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, as well as traversals, and use the returned objects
38 * safely by allowing memory reclaim to take place only after a grace
40 * - Add and remove operations are lock-free, and do not need to
41 * allocate memory. They need to be executed within RCU read-side
42 * critical section to ensure the objects they read are valid and to
43 * deal with the cmpxchg ABA problem.
44 * - add and add_unique operations are supported. add_unique checks if
45 * the node key already exists in the hash table. It ensures not to
46 * populate a duplicate key if the node key already exists in the hash
48 * - The resize operation executes concurrently with
49 * add/add_unique/add_replace/remove/lookup/traversal.
50 * - Hash table nodes are contained within a split-ordered list. This
51 * list is ordered by incrementing reversed-bits-hash value.
52 * - An index of bucket nodes is kept. These bucket nodes are the hash
53 * table "buckets". These buckets are internal nodes that allow to
54 * perform a fast hash lookup, similarly to a skip list. These
55 * buckets are chained together in the split-ordered list, which
56 * allows recursive expansion by inserting new buckets between the
57 * existing buckets. The split-ordered list allows adding new buckets
58 * between existing buckets as the table needs to grow.
59 * - The resize operation for small tables only allows expanding the
60 * hash table. It is triggered automatically by detecting long chains
61 * in the add operation.
62 * - The resize operation for larger tables (and available through an
63 * API) allows both expanding and shrinking the hash table.
64 * - Split-counters are used to keep track of the number of
65 * nodes within the hash table for automatic resize triggering.
66 * - Resize operation initiated by long chain detection is executed by a
67 * call_rcu thread, which keeps lock-freedom of add and remove.
68 * - Resize operations are protected by a mutex.
69 * - The removal operation is split in two parts: first, a "removed"
70 * flag is set in the next pointer within the node to remove. Then,
71 * a "garbage collection" is performed in the bucket containing the
72 * removed node (from the start of the bucket up to the removed node).
73 * All encountered nodes with "removed" flag set in their next
74 * pointers are removed from the linked-list. If the cmpxchg used for
75 * removal fails (due to concurrent garbage-collection or concurrent
76 * add), we retry from the beginning of the bucket. This ensures that
77 * the node with "removed" flag set is removed from the hash table
78 * (not visible to lookups anymore) before the RCU read-side critical
79 * section held across removal ends. Furthermore, this ensures that
80 * the node with "removed" flag set is removed from the linked-list
81 * before its memory is reclaimed. After setting the "removal" flag,
82 * only the thread which removal is the first to set the "removal
83 * owner" flag (with an xchg) into a node's next pointer is considered
84 * to have succeeded its removal (and thus owns the node to reclaim).
85 * Because we garbage-collect starting from an invariant node (the
86 * start-of-bucket bucket node) up to the "removed" node (or find a
87 * reverse-hash that is higher), we are sure that a successful
88 * traversal of the chain leads to a chain that is present in the
89 * linked-list (the start node is never removed) and that it does not
90 * contain the "removed" node anymore, even if concurrent delete/add
91 * operations are changing the structure of the list concurrently.
92 * - The add operations perform garbage collection of buckets if they
93 * encounter nodes with removed flag set in the bucket where they want
94 * to add their new node. This ensures lock-freedom of add operation by
95 * helping the remover unlink nodes from the list rather than to wait
97 * - There are three memory backends for the hash table buckets: the
98 * "order table", the "chunks", and the "mmap".
99 * - These bucket containers contain a compact version of the hash table
101 * - The RCU "order table":
102 * - has a first level table indexed by log2(hash index) which is
103 * copied and expanded by the resize operation. This order table
104 * allows finding the "bucket node" tables.
105 * - There is one bucket node table per hash index order. The size of
106 * each bucket node table is half the number of hashes contained in
107 * this order (except for order 0).
108 * - The RCU "chunks" is best suited for close interaction with a page
109 * allocator. It uses a linear array as index to "chunks" containing
110 * each the same number of buckets.
111 * - The RCU "mmap" memory backend uses a single memory map to hold
113 * - synchronize_rcu is used to garbage-collect the old bucket node table.
115 * Ordering Guarantees:
117 * To discuss these guarantees, we first define "read" operation as any
118 * of the the basic cds_lfht_lookup, cds_lfht_next_duplicate,
119 * cds_lfht_first, cds_lfht_next operation, as well as
120 * cds_lfht_add_unique (failure).
122 * We define "read traversal" operation as any of the following
123 * group of operations
124 * - cds_lfht_lookup followed by iteration with cds_lfht_next_duplicate
125 * (and/or cds_lfht_next, although less common).
126 * - cds_lfht_add_unique (failure) followed by iteration with
127 * cds_lfht_next_duplicate (and/or cds_lfht_next, although less
129 * - cds_lfht_first followed iteration with cds_lfht_next (and/or
130 * cds_lfht_next_duplicate, although less common).
132 * We define "write" operations as any of cds_lfht_add,
133 * cds_lfht_add_unique (success), cds_lfht_add_replace, cds_lfht_del.
135 * When cds_lfht_add_unique succeeds (returns the node passed as
136 * parameter), it acts as a "write" operation. When cds_lfht_add_unique
137 * fails (returns a node different from the one passed as parameter), it
138 * acts as a "read" operation. A cds_lfht_add_unique failure is a
139 * cds_lfht_lookup "read" operation, therefore, any ordering guarantee
140 * referring to "lookup" imply any of "lookup" or cds_lfht_add_unique
143 * We define "prior" and "later" node as nodes observable by reads and
144 * read traversals respectively before and after a write or sequence of
147 * Hash-table operations are often cascaded, for example, the pointer
148 * returned by a cds_lfht_lookup() might be passed to a cds_lfht_next(),
149 * whose return value might in turn be passed to another hash-table
150 * operation. This entire cascaded series of operations must be enclosed
151 * by a pair of matching rcu_read_lock() and rcu_read_unlock()
154 * The following ordering guarantees are offered by this hash table:
156 * A.1) "read" after "write": if there is ordering between a write and a
157 * later read, then the read is guaranteed to see the write or some
159 * A.2) "read traversal" after "write": given that there is dependency
160 * ordering between reads in a "read traversal", if there is
161 * ordering between a write and the first read of the traversal,
162 * then the "read traversal" is guaranteed to see the write or
164 * B.1) "write" after "read": if there is ordering between a read and a
165 * later write, then the read will never see the write.
166 * B.2) "write" after "read traversal": given that there is dependency
167 * ordering between reads in a "read traversal", if there is
168 * ordering between the last read of the traversal and a later
169 * write, then the "read traversal" will never see the write.
170 * C) "write" while "read traversal": if a write occurs during a "read
171 * traversal", the traversal may, or may not, see the write.
172 * D.1) "write" after "write": if there is ordering between a write and
173 * a later write, then the later write is guaranteed to see the
174 * effects of the first write.
175 * D.2) Concurrent "write" pairs: The system will assign an arbitrary
176 * order to any pair of concurrent conflicting writes.
177 * Non-conflicting writes (for example, to different keys) are
179 * E) If a grace period separates a "del" or "replace" operation
180 * and a subsequent operation, then that subsequent operation is
181 * guaranteed not to see the removed item.
182 * F) Uniqueness guarantee: given a hash table that does not contain
183 * duplicate items for a given key, there will only be one item in
184 * the hash table after an arbitrary sequence of add_unique and/or
185 * add_replace operations. Note, however, that a pair of
186 * concurrent read operations might well access two different items
188 * G.1) If a pair of lookups for a given key are ordered (e.g. by a
189 * memory barrier), then the second lookup will return the same
190 * node as the previous lookup, or some later node.
