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
;
540 if (caa_unlikely(!ht
->split_count
))
542 index
= ht_get_split_count_index(hash
);
543 split_count
= uatomic_add_return(&ht
->split_count
[index
].add
, 1);
544 if (caa_unlikely(!(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))) {
547 dbg_printf("add split count %lu\n", split_count
);
548 count
= uatomic_add_return(&ht
->count
,
549 1UL << COUNT_COMMIT_ORDER
);
551 if (!(count
& (count
- 1))) {
552 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) < size
)
554 dbg_printf("add set global %ld\n", count
);
555 cds_lfht_resize_lazy_count(ht
, size
,
556 count
>> (CHAIN_LEN_TARGET
- 1));
562 void ht_count_del(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
564 unsigned long split_count
;
567 if (caa_unlikely(!ht
->split_count
))
569 index
= ht_get_split_count_index(hash
);
570 split_count
= uatomic_add_return(&ht
->split_count
[index
].del
, 1);
571 if (caa_unlikely(!(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))) {
574 dbg_printf("del split count %lu\n", split_count
);
575 count
= uatomic_add_return(&ht
->count
,
576 -(1UL << COUNT_COMMIT_ORDER
));
578 if (!(count
& (count
- 1))) {
579 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) >= size
)
581 dbg_printf("del set global %ld\n", count
);
583 * Don't shrink table if the number of nodes is below a
586 if (count
< (1UL << COUNT_COMMIT_ORDER
) * (split_count_mask
+ 1))
588 cds_lfht_resize_lazy_count(ht
, size
,
589 count
>> (CHAIN_LEN_TARGET
- 1));
595 void check_resize(struct cds_lfht
*ht
, unsigned long size
, uint32_t chain_len
)
599 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
601 count
= uatomic_read(&ht
->count
);
603 * Use bucket-local length for small table expand and for
604 * environments lacking per-cpu data support.
606 if (count
>= (1UL << COUNT_COMMIT_ORDER
))
609 dbg_printf("WARNING: large chain length: %u.\n",
611 if (chain_len
>= CHAIN_LEN_RESIZE_THRESHOLD
)
612 cds_lfht_resize_lazy_grow(ht
, size
,
613 get_count_order_u32(chain_len
- (CHAIN_LEN_TARGET
- 1)));
617 struct cds_lfht_node
*clear_flag(struct cds_lfht_node
*node
)
619 return (struct cds_lfht_node
*) (((unsigned long) node
) & ~FLAGS_MASK
);
623 int is_removed(struct cds_lfht_node
*node
)
625 return ((unsigned long) node
) & REMOVED_FLAG
;
629 struct cds_lfht_node
*flag_removed(struct cds_lfht_node
*node
)
631 return (struct cds_lfht_node
*) (((unsigned long) node
) | REMOVED_FLAG
);
635 int is_bucket(struct cds_lfht_node
*node
)
637 return ((unsigned long) node
) & BUCKET_FLAG
;
641 struct cds_lfht_node
*flag_bucket(struct cds_lfht_node
*node
)
643 return (struct cds_lfht_node
*) (((unsigned long) node
) | BUCKET_FLAG
);
647 struct cds_lfht_node
*get_end(void)
649 return (struct cds_lfht_node
*) END_VALUE
;
653 int is_end(struct cds_lfht_node
*node
)
655 return clear_flag(node
) == (struct cds_lfht_node
*) END_VALUE
;
659 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr
,
662 unsigned long old1
, old2
;
664 old1
= uatomic_read(ptr
);
669 } while ((old1
= uatomic_cmpxchg(ptr
, old2
, v
)) != old2
);
674 void cds_lfht_alloc_bucket_table(struct cds_lfht
*ht
, unsigned long order
)
676 return ht
->mm
->alloc_bucket_table(ht
, order
);
680 * cds_lfht_free_bucket_table() should be called with decreasing order.
681 * When cds_lfht_free_bucket_table(0) is called, it means the whole
685 void cds_lfht_free_bucket_table(struct cds_lfht
*ht
, unsigned long order
)
687 return ht
->mm
->free_bucket_table(ht
, order
);
691 struct cds_lfht_node
*bucket_at(struct cds_lfht
*ht
, unsigned long index
)
693 return ht
->bucket_at(ht
, index
);
697 struct cds_lfht_node
*lookup_bucket(struct cds_lfht
*ht
, unsigned long size
,
701 return bucket_at(ht
, hash
& (size
- 1));
705 * Remove all logically deleted nodes from a bucket up to a certain node key.
