /* called with resize mutex held */
1599 void _do_cds_lfht_grow(struct cds_lfht
*ht
,
1600 unsigned long old_size
, unsigned long new_size
)
1602 unsigned long old_order
, new_order
;
1604 old_order
= get_count_order_ulong(old_size
);
1605 new_order
= get_count_order_ulong(new_size
);
1606 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1607 old_size
, old_order
, new_size
, new_order
);
1608 assert(new_size
> old_size
);
1609 init_table(ht
, old_order
+ 1, new_order
);
1612 /* called with resize mutex held */
1614 void _do_cds_lfht_shrink(struct cds_lfht
*ht
,
1615 unsigned long old_size
, unsigned long new_size
)
1617 unsigned long old_order
, new_order
;
1619 new_size
= max(new_size
, MIN_TABLE_SIZE
);
1620 old_order
= get_count_order_ulong(old_size
);
1621 new_order
= get_count_order_ulong(new_size
);
1622 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1623 old_size
, old_order
, new_size
, new_order
);
1624 assert(new_size
< old_size
);
1626 /* Remove and unlink all bucket nodes to remove. */
1627 fini_table(ht
, new_order
+ 1, old_order
);
1631 /* called with resize mutex held */
1633 void _do_cds_lfht_resize(struct cds_lfht
*ht
)
1635 unsigned long new_size
, old_size
;
1638 * Resize table, re-do if the target size has changed under us.
1641 assert(uatomic_read(&ht
->in_progress_resize
));
1642 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1644 ht
->resize_initiated
= 1;
1645 old_size
= ht
->size
;
1646 new_size
= CMM_LOAD_SHARED(ht
->resize_target
);
1647 if (old_size
< new_size
)
1648 _do_cds_lfht_grow(ht
, old_size
, new_size
);
1649 else if (old_size
> new_size
)
1650 _do_cds_lfht_shrink(ht
, old_size
, new_size
);
1651 ht
->resize_initiated
= 0;
1652 /* write resize_initiated before read resize_target */
1654 } while (ht
->size
!= CMM_LOAD_SHARED(ht
->resize_target
));
1658 unsigned long resize_target_grow(struct cds_lfht
*ht
, unsigned long new_size
)
1660 return _uatomic_xchg_monotonic_increase(&ht
->resize_target
, new_size
);
1664 void resize_target_update_count(struct cds_lfht
*ht
,
1665 unsigned long count
)
1667 count
= max(count
, MIN_TABLE_SIZE
);
1668 count
= min(count
, ht
->max_nr_buckets
);
1669 uatomic_set(&ht
->resize_target
, count
);
1672 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
)
1674 resize_target_update_count(ht
, new_size
);
1675 CMM_STORE_SHARED(ht
->resize_initiated
, 1);
1676 ht
->flavor
->thread_offline();
1677 pthread_mutex_lock(&ht
->resize_mutex
);
1678 _do_cds_lfht_resize(ht
);
1679 pthread_mutex_unlock(&ht
->resize_mutex
);
1680 ht
->flavor
->thread_online();
1684 void do_resize_cb(struct rcu_head
*head
)
1686 struct rcu_resize_work
*work
=
1687 caa_container_of(head
, struct rcu_resize_work
, head
);
1688 struct cds_lfht
*ht
= work
->ht
;
1690 ht
->flavor
->thread_offline();
1691 pthread_mutex_lock(&ht
->resize_mutex
);
1692 _do_cds_lfht_resize(ht
);
1693 pthread_mutex_unlock(&ht
->resize_mutex
);
1694 ht
->flavor
->thread_online();
1696 cmm_smp_mb(); /* finish resize before decrement */
1697 uatomic_dec(&ht
->in_progress_resize
);
1701 void __cds_lfht_resize_lazy_launch(struct cds_lfht
*ht
)
1703 struct rcu_resize_work
*work
;
1705 /* Store resize_target before read resize_initiated */
1707 if (!CMM_LOAD_SHARED(ht
->resize_initiated
)) {
1708 uatomic_inc(&ht
->in_progress_resize
);
1709 cmm_smp_mb(); /* increment resize count before load destroy */
1710 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
)) {
1711 uatomic_dec(&ht
->in_progress_resize
);
1714 work
= malloc(sizeof(*work
));
1716 ht
->flavor
->update_call_rcu(&work
->head
, do_resize_cb
);
1717 CMM_STORE_SHARED(ht
->resize_initiated
, 1);
1722 void cds_lfht_resize_lazy_grow(struct cds_lfht
*ht
, unsigned long size
, int growth
)
1724 unsigned long target_size
= size
<< growth
;
1726 target_size
= min(target_size
, ht
->max_nr_buckets
);
1727 if (resize_target_grow(ht
, target_size
) >= target_size
)
1730 __cds_lfht_resize_lazy_launch(ht
);
1734 * We favor grow operations over shrink. A shrink operation never occurs
1735 * if a grow operation is queued for lazy execution. A grow operation
1736 * cancels any pending shrink lazy execution.
1739 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
1740 unsigned long count
)
1742 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
1744 count
= max(count
, MIN_TABLE_SIZE
);
1745 count
= min(count
, ht
->max_nr_buckets
);
1747 return; /* Already the right size, no resize needed */
1748 if (count
> size
) { /* lazy grow */
1749 if (resize_target_grow(ht
, count
) >= count
)
1751 } else { /* lazy shrink */
1755 s
= uatomic_cmpxchg(&ht
->resize_target
, size
, count
);
1757 break; /* no resize needed */
1759 return; /* growing is/(was just) in progress */
1761 return; /* some other thread do shrink */
1765 __cds_lfht_resize_lazy_launch(ht
);