191 * G.2) A "read traversal" that starts after the end of a prior "read
192 * traversal" (ordered by memory barriers) is guaranteed to see the
193 * same nodes as the previous traversal, or some later nodes.
194 * G.3) Concurrent "read" pairs: concurrent reads are unordered. For
195 * example, if a pair of reads to the same key run concurrently
196 * with an insertion of that same key, the reads remain unordered
197 * regardless of their return values. In other words, you cannot
198 * rely on the values returned by the reads to deduce ordering.
200 * Progress guarantees:
202 * * Reads are wait-free. These operations always move forward in the
203 * hash table linked list, and this list has no loop.
204 * * Writes are lock-free. Any retry loop performed by a write operation
205 * is triggered by progress made within another update operation.
207 * Bucket node tables:
209 * hash table hash table the last all bucket node tables
210 * order size bucket node 0 1 2 3 4 5 6(index)
217 * 5 32 16 1 1 2 4 8 16
218 * 6 64 32 1 1 2 4 8 16 32
220 * When growing/shrinking, we only focus on the last bucket node table
221 * which size is (!order ? 1 : (1 << (order -1))).
223 * Example for growing/shrinking:
224 * grow hash table from order 5 to 6: init the index=6 bucket node table
225 * shrink hash table from order 6 to 5: fini the index=6 bucket node table
227 * A bit of ascii art explanation:
229 * The order index is the off-by-one compared to the actual power of 2
230 * because we use index 0 to deal with the 0 special-case.
232 * This shows the nodes for a small table ordered by reversed bits:
244 * This shows the nodes in order of non-reversed bits, linked by
245 * reversed-bit order.
250 * 2 | | 2 010 010 <- |
251 * | | | 3 011 110 | <- |
252 * 3 -> | | | 4 100 001 | |
270 #include <urcu-call-rcu.h>
271 #include <urcu/arch.h>
272 #include <urcu/uatomic.h>
273 #include <urcu/compiler.h>
277 #include "rculfhash.h"
278 #include "rculfhash-internal.h"
279 #include "urcu-flavor.h"
281 #include <common/common.h>
284 * Split-counters lazily update the global counter each 1024
285 * addition/removal. It automatically keeps track of resize required.
286 * We use the bucket length as indicator for need to expand for small
287 * tables and machines lacking per-cpu data suppport.
289 #define COUNT_COMMIT_ORDER 10
290 #define DEFAULT_SPLIT_COUNT_MASK 0xFUL
291 #define CHAIN_LEN_TARGET 1
292 #define CHAIN_LEN_RESIZE_THRESHOLD 3
295 * Define the minimum table size.
297 #define MIN_TABLE_ORDER 0
298 #define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
301 * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
303 #define MIN_PARTITION_PER_THREAD_ORDER 12
304 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
307 * The removed flag needs to be updated atomically with the pointer.
308 * It indicates that no node must attach to the node scheduled for
309 * removal, and that node garbage collection must be performed.
310 * The bucket flag does not require to be updated atomically with the
311 * pointer, but it is added as a pointer low bit flag to save space.
312 * The "removal owner" flag is used to detect which of the "del"
313 * operation that has set the "removed flag" gets to return the removed
314 * node to its caller. Note that the replace operation does not need to
315 * iteract with the "removal owner" flag, because it validates that
316 * the "removed" flag is not set before performing its cmpxchg.
318 #define REMOVED_FLAG (1UL << 0)
319 #define BUCKET_FLAG (1UL << 1)
320 #define REMOVAL_OWNER_FLAG (1UL << 2)
321 #define FLAGS_MASK ((1UL << 3) - 1)
323 /* Value of the end pointer. Should not interact with flags. */
324 #define END_VALUE NULL
327 * ht_items_count: Split-counters counting the number of node addition
328 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
329 * is set at hash table creation.
331 * These are free-running counters, never reset to zero. They count the
332 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
333 * operations to update the global counter. We choose a power-of-2 value
334 * for the trigger to deal with 32 or 64-bit overflow of the counter.
336 struct ht_items_count
{
337 unsigned long add
, del
;
338 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
341 * rcu_resize_work: Contains arguments passed to RCU worker thread
342 * responsible for performing lazy resize.
344 struct rcu_resize_work
{
345 struct rcu_head head
;
350 * partition_resize_work: Contains arguments passed to worker threads
351 * executing the hash table resize on partitions of the hash table
352 * assigned to each processor's worker thread.
354 struct partition_resize_work
{
357 unsigned long i
, start
, len
;
358 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
359 unsigned long start
, unsigned long len
);
363 * Algorithm to reverse bits in a word by lookup table, extended to
366 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
367 * Originally from Public Domain.
370 static const uint8_t BitReverseTable256
[256] =
372 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
373 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
374 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
375 R6(0), R6(2), R6(1), R6(3)
382 uint8_t bit_reverse_u8(uint8_t v
)
384 return BitReverseTable256
[v
];
387 static __attribute__((unused
))
388 uint32_t bit_reverse_u32(uint32_t v
)
390 return ((uint32_t) bit_reverse_u8(v
) << 24) |
391 ((uint32_t) bit_reverse_u8(v
>> 8) << 16) |
392 ((uint32_t) bit_reverse_u8(v
>> 16) << 8) |
393 ((uint32_t) bit_reverse_u8(v
>> 24));
396 static __attribute__((unused
))
397 uint64_t bit_reverse_u64(uint64_t v
)
399 return ((uint64_t) bit_reverse_u8(v
) << 56) |
400 ((uint64_t) bit_reverse_u8(v
>> 8) << 48) |
401 ((uint64_t) bit_reverse_u8(v
>> 16) << 40) |
402 ((uint64_t) bit_reverse_u8(v
>> 24) << 32) |
403 ((uint64_t) bit_reverse_u8(v
>> 32) << 24) |
404 ((uint64_t) bit_reverse_u8(v
>> 40) << 16) |
405 ((uint64_t) bit_reverse_u8(v
>> 48) << 8) |
406 ((uint64_t) bit_reverse_u8(v
>> 56));
410 unsigned long bit_reverse_ulong(unsigned long v
)
412 #if (CAA_BITS_PER_LONG == 32)
413 return bit_reverse_u32(v
);
415 return bit_reverse_u64(v
);
420 * fls: returns the position of the most significant bit.
421 * Returns 0 if no bit is set, else returns the position of the most
422 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
424 #if defined(__i386) || defined(__x86_64)
426 unsigned int fls_u32(uint32_t x
)
434 : "=r" (r
) : "rm" (x
));
440 #if defined(__x86_64)
442 unsigned int fls_u64(uint64_t x
)
450 : "=r" (r
) : "rm" (x
));
457 static __attribute__((unused
))
458 unsigned int fls_u64(uint64_t x
)
465 if (!(x
& 0xFFFFFFFF00000000ULL
)) {
469 if (!(x
& 0xFFFF000000000000ULL
)) {
473 if (!(x
& 0xFF00000000000000ULL
)) {
477 if (!(x
& 0xF000000000000000ULL
)) {
481 if (!(x
& 0xC000000000000000ULL
)) {
485 if (!(x
& 0x8000000000000000ULL
)) {
494 static __attribute__((unused
))
495 unsigned int fls_u32(uint32_t x
)
501 if (!(x
& 0xFFFF0000U
)) {
505 if (!(x
& 0xFF000000U
)) {
509 if (!(x
& 0xF0000000U
)) {
513 if (!(x
& 0xC0000000U
)) {
517 if (!(x
& 0x80000000U
)) {
525 unsigned int cds_lfht_fls_ulong(unsigned long x
)
527 #if (CAA_BITS_PER_LONG == 32)
535 * Return the minimum order for which x <= (1UL << order).