708 void _cds_lfht_gc_bucket(struct cds_lfht_node
*bucket
, struct cds_lfht_node
*node
)
710 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_next
;
712 assert(!is_bucket(bucket
));
713 assert(!is_removed(bucket
));
714 assert(!is_bucket(node
));
715 assert(!is_removed(node
));
718 /* We can always skip the bucket node initially */
719 iter
= rcu_dereference(iter_prev
->next
);
720 assert(!is_removed(iter
));
721 assert(iter_prev
->reverse_hash
<= node
->reverse_hash
);
723 * We should never be called with bucket (start of chain)
724 * and logically removed node (end of path compression
725 * marker) being the actual same node. This would be a
726 * bug in the algorithm implementation.
728 assert(bucket
!= node
);
730 if (caa_unlikely(is_end(iter
)))
732 if (caa_likely(clear_flag(iter
)->reverse_hash
> node
->reverse_hash
))
734 next
= rcu_dereference(clear_flag(iter
)->next
);
735 if (caa_likely(is_removed(next
)))
737 iter_prev
= clear_flag(iter
);
740 assert(!is_removed(iter
));
742 new_next
= flag_bucket(clear_flag(next
));
744 new_next
= clear_flag(next
);
745 (void) uatomic_cmpxchg(&iter_prev
->next
, iter
, new_next
);
751 int _cds_lfht_replace(struct cds_lfht
*ht
, unsigned long size
,
752 struct cds_lfht_node
*old_node
,
753 struct cds_lfht_node
*old_next
,
754 struct cds_lfht_node
*new_node
)
756 struct cds_lfht_node
*bucket
, *ret_next
;
758 if (!old_node
) /* Return -ENOENT if asked to replace NULL node */
761 assert(!is_removed(old_node
));
762 assert(!is_bucket(old_node
));
763 assert(!is_removed(new_node
));
764 assert(!is_bucket(new_node
));
765 assert(new_node
!= old_node
);
767 /* Insert after node to be replaced */
768 if (is_removed(old_next
)) {
770 * Too late, the old node has been removed under us
771 * between lookup and replace. Fail.
775 assert(!is_bucket(old_next
));
776 assert(new_node
!= clear_flag(old_next
));
777 new_node
->next
= clear_flag(old_next
);
779 * Here is the whole trick for lock-free replace: we add
780 * the replacement node _after_ the node we want to
781 * replace by atomically setting its next pointer at the
782 * same time we set its removal flag. Given that
783 * the lookups/get next use an iterator aware of the
784 * next pointer, they will either skip the old node due
785 * to the removal flag and see the new node, or use
786 * the old node, but will not see the new one.
788 ret_next
= uatomic_cmpxchg(&old_node
->next
,
789 old_next
, flag_removed(new_node
));
790 if (ret_next
== old_next
)
791 break; /* We performed the replacement. */
796 * Ensure that the old node is not visible to readers anymore:
797 * lookup for the node, and remove it (along with any other
798 * logically removed node) if found.
800 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(old_node
->reverse_hash
));
801 _cds_lfht_gc_bucket(bucket
, new_node
);
803 assert(is_removed(rcu_dereference(old_node
->next
)));
808 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
809 * mode. A NULL unique_ret allows creation of duplicate keys.
812 void _cds_lfht_add(struct cds_lfht
*ht
,
813 cds_lfht_match_fct match
,
816 struct cds_lfht_node
*node
,
817 struct cds_lfht_iter
*unique_ret
,
820 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_node
, *new_next
,
822 struct cds_lfht_node
*bucket
;
824 assert(!is_bucket(node
));
825 assert(!is_removed(node
));
826 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->reverse_hash
));
828 uint32_t chain_len
= 0;
831 * iter_prev points to the non-removed node prior to the
835 /* We can always skip the bucket node initially */
836 iter
= rcu_dereference(iter_prev
->next
);
837 assert(iter_prev
->reverse_hash
<= node
->reverse_hash
);
839 if (caa_unlikely(is_end(iter
)))
841 if (caa_likely(clear_flag(iter
)->reverse_hash
> node
->reverse_hash
))
844 /* bucket node is the first node of the identical-hash-value chain */
845 if (bucket_flag
&& clear_flag(iter
)->reverse_hash
== node
->reverse_hash
)
848 next
= rcu_dereference(clear_flag(iter
)->next
);
849 if (caa_unlikely(is_removed(next
)))
855 && clear_flag(iter
)->reverse_hash
== node
->reverse_hash
) {
856 struct cds_lfht_iter d_iter
= { .node
= node
, .next
= iter
, };
859 * uniquely adding inserts the node as the first
860 * node of the identical-hash-value node chain.