536 * Return -1 if x is 0.
538 int cds_lfht_get_count_order_u32(uint32_t x
)
543 return fls_u32(x
- 1);
547 * Return the minimum order for which x <= (1UL << order).
548 * Return -1 if x is 0.
550 int cds_lfht_get_count_order_ulong(unsigned long x
)
555 return cds_lfht_fls_ulong(x
- 1);
559 void cds_lfht_resize_lazy_grow(struct cds_lfht
*ht
, unsigned long size
, int growth
);
562 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
563 unsigned long count
);
565 static long nr_cpus_mask
= -1;
566 static long split_count_mask
= -1;
567 static int split_count_order
= -1;
569 #if defined(HAVE_SYSCONF)
570 static void ht_init_nr_cpus_mask(void)
574 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
580 * round up number of CPUs to next power of two, so we
581 * can use & for modulo.
583 maxcpus
= 1UL << cds_lfht_get_count_order_ulong(maxcpus
);
584 nr_cpus_mask
= maxcpus
- 1;
586 #else /* #if defined(HAVE_SYSCONF) */
587 static void ht_init_nr_cpus_mask(void)
591 #endif /* #else #if defined(HAVE_SYSCONF) */
594 void alloc_split_items_count(struct cds_lfht
*ht
)
596 struct ht_items_count
*count
;
598 if (nr_cpus_mask
== -1) {
599 ht_init_nr_cpus_mask();
600 if (nr_cpus_mask
< 0)
601 split_count_mask
= DEFAULT_SPLIT_COUNT_MASK
;
603 split_count_mask
= nr_cpus_mask
;
605 cds_lfht_get_count_order_ulong(split_count_mask
+ 1);
608 assert(split_count_mask
>= 0);
610 if (ht
->flags
& CDS_LFHT_ACCOUNTING
) {
611 ht
->split_count
= calloc(split_count_mask
+ 1, sizeof(*count
));
612 assert(ht
->split_count
);
614 ht
->split_count
= NULL
;
619 void free_split_items_count(struct cds_lfht
*ht
)
621 poison_free(ht
->split_count
);
624 #if defined(HAVE_SCHED_GETCPU) && !defined(VALGRIND)
626 int ht_get_split_count_index(unsigned long hash
)
630 assert(split_count_mask
>= 0);
631 cpu
= sched_getcpu();
632 if (caa_unlikely(cpu
< 0))
633 return hash
& split_count_mask
;
635 return cpu
& split_count_mask
;
637 #else /* #if defined(HAVE_SCHED_GETCPU) */
639 int ht_get_split_count_index(unsigned long hash
)
641 return hash
& split_count_mask
;
643 #endif /* #else #if defined(HAVE_SCHED_GETCPU) */
646 void ht_count_add(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
648 unsigned long split_count
;
652 if (caa_unlikely(!ht
->split_count
))
654 index
= ht_get_split_count_index(hash
);
655 split_count
= uatomic_add_return(&ht
->split_count
[index
].add
, 1);
656 if (caa_likely(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))
658 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
660 dbg_printf("add split count %lu\n", split_count
);
661 count
= uatomic_add_return(&ht
->count
,
662 1UL << COUNT_COMMIT_ORDER
);
663 if (caa_likely(count
& (count
- 1)))
665 /* Only if global count is power of 2 */
667 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) < size
)
669 dbg_printf("add set global %ld\n", count
);
670 cds_lfht_resize_lazy_count(ht
, size
,
671 count
>> (CHAIN_LEN_TARGET
- 1));
675 void ht_count_del(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
677 unsigned long split_count
;
681 if (caa_unlikely(!ht
->split_count
))
683 index
= ht_get_split_count_index(hash
);
684 split_count
= uatomic_add_return(&ht
->split_count
[index
].del
, 1);
685 if (caa_likely(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))
687 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
689 dbg_printf("del split count %lu\n", split_count
);
690 count
= uatomic_add_return(&ht
->count
,
691 -(1UL << COUNT_COMMIT_ORDER
));
692 if (caa_likely(count
& (count
- 1)))
694 /* Only if global count is power of 2 */
696 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) >= size
)
698 dbg_printf("del set global %ld\n", count
);
700 * Don't shrink table if the number of nodes is below a
703 if (count
< (1UL << COUNT_COMMIT_ORDER
) * (split_count_mask
+ 1))
705 cds_lfht_resize_lazy_count(ht
, size
,
706 count
>> (CHAIN_LEN_TARGET
- 1));
710 void check_resize(struct cds_lfht
*ht
, unsigned long size
, uint32_t chain_len
)
714 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
716 count
= uatomic_read(&ht
->count
);
718 * Use bucket-local length for small table expand and for
719 * environments lacking per-cpu data support.
721 if (count
>= (1UL << (COUNT_COMMIT_ORDER
+ split_count_order
)))
724 dbg_printf("WARNING: large chain length: %u.\n",
726 if (chain_len
>= CHAIN_LEN_RESIZE_THRESHOLD
) {
730 * Ideal growth calculated based on chain length.
732 growth
= cds_lfht_get_count_order_u32(chain_len
733 - (CHAIN_LEN_TARGET
- 1));
734 if ((ht
->flags
& CDS_LFHT_ACCOUNTING
)
736 >= (1UL << (COUNT_COMMIT_ORDER
737 + split_count_order
))) {
739 * If ideal growth expands the hash table size
740 * beyond the "small hash table" sizes, use the
741 * maximum small hash table size to attempt
742 * expanding the hash table. This only applies
743 * when node accounting is available, otherwise
744 * the chain length is used to expand the hash
745 * table in every case.
747 growth
= COUNT_COMMIT_ORDER
+ split_count_order
748 - cds_lfht_get_count_order_ulong(size
);
752 cds_lfht_resize_lazy_grow(ht
, size
, growth
);
757 struct cds_lfht_node
*clear_flag(struct cds_lfht_node
*node
)
759 return (struct cds_lfht_node
*) (((unsigned long) node
) & ~FLAGS_MASK
);
763 int is_removed(struct cds_lfht_node
*node
)
765 return ((unsigned long) node
) & REMOVED_FLAG
;
769 int is_bucket(struct cds_lfht_node
*node
)
771 return ((unsigned long) node
) & BUCKET_FLAG
;
775 struct cds_lfht_node
*flag_bucket(struct cds_lfht_node
*node
)
777 return (struct cds_lfht_node
*) (((unsigned long) node
) | BUCKET_FLAG
);
781 int is_removal_owner(struct cds_lfht_node
*node
)
783 return ((unsigned long) node
) & REMOVAL_OWNER_FLAG
;
787 struct cds_lfht_node
*flag_removal_owner(struct cds_lfht_node
*node
)
789 return (struct cds_lfht_node
*) (((unsigned long) node
) | REMOVAL_OWNER_FLAG
);
793 struct cds_lfht_node
*flag_removed_or_removal_owner(struct cds_lfht_node
*node
)
795 return (struct cds_lfht_node
*) (((unsigned long) node
) | REMOVED_FLAG
| REMOVAL_OWNER_FLAG
);
799 struct cds_lfht_node
*get_end(void)
801 return (struct cds_lfht_node
*) END_VALUE
;
805 int is_end(struct cds_lfht_node
*node
)
807 return clear_flag(node
) == (struct cds_lfht_node
*) END_VALUE
;
811 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr
,
814 unsigned long old1
, old2
;
816 old1
= uatomic_read(ptr
);
821 } while ((old1
= uatomic_cmpxchg(ptr
, old2
, v
)) != old2
);
826 void cds_lfht_alloc_bucket_table(struct cds_lfht
*ht
, unsigned long order
)
828 return ht
->mm
->alloc_bucket_table(ht
, order
);
832 * cds_lfht_free_bucket_table() should be called with decreasing order.
833 * When cds_lfht_free_bucket_table(0) is called, it means the whole
837 void cds_lfht_free_bucket_table(struct cds_lfht
*ht
, unsigned long order
)
839 return ht
->mm
->free_bucket_table(ht
, order
);
843 struct cds_lfht_node
*bucket_at(struct cds_lfht
*ht
, unsigned long index
)
845 return ht
->bucket_at(ht
, index
);
849 struct cds_lfht_node
*lookup_bucket(struct cds_lfht
*ht
, unsigned long size
,
853 return bucket_at(ht
, hash
& (size
- 1));
857 * Remove all logically deleted nodes from a bucket up to a certain node key.
860 void _cds_lfht_gc_bucket(struct cds_lfht_node
*bucket
, struct cds_lfht_node
*node
)
862 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_next
;
864 assert(!is_bucket(bucket
));
865 assert(!is_removed(bucket
));
866 assert(!is_bucket(node
));
867 assert(!is_removed(node
));
870 /* We can always skip the bucket node initially */
871 iter
= rcu_dereference(iter_prev
->next
);
872 assert(!is_removed(iter
));
873 assert(iter_prev
->reverse_hash
<= node
->reverse_hash
);
875 * We should never be called with bucket (start of chain)
876 * and logically removed node (end of path compression
877 * marker) being the actual same node. This would be a
878 * bug in the algorithm implementation.
880 assert(bucket
!= node
);
882 if (caa_unlikely(is_end(iter
)))
884 if (caa_likely(clear_flag(iter
)->reverse_hash
> node
->reverse_hash
))
886 next
= rcu_dereference(clear_flag(iter
)->next
);
887 if (caa_likely(is_removed(next
)))
889 iter_prev
= clear_flag(iter
);
892 assert(!is_removed(iter
));
894 new_next
= flag_bucket(clear_flag(next
));
896 new_next
= clear_flag(next
);
897 (void) uatomic_cmpxchg(&iter_prev
->next
, iter
, new_next
);
902 int _cds_lfht_replace(struct cds_lfht
*ht
, unsigned long size
,
903 struct cds_lfht_node
*old_node
,
904 struct cds_lfht_node
*old_next
,
905 struct cds_lfht_node
*new_node
)
907 struct cds_lfht_node
*bucket
, *ret_next
;
909 if (!old_node
) /* Return -ENOENT if asked to replace NULL node */
912 assert(!is_removed(old_node
));
913 assert(!is_bucket(old_node
));
914 assert(!is_removed(new_node
));
915 assert(!is_bucket(new_node
));
916 assert(new_node
!= old_node
);
918 /* Insert after node to be replaced */
919 if (is_removed(old_next
)) {
921 * Too late, the old node has been removed under us
922 * between lookup and replace. Fail.
926 assert(old_next
== clear_flag(old_next
));
927 assert(new_node
!= old_next
);
929 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
930 * flag. It is either set atomically at the same time
931 * (replace) or after (del).
933 assert(!is_removal_owner(old_next
));
934 new_node
->next
= old_next
;
936 * Here is the whole trick for lock-free replace: we add
937 * the replacement node _after_ the node we want to
938 * replace by atomically setting its next pointer at the
939 * same time we set its removal flag. Given that
940 * the lookups/get next use an iterator aware of the
941 * next pointer, they will either skip the old node due
942 * to the removal flag and see the new node, or use
943 * the old node, but will not see the new one.
944 * This is a replacement of a node with another node
945 * that has the same value: we are therefore not
946 * removing a value from the hash table. We set both the
947 * REMOVED and REMOVAL_OWNER flags atomically so we own
948 * the node after successful cmpxchg.
950 ret_next
= uatomic_cmpxchg(&old_node
->next
,
951 old_next
, flag_removed_or_removal_owner(new_node
));
952 if (ret_next
== old_next
)
953 break; /* We performed the replacement. */
958 * Ensure that the old node is not visible to readers anymore:
959 * lookup for the node, and remove it (along with any other
960 * logically removed node) if found.
962 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(old_node
->reverse_hash
));
963 _cds_lfht_gc_bucket(bucket
, new_node
);
965 assert(is_removed(CMM_LOAD_SHARED(old_node
->next
)));
970 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
971 * mode. A NULL unique_ret allows creation of duplicate keys.
974 void _cds_lfht_add(struct cds_lfht
*ht
,
976 cds_lfht_match_fct match
,
979 struct cds_lfht_node
*node
,
980 struct cds_lfht_iter
*unique_ret
,
983 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_node
, *new_next
,
985 struct cds_lfht_node
*bucket
;
987 assert(!is_bucket(node
));
988 assert(!is_removed(node
));
989 bucket
= lookup_bucket(ht
, size
, hash
);
991 uint32_t chain_len
= 0;
994 * iter_prev points to the non-removed node prior to the
998 /* We can always skip the bucket node initially */
999 iter
= rcu_dereference(iter_prev
->next
);
1000 assert(iter_prev
->reverse_hash
<= node
->reverse_hash
);
1002 if (caa_unlikely(is_end(iter
)))
1004 if (caa_likely(clear_flag(iter
)->reverse_hash
> node
->reverse_hash
))
1007 /* bucket node is the first node of the identical-hash-value chain */
1008 if (bucket_flag
&& clear_flag(iter
)->reverse_hash
== node
->reverse_hash
)
1011 next
= rcu_dereference(clear_flag(iter
)->next
);
1012 if (caa_unlikely(is_removed(next
)))
1018 && clear_flag(iter
)->reverse_hash
== node
->reverse_hash
) {
1019 struct cds_lfht_iter d_iter
= { .node
= node
, .next
= iter
, };
1022 * uniquely adding inserts the node as the first
1023 * node of the identical-hash-value node chain.
1025 * This semantic ensures no duplicated keys
1026 * should ever be observable in the table
1027 * (including traversing the table node by
1028 * node by forward iterations)
1030 cds_lfht_next_duplicate(ht
, match
, key
, &d_iter
);
1034 *unique_ret
= d_iter
;
1038 /* Only account for identical reverse hash once */
1039 if (iter_prev
->reverse_hash
!= clear_flag(iter
)->reverse_hash
1040 && !is_bucket(next
))
1041 check_resize(ht
, size
, ++chain_len
);
1042 iter_prev
= clear_flag(iter
);
1047 assert(node
!= clear_flag(iter
));
1048 assert(!is_removed(iter_prev
));
1049 assert(!is_removed(iter
));
1050 assert(iter_prev
!= node
);
1052 node
->next
= clear_flag(iter
);
1054 node
->next
= flag_bucket(clear_flag(iter
));
1055 if (is_bucket(iter
))
1056 new_node
= flag_bucket(node
);
1059 if (uatomic_cmpxchg(&iter_prev
->next
, iter
,
1060 new_node
) != iter
) {
1061 continue; /* retry */
1068 assert(!is_removed(iter
));
1069 if (is_bucket(iter
))
1070 new_next
= flag_bucket(clear_flag(next
));
1072 new_next
= clear_flag(next
);
1073 (void) uatomic_cmpxchg(&iter_prev
->next
, iter
, new_next
);
1078 unique_ret
->node
= return_node
;
1079 /* unique_ret->next left unset, never used. */
1084 int _cds_lfht_del(struct cds_lfht
*ht
, unsigned long size
,
1085 struct cds_lfht_node
*node
)
1087 struct cds_lfht_node
*bucket
, *next
;
1089 if (!node
) /* Return -ENOENT if asked to delete NULL node */
1092 /* logically delete the node */
1093 assert(!is_bucket(node
));
1094 assert(!is_removed(node
));
1095 assert(!is_removal_owner(node
));
1098 * We are first checking if the node had previously been
1099 * logically removed (this check is not atomic with setting the
1100 * logical removal flag). Return -ENOENT if the node had
1101 * previously been removed.