862 * This semantic ensures no duplicated keys
863 * should ever be observable in the table
864 * (including observe one node by one node
865 * by forward iterations)
867 cds_lfht_next_duplicate(ht
, match
, key
, &d_iter
);
871 *unique_ret
= d_iter
;
875 /* Only account for identical reverse hash once */
876 if (iter_prev
->reverse_hash
!= clear_flag(iter
)->reverse_hash
878 check_resize(ht
, size
, ++chain_len
);
879 iter_prev
= clear_flag(iter
);
884 assert(node
!= clear_flag(iter
));
885 assert(!is_removed(iter_prev
));
886 assert(!is_removed(iter
));
887 assert(iter_prev
!= node
);
889 node
->next
= clear_flag(iter
);
891 node
->next
= flag_bucket(clear_flag(iter
));
893 new_node
= flag_bucket(node
);
896 if (uatomic_cmpxchg(&iter_prev
->next
, iter
,
898 continue; /* retry */
905 assert(!is_removed(iter
));
907 new_next
= flag_bucket(clear_flag(next
));
909 new_next
= clear_flag(next
);
910 (void) uatomic_cmpxchg(&iter_prev
->next
, iter
, new_next
);
915 unique_ret
->node
= return_node
;
916 /* unique_ret->next left unset, never used. */
921 int _cds_lfht_del(struct cds_lfht
*ht
, unsigned long size
,
922 struct cds_lfht_node
*node
,
925 struct cds_lfht_node
*bucket
, *next
, *old
;
927 if (!node
) /* Return -ENOENT if asked to delete NULL node */
930 /* logically delete the node */
931 assert(!is_bucket(node
));
932 assert(!is_removed(node
));
933 old
= rcu_dereference(node
->next
);
935 struct cds_lfht_node
*new_next
;
938 if (caa_unlikely(is_removed(next
)))
941 assert(is_bucket(next
));
943 assert(!is_bucket(next
));
944 new_next
= flag_removed(next
);
945 old
= uatomic_cmpxchg(&node
->next
, next
, new_next
);
946 } while (old
!= next
);
947 /* We performed the (logical) deletion. */
950 * Ensure that the node is not visible to readers anymore: lookup for
951 * the node, and remove it (along with any other logically removed node)
954 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->reverse_hash
));
955 _cds_lfht_gc_bucket(bucket
, node
);
957 assert(is_removed(rcu_dereference(node
->next
)));
962 void *partition_resize_thread(void *arg
)
964 struct partition_resize_work
*work
= arg
;
966 work
->ht
->flavor
->register_thread();
967 work
->fct(work
->ht
, work
->i
, work
->start
, work
->len
);
968 work
->ht
->flavor
->unregister_thread();
973 void partition_resize_helper(struct cds_lfht
*ht
, unsigned long i
,
975 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
976 unsigned long start
, unsigned long len
))
978 unsigned long partition_len
;
979 struct partition_resize_work
*work
;
981 unsigned long nr_threads
;
984 * Note: nr_cpus_mask + 1 is always power of 2.
985 * We spawn just the number of threads we need to satisfy the minimum
986 * partition size, up to the number of CPUs in the system.
988 if (nr_cpus_mask
> 0) {
989 nr_threads
= min(nr_cpus_mask
+ 1,
990 len
>> MIN_PARTITION_PER_THREAD_ORDER
);
994 partition_len
= len
>> get_count_order_ulong(nr_threads
);
995 work
= calloc(nr_threads
, sizeof(*work
));
997 for (thread
= 0; thread
< nr_threads
; thread
++) {
998 work
[thread
].ht
= ht
;
1000 work
[thread
].len
= partition_len
;
1001 work
[thread
].start
= thread
* partition_len
;
1002 work
[thread
].fct
= fct
;
1003 ret
= pthread_create(&(work
[thread
].thread_id
), ht
->resize_attr
,
1004 partition_resize_thread
, &work
[thread
]);
1007 for (thread
= 0; thread
< nr_threads
; thread
++) {
1008 ret
= pthread_join(work
[thread
].thread_id
, NULL
);
1015 * Holding RCU read lock to protect _cds_lfht_add against memory
1016 * reclaim that could be performed by other call_rcu worker threads (ABA
1019 * When we reach a certain length, we can split this population phase over
1020 * many worker threads, based on the number of CPUs available in the system.
1021 * This should therefore take care of not having the expand lagging behind too
1022 * many concurrent insertion threads by using the scheduler's ability to
1023 * schedule bucket node population fairly with insertions.