1103 next
= CMM_LOAD_SHARED(node
->next
); /* next is not dereferenced */
1104 if (caa_unlikely(is_removed(next
)))
1106 assert(!is_bucket(next
));
1108 * The del operation semantic guarantees a full memory barrier
1109 * before the uatomic_or atomic commit of the deletion flag.
1111 cmm_smp_mb__before_uatomic_or();
1113 * We set the REMOVED_FLAG unconditionally. Note that there may
1114 * be more than one concurrent thread setting this flag.
1115 * Knowing which wins the race will be known after the garbage
1116 * collection phase, stay tuned!
1118 uatomic_or(&node
->next
, REMOVED_FLAG
);
1119 /* We performed the (logical) deletion. */
1122 * Ensure that the node is not visible to readers anymore: lookup for
1123 * the node, and remove it (along with any other logically removed node)
1126 bucket
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->reverse_hash
));
1127 _cds_lfht_gc_bucket(bucket
, node
);
1129 assert(is_removed(CMM_LOAD_SHARED(node
->next
)));
1131 * Last phase: atomically exchange node->next with a version
1132 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
1133 * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
1134 * the node and win the removal race.
1135 * It is interesting to note that all "add" paths are forbidden
1136 * to change the next pointer starting from the point where the
1137 * REMOVED_FLAG is set, so here using a read, followed by a
1138 * xchg() suffice to guarantee that the xchg() will ever only
1139 * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
1142 if (!is_removal_owner(uatomic_xchg(&node
->next
,
1143 flag_removal_owner(node
->next
))))
1150 void *partition_resize_thread(void *arg
)
1152 struct partition_resize_work
*work
= arg
;
1154 work
->ht
->flavor
->register_thread();
1155 work
->fct(work
->ht
, work
->i
, work
->start
, work
->len
);
1156 work
->ht
->flavor
->unregister_thread();
1161 void partition_resize_helper(struct cds_lfht
*ht
, unsigned long i
,
1163 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
1164 unsigned long start
, unsigned long len
))
1166 unsigned long partition_len
;
1167 struct partition_resize_work
*work
;
1169 unsigned long nr_threads
;
1172 * Note: nr_cpus_mask + 1 is always power of 2.
1173 * We spawn just the number of threads we need to satisfy the minimum
1174 * partition size, up to the number of CPUs in the system.
1176 if (nr_cpus_mask
> 0) {
1177 nr_threads
= min(nr_cpus_mask
+ 1,
1178 len
>> MIN_PARTITION_PER_THREAD_ORDER
);
1182 partition_len
= len
>> cds_lfht_get_count_order_ulong(nr_threads
);
1183 work
= calloc(nr_threads
, sizeof(*work
));
1185 for (thread
= 0; thread
< nr_threads
; thread
++) {
1186 work
[thread
].ht
= ht
;
1188 work
[thread
].len
= partition_len
;
1189 work
[thread
].start
= thread
* partition_len
;
1190 work
[thread
].fct
= fct
;
1191 ret
= pthread_create(&(work
[thread
].thread_id
), ht
->resize_attr
,
1192 partition_resize_thread
, &work
[thread
]);
1195 for (thread
= 0; thread
< nr_threads
; thread
++) {
1196 ret
= pthread_join(work
[thread
].thread_id
, NULL
);
1203 * Holding RCU read lock to protect _cds_lfht_add against memory
1204 * reclaim that could be performed by other call_rcu worker threads (ABA
1207 * When we reach a certain length, we can split this population phase over
1208 * many worker threads, based on the number of CPUs available in the system.
1209 * This should therefore take care of not having the expand lagging behind too
1210 * many concurrent insertion threads by using the scheduler's ability to
1211 * schedule bucket node population fairly with insertions.
1214 void init_table_populate_partition(struct cds_lfht
*ht
, unsigned long i
,
1215 unsigned long start
, unsigned long len
)
1217 unsigned long j
, size
= 1UL << (i
- 1);
1219 assert(i
> MIN_TABLE_ORDER
);
1220 ht
->flavor
->read_lock();
1221 for (j
= size
+ start
; j
< size
+ start
+ len
; j
++) {
1222 struct cds_lfht_node
*new_node
= bucket_at(ht
, j
);
1224 assert(j
>= size
&& j
< (size
<< 1));
1225 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1227 new_node
->reverse_hash
= bit_reverse_ulong(j
);
1228 _cds_lfht_add(ht
, j
, NULL
, NULL
, size
, new_node
, NULL
, 1);
1230 ht
->flavor
->read_unlock();
1234 void init_table_populate(struct cds_lfht
*ht
, unsigned long i
,
1237 assert(nr_cpus_mask
!= -1);
1238 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1239 ht
->flavor
->thread_online();
1240 init_table_populate_partition(ht
, i
, 0, len
);
1241 ht
->flavor
->thread_offline();
1244 partition_resize_helper(ht
, i
, len
, init_table_populate_partition
);
1248 void init_table(struct cds_lfht
*ht
,
1249 unsigned long first_order
, unsigned long last_order
)
1253 dbg_printf("init table: first_order %lu last_order %lu\n",
1254 first_order
, last_order
);
1255 assert(first_order
> MIN_TABLE_ORDER
);
1256 for (i
= first_order
; i
<= last_order
; i
++) {
1259 len
= 1UL << (i
- 1);
1260 dbg_printf("init order %lu len: %lu\n", i
, len
);
1262 /* Stop expand if the resize target changes under us */
1263 if (CMM_LOAD_SHARED(ht
->resize_target
) < (1UL << i
))
1266 cds_lfht_alloc_bucket_table(ht
, i
);
1269 * Set all bucket nodes reverse hash values for a level and
1270 * link all bucket nodes into the table.
1272 init_table_populate(ht
, i
, len
);
1275 * Update table size.
1277 cmm_smp_wmb(); /* populate data before RCU size */
1278 CMM_STORE_SHARED(ht
->size
, 1UL << i
);
1280 dbg_printf("init new size: %lu\n", 1UL << i
);
1281 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1287 * Holding RCU read lock to protect _cds_lfht_remove against memory
1288 * reclaim that could be performed by other call_rcu worker threads (ABA
1290 * For a single level, we logically remove and garbage collect each node.
1292 * As a design choice, we perform logical removal and garbage collection on a
1293 * node-per-node basis to simplify this algorithm. We also assume keeping good
1294 * cache locality of the operation would overweight possible performance gain
1295 * that could be achieved by batching garbage collection for multiple levels.
1296 * However, this would have to be justified by benchmarks.
1298 * Concurrent removal and add operations are helping us perform garbage
1299 * collection of logically removed nodes. We guarantee that all logically
1300 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1301 * invoked to free a hole level of bucket nodes (after a grace period).
1303 * Logical removal and garbage collection can therefore be done in batch
1304 * or on a node-per-node basis, as long as the guarantee above holds.
1306 * When we reach a certain length, we can split this removal over many worker
1307 * threads, based on the number of CPUs available in the system. This should
1308 * take care of not letting resize process lag behind too many concurrent
1309 * updater threads actively inserting into the hash table.