1026 void init_table_populate_partition(struct cds_lfht
*ht
, unsigned long i
,
1027 unsigned long start
, unsigned long len
)
1029 unsigned long j
, size
= 1UL << (i
- 1);
1031 assert(i
> MIN_TABLE_ORDER
);
1032 ht
->flavor
->read_lock();
1033 for (j
= size
+ start
; j
< size
+ start
+ len
; j
++) {
1034 struct cds_lfht_node
*new_node
= bucket_at(ht
, j
);
1036 assert(j
>= size
&& j
< (size
<< 1));
1037 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1039 new_node
->reverse_hash
= bit_reverse_ulong(j
);
1040 _cds_lfht_add(ht
, NULL
, NULL
, size
, new_node
, NULL
, 1);
1042 ht
->flavor
->read_unlock();
1046 void init_table_populate(struct cds_lfht
*ht
, unsigned long i
,
1049 assert(nr_cpus_mask
!= -1);
1050 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1051 ht
->flavor
->thread_online();
1052 init_table_populate_partition(ht
, i
, 0, len
);
1053 ht
->flavor
->thread_offline();
1056 partition_resize_helper(ht
, i
, len
, init_table_populate_partition
);
1060 void init_table(struct cds_lfht
*ht
,
1061 unsigned long first_order
, unsigned long last_order
)
1065 dbg_printf("init table: first_order %lu last_order %lu\n",
1066 first_order
, last_order
);
1067 assert(first_order
> MIN_TABLE_ORDER
);
1068 for (i
= first_order
; i
<= last_order
; i
++) {
1071 len
= 1UL << (i
- 1);
1072 dbg_printf("init order %lu len: %lu\n", i
, len
);
1074 /* Stop expand if the resize target changes under us */
1075 if (CMM_LOAD_SHARED(ht
->resize_target
) < (1UL << i
))
1078 cds_lfht_alloc_bucket_table(ht
, i
);
1081 * Set all bucket nodes reverse hash values for a level and
1082 * link all bucket nodes into the table.
1084 init_table_populate(ht
, i
, len
);
1087 * Update table size.
1089 cmm_smp_wmb(); /* populate data before RCU size */
1090 CMM_STORE_SHARED(ht
->size
, 1UL << i
);
1092 dbg_printf("init new size: %lu\n", 1UL << i
);
1093 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1099 * Holding RCU read lock to protect _cds_lfht_remove against memory
1100 * reclaim that could be performed by other call_rcu worker threads (ABA
1102 * For a single level, we logically remove and garbage collect each node.
1104 * As a design choice, we perform logical removal and garbage collection on a
1105 * node-per-node basis to simplify this algorithm. We also assume keeping good
1106 * cache locality of the operation would overweight possible performance gain
1107 * that could be achieved by batching garbage collection for multiple levels.
1108 * However, this would have to be justified by benchmarks.
1110 * Concurrent removal and add operations are helping us perform garbage
1111 * collection of logically removed nodes. We guarantee that all logically
1112 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1113 * invoked to free a hole level of bucket nodes (after a grace period).
1115 * Logical removal and garbage collection can therefore be done in batch or on a
1116 * node-per-node basis, as long as the guarantee above holds.
1118 * When we reach a certain length, we can split this removal over many worker
1119 * threads, based on the number of CPUs available in the system. This should
1120 * take care of not letting resize process lag behind too many concurrent
1121 * updater threads actively inserting into the hash table.
1124 void remove_table_partition(struct cds_lfht
*ht
, unsigned long i
,
1125 unsigned long start
, unsigned long len
)
1127 unsigned long j
, size
= 1UL << (i
- 1);
1129 assert(i
> MIN_TABLE_ORDER
);
1130 ht
->flavor
->read_lock();
1131 for (j
= size
+ start
; j
< size
+ start
+ len
; j
++) {
1132 struct cds_lfht_node
*fini_node
= bucket_at(ht
, j
);
1134 assert(j
>= size
&& j
< (size
<< 1));
1135 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1137 fini_node
->reverse_hash
= bit_reverse_ulong(j
);
1138 (void) _cds_lfht_del(ht
, size
, fini_node
, 1);
1140 ht
->flavor
->read_unlock();
1144 void remove_table(struct cds_lfht
*ht
, unsigned long i
, unsigned long len
)
1147 assert(nr_cpus_mask
!= -1);
1148 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1149 ht
->flavor
->thread_online();
1150 remove_table_partition(ht
, i
, 0, len
);
1151 ht
->flavor
->thread_offline();
1154 partition_resize_helper(ht
, i
, len
, remove_table_partition
);
1158 void fini_table(struct cds_lfht
*ht
,
1159 unsigned long first_order
, unsigned long last_order
)
1162 unsigned long free_by_rcu_order
= 0;
1164 dbg_printf("fini table: first_order %lu last_order %lu\n",
1165 first_order
, last_order
);
1166 assert(first_order
> MIN_TABLE_ORDER
);
1167 for (i
= last_order
; i
>= first_order
; i
--) {
1170 len
= 1UL << (i
- 1);
1171 dbg_printf("fini order %lu len: %lu\n", i
, len
);
1173 /* Stop shrink if the resize target changes under us */
1174 if (CMM_LOAD_SHARED(ht
->resize_target
) > (1UL << (i
- 1)))
1177 cmm_smp_wmb(); /* populate data before RCU size */
1178 CMM_STORE_SHARED(ht
->size
, 1UL << (i
- 1));
1181 * We need to wait for all add operations to reach Q.S. (and
1182 * thus use the new table for lookups) before we can start
1183 * releasing the old bucket nodes. Otherwise their lookup will
1184 * return a logically removed node as insert position.