1312 void remove_table_partition(struct cds_lfht
*ht
, unsigned long i
,
1313 unsigned long start
, unsigned long len
)
1315 unsigned long j
, size
= 1UL << (i
- 1);
1317 assert(i
> MIN_TABLE_ORDER
);
1318 ht
->flavor
->read_lock();
1319 for (j
= size
+ start
; j
< size
+ start
+ len
; j
++) {
1320 struct cds_lfht_node
*fini_bucket
= bucket_at(ht
, j
);
1321 struct cds_lfht_node
*parent_bucket
= bucket_at(ht
, j
- size
);
1323 assert(j
>= size
&& j
< (size
<< 1));
1324 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1326 /* Set the REMOVED_FLAG to freeze the ->next for gc */
1327 uatomic_or(&fini_bucket
->next
, REMOVED_FLAG
);
1328 _cds_lfht_gc_bucket(parent_bucket
, fini_bucket
);
1330 ht
->flavor
->read_unlock();
1334 void remove_table(struct cds_lfht
*ht
, unsigned long i
, unsigned long len
)
1337 assert(nr_cpus_mask
!= -1);
1338 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1339 ht
->flavor
->thread_online();
1340 remove_table_partition(ht
, i
, 0, len
);
1341 ht
->flavor
->thread_offline();
1344 partition_resize_helper(ht
, i
, len
, remove_table_partition
);
1348 * fini_table() is never called for first_order == 0, which is why
1349 * free_by_rcu_order == 0 can be used as criterion to know if free must
1353 void fini_table(struct cds_lfht
*ht
,
1354 unsigned long first_order
, unsigned long last_order
)
1357 unsigned long free_by_rcu_order
= 0;
1359 dbg_printf("fini table: first_order %lu last_order %lu\n",
1360 first_order
, last_order
);
1361 assert(first_order
> MIN_TABLE_ORDER
);
1362 for (i
= last_order
; i
>= first_order
; i
--) {
1365 len
= 1UL << (i
- 1);
1366 dbg_printf("fini order %lu len: %lu\n", i
, len
);
1368 /* Stop shrink if the resize target changes under us */
1369 if (CMM_LOAD_SHARED(ht
->resize_target
) > (1UL << (i
- 1)))
1372 cmm_smp_wmb(); /* populate data before RCU size */
1373 CMM_STORE_SHARED(ht
->size
, 1UL << (i
- 1));
1376 * We need to wait for all add operations to reach Q.S. (and
1377 * thus use the new table for lookups) before we can start
1378 * releasing the old bucket nodes. Otherwise their lookup will
1379 * return a logically removed node as insert position.
1381 ht
->flavor
->update_synchronize_rcu();
1382 if (free_by_rcu_order
)
1383 cds_lfht_free_bucket_table(ht
, free_by_rcu_order
);
1386 * Set "removed" flag in bucket nodes about to be removed.
1387 * Unlink all now-logically-removed bucket node pointers.
1388 * Concurrent add/remove operation are helping us doing
1391 remove_table(ht
, i
, len
);
1393 free_by_rcu_order
= i
;
1395 dbg_printf("fini new size: %lu\n", 1UL << i
);
1396 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1400 if (free_by_rcu_order
) {
1401 ht
->flavor
->update_synchronize_rcu();
1402 cds_lfht_free_bucket_table(ht
, free_by_rcu_order
);
1407 void cds_lfht_create_bucket(struct cds_lfht
*ht
, unsigned long size
)
1409 struct cds_lfht_node
*prev
, *node
;
1410 unsigned long order
, len
, i
;
1412 cds_lfht_alloc_bucket_table(ht
, 0);
1414 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1415 node
= bucket_at(ht
, 0);
1416 node
->next
= flag_bucket(get_end());
1417 node
->reverse_hash
= 0;
1419 for (order
= 1; order
< cds_lfht_get_count_order_ulong(size
) + 1; order
++) {
1420 len
= 1UL << (order
- 1);
1421 cds_lfht_alloc_bucket_table(ht
, order
);
1423 for (i
= 0; i
< len
; i
++) {
1425 * Now, we are trying to init the node with the
1426 * hash=(len+i) (which is also a bucket with the
1427 * index=(len+i)) and insert it into the hash table,
1428 * so this node has to be inserted after the bucket
1429 * with the index=(len+i)&(len-1)=i. And because there
1430 * is no other non-bucket node nor bucket node with
1431 * larger index/hash inserted, so the bucket node
1432 * being inserted should be inserted directly linked
1433 * after the bucket node with index=i.
1435 prev
= bucket_at(ht
, i
);
1436 node
= bucket_at(ht
, len
+ i
);
1438 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1439 order
, len
+ i
, len
+ i
);
1440 node
->reverse_hash
= bit_reverse_ulong(len
+ i
);
1442 /* insert after prev */
1443 assert(is_bucket(prev
->next
));
1444 node
->next
= prev
->next
;
1445 prev
->next
= flag_bucket(node
);
1450 struct cds_lfht
*_cds_lfht_new(unsigned long init_size
,
1451 unsigned long min_nr_alloc_buckets
,
1452 unsigned long max_nr_buckets
,
1454 const struct cds_lfht_mm_type
*mm
,
1455 const struct rcu_flavor_struct
*flavor
,
1456 pthread_attr_t
*attr
)
1458 struct cds_lfht
*ht
;
1459 unsigned long order
;
1461 /* min_nr_alloc_buckets must be power of two */
1462 if (!min_nr_alloc_buckets
|| (min_nr_alloc_buckets
& (min_nr_alloc_buckets
- 1)))
1465 /* init_size must be power of two */
1466 if (!init_size
|| (init_size
& (init_size
- 1)))
1470 * Memory management plugin default.
1473 if (CAA_BITS_PER_LONG
> 32
1475 && max_nr_buckets
<= (1ULL << 32)) {
1477 * For 64-bit architectures, with max number of
1478 * buckets small enough not to use the entire
1479 * 64-bit memory mapping space (and allowing a
1480 * fair number of hash table instances), use the
1481 * mmap allocator, which is faster than the
1484 mm
= &cds_lfht_mm_mmap
;
1487 * The fallback is to use the order allocator.
1489 mm
= &cds_lfht_mm_order
;
1493 /* max_nr_buckets == 0 for order based mm means infinite */
1494 if (mm
== &cds_lfht_mm_order
&& !max_nr_buckets
)
1495 max_nr_buckets
= 1UL << (MAX_TABLE_ORDER
- 1);
1497 /* max_nr_buckets must be power of two */
1498 if (!max_nr_buckets
|| (max_nr_buckets
& (max_nr_buckets
- 1)))
1501 min_nr_alloc_buckets
= max(min_nr_alloc_buckets
, MIN_TABLE_SIZE
);
1502 init_size
= max(init_size
, MIN_TABLE_SIZE
);
1503 max_nr_buckets
= max(max_nr_buckets
, min_nr_alloc_buckets
);
1504 init_size
= min(init_size
, max_nr_buckets
);
1506 ht
= mm
->alloc_cds_lfht(min_nr_alloc_buckets
, max_nr_buckets
);
1508 assert(ht
->mm
== mm
);
1509 assert(ht
->bucket_at
== mm
->bucket_at
);
1512 ht
->flavor
= flavor
;
1513 ht
->resize_attr
= attr
;
1514 alloc_split_items_count(ht
);
1515 /* this mutex should not nest in read-side C.S. */
1516 pthread_mutex_init(&ht
->resize_mutex
, NULL
);
1517 order
= cds_lfht_get_count_order_ulong(init_size
);
1518 ht
->resize_target
= 1UL << order
;
1519 cds_lfht_create_bucket(ht
, 1UL << order
);
1520 ht
->size
= 1UL << order
;
1524 void cds_lfht_lookup(struct cds_lfht
*ht
, unsigned long hash
,
1525 cds_lfht_match_fct match
, const void *key
,
1526 struct cds_lfht_iter
*iter
)
1528 struct cds_lfht_node
*node
, *next
, *bucket
;
1529 unsigned long reverse_hash
, size
;
1531 reverse_hash
= bit_reverse_ulong(hash
);
1533 size
= rcu_dereference(ht
->size
);
1534 bucket
= lookup_bucket(ht
, size
, hash
);
1535 /* We can always skip the bucket node initially */
1536 node
= rcu_dereference(bucket
->next
);
1537 node
= clear_flag(node
);
1539 if (caa_unlikely(is_end(node
))) {
1543 if (caa_unlikely(node
->reverse_hash
> reverse_hash
)) {
1547 next
= rcu_dereference(node
->next
);
1548 assert(node
== clear_flag(node
));
1549 if (caa_likely(!is_removed(next
))
1551 && node
->reverse_hash
== reverse_hash
1552 && caa_likely(match(node
, key
))) {
1555 node
= clear_flag(next
);
1557 assert(!node
|| !is_bucket(CMM_LOAD_SHARED(node
->next
)));
1562 void cds_lfht_next_duplicate(struct cds_lfht
*ht
, cds_lfht_match_fct match
,
1563 const void *key
, struct cds_lfht_iter
*iter
)
1565 struct cds_lfht_node
*node
, *next
;
1566 unsigned long reverse_hash
;
1569 reverse_hash
= node
->reverse_hash
;
1571 node
= clear_flag(next
);
1574 if (caa_unlikely(is_end(node
))) {
1578 if (caa_unlikely(node
->reverse_hash
> reverse_hash
)) {
1582 next
= rcu_dereference(node
->next
);
1583 if (caa_likely(!is_removed(next
))
1585 && caa_likely(match(node
, key
))) {
1588 node
= clear_flag(next
);
1590 assert(!node
|| !is_bucket(CMM_LOAD_SHARED(node
->next
)));
1595 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1597 struct cds_lfht_node
*node
, *next
;
1599 node
= clear_flag(iter
->next
);
1601 if (caa_unlikely(is_end(node
))) {
1605 next
= rcu_dereference(node
->next
);
1606 if (caa_likely(!is_removed(next
))
1607 && !is_bucket(next
)) {
1610 node
= clear_flag(next
);
1612 assert(!node
|| !is_bucket(CMM_LOAD_SHARED(node
->next
)));
1617 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1620 * Get next after first bucket node. The first bucket node is the
1621 * first node of the linked list.
1623 iter
->next
= bucket_at(ht
, 0)->next
;
1624 cds_lfht_next(ht
, iter
);
1627 void cds_lfht_add(struct cds_lfht
*ht
, unsigned long hash
,
1628 struct cds_lfht_node
*node
)
1632 node
->reverse_hash
= bit_reverse_ulong(hash
);
1633 size
= rcu_dereference(ht
->size
);
1634 _cds_lfht_add(ht
, hash
, NULL
, NULL
, size
, node
, NULL
, 0);
1635 ht_count_add(ht
, size
, hash
);
1638 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
1640 cds_lfht_match_fct match
,
1642 struct cds_lfht_node
*node
)
1645 struct cds_lfht_iter iter
;
1647 node
->reverse_hash
= bit_reverse_ulong(hash
);
1648 size
= rcu_dereference(ht
->size
);
1649 _cds_lfht_add(ht
, hash
, match
, key
, size
, node
, &iter
, 0);
1650 if (iter
.node
== node
)
1651 ht_count_add(ht
, size
, hash
);
1655 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
1657 cds_lfht_match_fct match
,
1659 struct cds_lfht_node
*node
)
1662 struct cds_lfht_iter iter
;
1664 node
->reverse_hash
= bit_reverse_ulong(hash
);
1665 size
= rcu_dereference(ht
->size
);
1667 _cds_lfht_add(ht
, hash
, match
, key
, size
, node
, &iter
, 0);
1668 if (iter
.node
== node
) {
1669 ht_count_add(ht
, size
, hash
);
1673 if (!_cds_lfht_replace(ht
, size
, iter
.node
, iter
.next
, node
))
1678 int cds_lfht_replace(struct cds_lfht
*ht
,
1679 struct cds_lfht_iter
*old_iter
,
1681 cds_lfht_match_fct match
,
1683 struct cds_lfht_node
*new_node
)
1687 new_node
->reverse_hash
= bit_reverse_ulong(hash
);
1688 if (!old_iter
->node
)
1690 if (caa_unlikely(old_iter
->node
->reverse_hash
!= new_node
->reverse_hash
))
1692 if (caa_unlikely(!match(old_iter
->node
, key
)))
1694 size
= rcu_dereference(ht
->size
);
1695 return _cds_lfht_replace(ht
, size
, old_iter
->node
, old_iter
->next
,
1699 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_node
*node
)
1701 unsigned long size
, hash
;
1704 size
= rcu_dereference(ht
->size
);
1705 ret
= _cds_lfht_del(ht
, size
, node
);
1707 hash
= bit_reverse_ulong(node
->reverse_hash
);
1708 ht_count_del(ht
, size
, hash
);
1713 int cds_lfht_is_node_deleted(struct cds_lfht_node
*node
)
1715 return is_removed(CMM_LOAD_SHARED(node
->next
));
1719 int cds_lfht_delete_bucket(struct cds_lfht
*ht
)
1721 struct cds_lfht_node
*node
;
1722 unsigned long order
, i
, size
;
1724 /* Check that the table is empty */
1725 node
= bucket_at(ht
, 0);
1727 node
= clear_flag(node
)->next
;
1728 if (!is_bucket(node
))
1730 assert(!is_removed(node
));
1731 } while (!is_end(node
));
1733 * size accessed without rcu_dereference because hash table is
1737 /* Internal sanity check: all nodes left should be buckets */
1738 for (i
= 0; i
< size
; i
++) {
1739 node
= bucket_at(ht
, i
);
1740 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1741 i
, i
, bit_reverse_ulong(node
->reverse_hash
));
1742 assert(is_bucket(node
->next
));
1745 for (order
= cds_lfht_get_count_order_ulong(size
); (long)order
>= 0; order
--)
1746 cds_lfht_free_bucket_table(ht
, order
);
1752 * Should only be called when no more concurrent readers nor writers can
1753 * possibly access the table.