1186 ht
->flavor
->update_synchronize_rcu();
1187 if (free_by_rcu_order
)
1188 cds_lfht_free_bucket_table(ht
, free_by_rcu_order
);
1191 * Set "removed" flag in bucket nodes about to be removed.
1192 * Unlink all now-logically-removed bucket node pointers.
1193 * Concurrent add/remove operation are helping us doing
1196 remove_table(ht
, i
, len
);
1198 free_by_rcu_order
= i
;
1200 dbg_printf("fini new size: %lu\n", 1UL << i
);
1201 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1205 if (free_by_rcu_order
) {
1206 ht
->flavor
->update_synchronize_rcu();
1207 cds_lfht_free_bucket_table(ht
, free_by_rcu_order
);
1212 void cds_lfht_create_bucket(struct cds_lfht
*ht
, unsigned long size
)
1214 struct cds_lfht_node
*prev
, *node
;
1215 unsigned long order
, len
, i
;
1217 cds_lfht_alloc_bucket_table(ht
, 0);
1219 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1220 node
= bucket_at(ht
, 0);
1221 node
->next
= flag_bucket(get_end());
1222 node
->reverse_hash
= 0;
1224 for (order
= 1; order
< get_count_order_ulong(size
) + 1; order
++) {
1225 len
= 1UL << (order
- 1);
1226 cds_lfht_alloc_bucket_table(ht
, order
);
1228 for (i
= 0; i
< len
; i
++) {
1230 * Now, we are trying to init the node with the
1231 * hash=(len+i) (which is also a bucket with the
1232 * index=(len+i)) and insert it into the hash table,
1233 * so this node has to be inserted after the bucket
1234 * with the index=(len+i)&(len-1)=i. And because there
1235 * is no other non-bucket node nor bucket node with
1236 * larger index/hash inserted, so the bucket node
1237 * being inserted should be inserted directly linked
1238 * after the bucket node with index=i.
1240 prev
= bucket_at(ht
, i
);
1241 node
= bucket_at(ht
, len
+ i
);
1243 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1244 order
, len
+ i
, len
+ i
);
1245 node
->reverse_hash
= bit_reverse_ulong(len
+ i
);
1247 /* insert after prev */
1248 assert(is_bucket(prev
->next
));
1249 node
->next
= prev
->next
;
1250 prev
->next
= flag_bucket(node
);
1255 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
1256 unsigned long min_nr_alloc_buckets
,
1257 unsigned long max_nr_buckets
,
1259 const struct cds_lfht_mm_type
*mm
,
1260 const struct rcu_flavor_struct
*flavor
,
1261 pthread_attr_t
*attr
)
1263 struct cds_lfht
*ht
;
1264 unsigned long order
;
1266 /* min_nr_alloc_buckets must be power of two */
1267 if (!min_nr_alloc_buckets
|| (min_nr_alloc_buckets
& (min_nr_alloc_buckets
- 1)))
1270 /* init_size must be power of two */
1271 if (!init_size
|| (init_size
& (init_size
- 1)))
1274 /* max_nr_buckets == 0 for order based mm means infinite */
1275 if (mm
== &cds_lfht_mm_order
&& !max_nr_buckets
)
1276 max_nr_buckets
= 1UL << (MAX_TABLE_ORDER
- 1);
1278 /* max_nr_buckets must be power of two */
1279 if (!max_nr_buckets
|| (max_nr_buckets
& (max_nr_buckets
- 1)))
1282 min_nr_alloc_buckets
= max(min_nr_alloc_buckets
, MIN_TABLE_SIZE
);
1283 init_size
= max(init_size
, MIN_TABLE_SIZE
);
1284 max_nr_buckets
= max(max_nr_buckets
, min_nr_alloc_buckets
);
1285 init_size
= min(init_size
, max_nr_buckets
);
1287 ht
= mm
->alloc_cds_lfht(min_nr_alloc_buckets
, max_nr_buckets
);
1289 assert(ht
->mm
== mm
);
1290 assert(ht
->bucket_at
== mm
->bucket_at
);
1293 ht
->flavor
= flavor
;
1294 ht
->resize_attr
= attr
;
1295 alloc_split_items_count(ht
);
1296 /* this mutex should not nest in read-side C.S. */
1297 pthread_mutex_init(&ht
->resize_mutex
, NULL
);
1298 order
= get_count_order_ulong(init_size
);
1299 ht
->resize_target
= 1UL << order
;
1300 cds_lfht_create_bucket(ht
, 1UL << order
);
1301 ht
->size
= 1UL << order
;
1305 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
1306 cds_lfht_match_fct match
, const void *key
,
1307 struct cds_lfht_iter
*iter
)
1309 struct cds_lfht_node
*node
, *next
, *bucket
;
1310 unsigned long reverse_hash
, size
;
1312 reverse_hash
= bit_reverse_ulong(hash
);
1314 size
= rcu_dereference(ht
->size
);
1315 bucket
= lookup_bucket(ht
, size
, hash
);
1316 /* We can always skip the bucket node initially */
1317 node
= rcu_dereference(bucket
->next
);
1318 node
= clear_flag(node
);
1320 if (caa_unlikely(is_end(node
))) {
1324 if (caa_unlikely(node
->reverse_hash
> reverse_hash
)) {
1328 next
= rcu_dereference(node
->next
);
1329 assert(node
== clear_flag(node
));
1330 if (caa_likely(!is_removed(next
))
1332 && node
->reverse_hash
== reverse_hash
1333 && caa_likely(match(node
, key
))) {
1336 node
= clear_flag(next
);
1338 assert(!node
|| !is_bucket(rcu_dereference(node
->next
)));
1343 void cds_lfht_next_duplicate(struct cds_lfht
*ht
, cds_lfht_match_fct match
,
1344 const void *key
, struct cds_lfht_iter
*iter
)
1346 struct cds_lfht_node
*node
, *next
;
1347 unsigned long reverse_hash
;
1350 reverse_hash
= node
->reverse_hash
;
1352 node
= clear_flag(next
);
1355 if (caa_unlikely(is_end(node
))) {
1359 if (caa_unlikely(node
->reverse_hash
> reverse_hash
)) {
1363 next
= rcu_dereference(node
->next
);
1364 if (caa_likely(!is_removed(next
))
1366 && caa_likely(match(node
, key
))) {
1369 node
= clear_flag(next
);
1371 assert(!node
|| !is_bucket(rcu_dereference(node
->next
)));
1376 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1378 struct cds_lfht_node
*node
, *next
;
1380 node
= clear_flag(iter
->next
);
1382 if (caa_unlikely(is_end(node
))) {
1386 next
= rcu_dereference(node
->next
);
1387 if (caa_likely(!is_removed(next
))
1388 && !is_bucket(next
)) {
1391 node
= clear_flag(next
);
1393 assert(!node
|| !is_bucket(rcu_dereference(node
->next
)));
1398 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1401 * Get next after first bucket node. The first bucket node is the
1402 * first node of the linked list.