1755 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
)
1758 #ifdef rcu_read_ongoing_mb
1762 /* Wait for in-flight resize operations to complete */
1763 _CMM_STORE_SHARED(ht
->in_progress_destroy
, 1);
1764 cmm_smp_mb(); /* Store destroy before load resize */
1765 #ifdef rcu_read_ongoing_mb
1766 was_online
= ht
->flavor
->read_ongoing();
1768 ht
->flavor
->thread_offline();
1769 /* Calling with RCU read-side held is an error. */
1770 if (ht
->flavor
->read_ongoing()) {
1773 ht
->flavor
->thread_online();
1777 while (uatomic_read(&ht
->in_progress_resize
))
1778 (void) poll(NULL
, 0, 100); /* wait for 100ms */
1779 ret
= cds_lfht_delete_bucket(ht
);
1782 free_split_items_count(ht
);
1784 *attr
= ht
->resize_attr
;
1786 #ifdef rcu_read_ongoing_mb
1792 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
1793 long *approx_before
,
1794 unsigned long *count
,
1797 struct cds_lfht_node
*node
, *next
;
1798 unsigned long nr_bucket
= 0, nr_removed
= 0;
1801 if (ht
->split_count
) {
1804 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1805 *approx_before
+= uatomic_read(&ht
->split_count
[i
].add
);
1806 *approx_before
-= uatomic_read(&ht
->split_count
[i
].del
);
1812 /* Count non-bucket nodes in the table */
1813 node
= bucket_at(ht
, 0);
1815 next
= rcu_dereference(node
->next
);
1816 if (is_removed(next
)) {
1817 if (!is_bucket(next
))
1821 } else if (!is_bucket(next
))
1825 node
= clear_flag(next
);
1826 } while (!is_end(node
));
1827 dbg_printf("number of logically removed nodes: %lu\n", nr_removed
);
1828 dbg_printf("number of bucket nodes: %lu\n", nr_bucket
);
1830 if (ht
->split_count
) {
1833 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1834 *approx_after
+= uatomic_read(&ht
->split_count
[i
].add
);
1835 *approx_after
-= uatomic_read(&ht
->split_count
[i
].del
);
1840 /* called with resize mutex held */
1842 void _do_cds_lfht_grow(struct cds_lfht
*ht
,
1843 unsigned long old_size
, unsigned long new_size
)
1845 unsigned long old_order
, new_order
;
1847 old_order
= cds_lfht_get_count_order_ulong(old_size
);
1848 new_order
= cds_lfht_get_count_order_ulong(new_size
);
1849 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1850 old_size
, old_order
, new_size
, new_order
);
1851 assert(new_size
> old_size
);
1852 init_table(ht
, old_order
+ 1, new_order
);
1855 /* called with resize mutex held */
1857 void _do_cds_lfht_shrink(struct cds_lfht
*ht
,
1858 unsigned long old_size
, unsigned long new_size
)
1860 unsigned long old_order
, new_order
;
1862 new_size
= max(new_size
, MIN_TABLE_SIZE
);
1863 old_order
= cds_lfht_get_count_order_ulong(old_size
);
1864 new_order
= cds_lfht_get_count_order_ulong(new_size
);
1865 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1866 old_size
, old_order
, new_size
, new_order
);
1867 assert(new_size
< old_size
);
1869 /* Remove and unlink all bucket nodes to remove. */
1870 fini_table(ht
, new_order
+ 1, old_order
);
1874 /* called with resize mutex held */
1876 void _do_cds_lfht_resize(struct cds_lfht
*ht
)
1878 unsigned long new_size
, old_size
;
1881 * Resize table, re-do if the target size has changed under us.
1884 assert(uatomic_read(&ht
->in_progress_resize
));
1885 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1887 ht
->resize_initiated
= 1;
1888 old_size
= ht
->size
;
1889 new_size
= CMM_LOAD_SHARED(ht
->resize_target
);
1890 if (old_size
< new_size
)
1891 _do_cds_lfht_grow(ht
, old_size
, new_size
);
1892 else if (old_size
> new_size
)
1893 _do_cds_lfht_shrink(ht
, old_size
, new_size
);
1894 ht
->resize_initiated
= 0;
1895 /* write resize_initiated before read resize_target */
1897 } while (ht
->size
!= CMM_LOAD_SHARED(ht
->resize_target
));
1901 unsigned long resize_target_grow(struct cds_lfht
*ht
, unsigned long new_size
)
1903 return _uatomic_xchg_monotonic_increase(&ht
->resize_target
, new_size
);
1907 void resize_target_update_count(struct cds_lfht
*ht
,
1908 unsigned long count
)
1910 count
= max(count
, MIN_TABLE_SIZE
);
1911 count
= min(count
, ht
->max_nr_buckets
);
1912 uatomic_set(&ht
->resize_target
, count
);
1915 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
)
1917 #ifdef rcu_read_ongoing_mb
1920 was_online
= ht
->flavor
->read_ongoing();
1922 ht
->flavor
->thread_offline();
1923 /* Calling with RCU read-side held is an error. */
1924 if (ht
->flavor
->read_ongoing()) {
1925 static int print_once
;
1927 if (!CMM_LOAD_SHARED(print_once
))
1928 fprintf(stderr
, "[error] rculfhash: cds_lfht_resize "
1929 "called with RCU read-side lock held.\n");
1930 CMM_STORE_SHARED(print_once
, 1);
1935 resize_target_update_count(ht
, new_size
);
1936 CMM_STORE_SHARED(ht
->resize_initiated
, 1);
1937 pthread_mutex_lock(&ht
->resize_mutex
);
1938 _do_cds_lfht_resize(ht
);
1939 pthread_mutex_unlock(&ht
->resize_mutex
);
1940 #ifdef rcu_read_ongoing_mb
1943 ht
->flavor
->thread_online();
1948 void do_resize_cb(struct rcu_head
*head
)
1950 struct rcu_resize_work
*work
=
1951 caa_container_of(head
, struct rcu_resize_work
, head
);
1952 struct cds_lfht
*ht
= work
->ht
;
1954 ht
->flavor
->thread_offline();
1955 pthread_mutex_lock(&ht
->resize_mutex
);
1956 _do_cds_lfht_resize(ht
);
1957 pthread_mutex_unlock(&ht
->resize_mutex
);
1958 ht
->flavor
->thread_online();
1960 cmm_smp_mb(); /* finish resize before decrement */
1961 uatomic_dec(&ht
->in_progress_resize
);
1965 void __cds_lfht_resize_lazy_launch(struct cds_lfht
*ht
)
1967 struct rcu_resize_work
*work
;
1969 /* Store resize_target before read resize_initiated */
1971 if (!CMM_LOAD_SHARED(ht
->resize_initiated
)) {
1972 uatomic_inc(&ht
->in_progress_resize
);
1973 cmm_smp_mb(); /* increment resize count before load destroy */
1974 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
)) {
1975 uatomic_dec(&ht
->in_progress_resize
);
1978 work
= zmalloc(sizeof(*work
));
1980 dbg_printf("error allocating resize work, bailing out\n");
1981 uatomic_dec(&ht
->in_progress_resize
);
1985 ht
->flavor
->update_call_rcu(&work
->head
, do_resize_cb
);
1986 CMM_STORE_SHARED(ht
->resize_initiated
, 1);
1991 void cds_lfht_resize_lazy_grow(struct cds_lfht
*ht
, unsigned long size
, int growth
)
1993 unsigned long target_size
= size
<< growth
;
1995 target_size
= min(target_size
, ht
->max_nr_buckets
);
1996 if (resize_target_grow(ht
, target_size
) >= target_size
)
1999 __cds_lfht_resize_lazy_launch(ht
);
2003 * We favor grow operations over shrink. A shrink operation never occurs
2004 * if a grow operation is queued for lazy execution. A grow operation
2005 * cancels any pending shrink lazy execution.
2008 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
2009 unsigned long count
)
2011 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
2013 count
= max(count
, MIN_TABLE_SIZE
);
2014 count
= min(count
, ht
->max_nr_buckets
);
2016 return; /* Already the right size, no resize needed */
2017 if (count
> size
) { /* lazy grow */
2018 if (resize_target_grow(ht
, count
) >= count
)
2020 } else { /* lazy shrink */
2024 s
= uatomic_cmpxchg(&ht
->resize_target
, size
, count
);
2026 break; /* no resize needed */
2028 return; /* growing is/(was just) in progress */
2030 return; /* some other thread do shrink */
2034 __cds_lfht_resize_lazy_launch(ht
);