1404 iter
->next
= bucket_at(ht
, 0)->next
;
1405 cds_lfht_next(ht
, iter
);
1408 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
1409 struct cds_lfht_node
*node
)
1413 node
->reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1414 size
= rcu_dereference(ht
->size
);
1415 _cds_lfht_add(ht
, NULL
, NULL
, size
, node
, NULL
, 0);
1416 ht_count_add(ht
, size
, hash
);
1419 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
1421 cds_lfht_match_fct match
,
1423 struct cds_lfht_node
*node
)
1426 struct cds_lfht_iter iter
;
1428 node
->reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1429 size
= rcu_dereference(ht
->size
);
1430 _cds_lfht_add(ht
, match
, key
, size
, node
, &iter
, 0);
1431 if (iter
.node
== node
)
1432 ht_count_add(ht
, size
, hash
);
1436 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
1438 cds_lfht_match_fct match
,
1440 struct cds_lfht_node
*node
)
1443 struct cds_lfht_iter iter
;
1445 node
->reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1446 size
= rcu_dereference(ht
->size
);
1448 _cds_lfht_add(ht
, match
, key
, size
, node
, &iter
, 0);
1449 if (iter
.node
== node
) {
1450 ht_count_add(ht
, size
, hash
);
1454 if (!_cds_lfht_replace(ht
, size
, iter
.node
, iter
.next
, node
))
1459 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
1460 struct cds_lfht_node
*new_node
)
1464 size
= rcu_dereference(ht
->size
);
1465 return _cds_lfht_replace(ht
, size
, old_iter
->node
, old_iter
->next
,
1469 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1471 unsigned long size
, hash
;
1474 size
= rcu_dereference(ht
->size
);
1475 ret
= _cds_lfht_del(ht
, size
, iter
->node
, 0);
1477 hash
= bit_reverse_ulong(iter
->node
->reverse_hash
);
1478 ht_count_del(ht
, size
, hash
);
1484 int cds_lfht_delete_bucket(struct cds_lfht
*ht
)
1486 struct cds_lfht_node
*node
;
1487 unsigned long order
, i
, size
;
1489 /* Check that the table is empty */
1490 node
= bucket_at(ht
, 0);
1492 node
= clear_flag(node
)->next
;
1493 if (!is_bucket(node
))
1495 assert(!is_removed(node
));
1496 } while (!is_end(node
));
1498 * size accessed without rcu_dereference because hash table is
1502 /* Internal sanity check: all nodes left should be bucket */
1503 for (i
= 0; i
< size
; i
++) {
1504 node
= bucket_at(ht
, i
);
1505 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1506 i
, i
, bit_reverse_ulong(node
->reverse_hash
));
1507 assert(is_bucket(node
->next
));
1510 for (order
= get_count_order_ulong(size
); (long)order
>= 0; order
--)
1511 cds_lfht_free_bucket_table(ht
, order
);
1517 * Should only be called when no more concurrent readers nor writers can
1518 * possibly access the table.
1520 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
)
1524 /* Wait for in-flight resize operations to complete */
1525 _CMM_STORE_SHARED(ht
->in_progress_destroy
, 1);
1526 cmm_smp_mb(); /* Store destroy before load resize */
1527 while (uatomic_read(&ht
->in_progress_resize
))
1528 poll(NULL
, 0, 100); /* wait for 100ms */
1529 ret
= cds_lfht_delete_bucket(ht
);
1532 free_split_items_count(ht
);
1534 *attr
= ht
->resize_attr
;
1539 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
1540 long *approx_before
,
1541 unsigned long *count
,
1542 unsigned long *removed
,
1545 struct cds_lfht_node
*node
, *next
;
1546 unsigned long nr_bucket
= 0;
1549 if (ht
->split_count
) {
1552 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1553 *approx_before
+= uatomic_read(&ht
->split_count
[i
].add
);
1554 *approx_before
-= uatomic_read(&ht
->split_count
[i
].del
);
1561 /* Count non-bucket nodes in the table */
1562 node
= bucket_at(ht
, 0);
1564 next
= rcu_dereference(node
->next
);
1565 if (is_removed(next
)) {
1566 if (!is_bucket(next
))
1570 } else if (!is_bucket(next
))
1574 node
= clear_flag(next
);
1575 } while (!is_end(node
));
1576 dbg_printf("number of bucket nodes: %lu\n", nr_bucket
);
1578 if (ht
->split_count
) {
1581 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1582 *approx_after
+= uatomic_read(&ht
->split_count
[i
].add
);
1583 *approx_after
-= uatomic_read(&ht
->split_count
[i
].del
);
1588 /* called with resize mutex held */
1590 void _do_cds_lfht_grow(struct cds_lfht
*ht
,
1591 unsigned long old_size
, unsigned long new_size
)
1593 unsigned long old_order
, new_order
;
1595 old_order
= get_count_order_ulong(old_size
);
1596 new_order
= get_count_order_ulong(new_size
);
1597 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1598 old_size
, old_order
, new_size
, new_order
);
1599 assert(new_size
> old_size
);
1600 init_table(ht
, old_order
+ 1, new_order
);
1603 /* called with resize mutex held */
1605 void _do_cds_lfht_shrink(struct cds_lfht
*ht
,
1606 unsigned long old_size
, unsigned long new_size
)
1608 unsigned long old_order
, new_order
;
1610 new_size
= max(new_size
, MIN_TABLE_SIZE
);
1611 old_order
= get_count_order_ulong(old_size
);
1612 new_order
= get_count_order_ulong(new_size
);
1613 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1614 old_size
, old_order
, new_size
, new_order
);
1615 assert(new_size
< old_size
);
1617 /* Remove and unlink all bucket nodes to remove. */
1618 fini_table(ht
, new_order
+ 1, old_order
);
1622 /* called with resize mutex held */
1624 void _do_cds_lfht_resize(struct cds_lfht
*ht
)
1626 unsigned long new_size
, old_size
;
1629 * Resize table, re-do if the target size has changed under us.
1632 assert(uatomic_read(&ht
->in_progress_resize
));
1633 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1635 ht
->resize_initiated
= 1;
1636 old_size
= ht
->size
;
1637 new_size
= CMM_LOAD_SHARED(ht
->resize_target
);
1638 if (old_size
< new_size
)
1639 _do_cds_lfht_grow(ht
, old_size
, new_size
);
1640 else if (old_size
> new_size
)
1641 _do_cds_lfht_shrink(ht
, old_size
, new_size
);
1642 ht
->resize_initiated
= 0;
1643 /* write resize_initiated before read resize_target */
1645 } while (ht
->size
!= CMM_LOAD_SHARED(ht
->resize_target
));
1649 unsigned long resize_target_grow(struct cds_lfht
*ht
, unsigned long new_size
)
1651 return _uatomic_xchg_monotonic_increase(&ht
->resize_target
, new_size
);
1655 void resize_target_update_count(struct cds_lfht
*ht
,
1656 unsigned long count
)
1658 count
= max(count
, MIN_TABLE_SIZE
);
1659 count
= min(count
, ht
->max_nr_buckets
);
1660 uatomic_set(&ht
->resize_target
, count
);
1663 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
)
1665 resize_target_update_count(ht
, new_size
);
1666 CMM_STORE_SHARED(ht
->resize_initiated
, 1);
1667 ht
->flavor
->thread_offline();
1668 pthread_mutex_lock(&ht
->resize_mutex
);
1669 _do_cds_lfht_resize(ht
);
1670 pthread_mutex_unlock(&ht
->resize_mutex
);
1671 ht
->flavor
->thread_online();
1675 void do_resize_cb(struct rcu_head
*head
)
1677 struct rcu_resize_work
*work
=
1678 caa_container_of(head
, struct rcu_resize_work
, head
);
1679 struct cds_lfht
*ht
= work
->ht
;
1681 ht
->flavor
->thread_offline();
1682 pthread_mutex_lock(&ht
->resize_mutex
);
1683 _do_cds_lfht_resize(ht
);
1684 pthread_mutex_unlock(&ht
->resize_mutex
);
1685 ht
->flavor
->thread_online();
1687 cmm_smp_mb(); /* finish resize before decrement */
1688 uatomic_dec(&ht
->in_progress_resize
);
1692 void __cds_lfht_resize_lazy_launch(struct cds_lfht
*ht
)
1694 struct rcu_resize_work
*work
;
1696 /* Store resize_target before read resize_initiated */
1698 if (!CMM_LOAD_SHARED(ht
->resize_initiated
)) {
1699 uatomic_inc(&ht
->in_progress_resize
);
1700 cmm_smp_mb(); /* increment resize count before load destroy */
1701 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
)) {
1702 uatomic_dec(&ht
->in_progress_resize
);
1705 work
= malloc(sizeof(*work
));
1707 ht
->flavor
->update_call_rcu(&work
->head
, do_resize_cb
);
1708 CMM_STORE_SHARED(ht
->resize_initiated
, 1);
1713 void cds_lfht_resize_lazy_grow(struct cds_lfht
*ht
, unsigned long size
, int growth
)
1715 unsigned long target_size
= size
<< growth
;
1717 target_size
= min(target_size
, ht
->max_nr_buckets
);
1718 if (resize_target_grow(ht
, target_size
) >= target_size
)
1721 __cds_lfht_resize_lazy_launch(ht
);
1725 * We favor grow operations over shrink. A shrink operation never occurs
1726 * if a grow operation is queued for lazy execution. A grow operation
1727 * cancels any pending shrink lazy execution.
1730 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
1731 unsigned long count
)
1733 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
1735 count
= max(count
, MIN_TABLE_SIZE
);
1736 count
= min(count
, ht
->max_nr_buckets
);
1738 return; /* Already the right size, no resize needed */
1739 if (count
> size
) { /* lazy grow */
1740 if (resize_target_grow(ht
, count
) >= count
)
1742 } else { /* lazy shrink */
1746 s
= uatomic_cmpxchg(&ht
->resize_target
, size
, count
);
1748 break; /* no resize needed */
1750 return; /* growing is/(was just) in progress */
1752 return; /* some other thread do shrink */
1756 __cds_lfht_resize_lazy_launch(ht
);