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Diffstat (limited to 'contrib/jemalloc/src/ckh.c')
| -rw-r--r-- | contrib/jemalloc/src/ckh.c | 609 |
1 files changed, 609 insertions, 0 deletions
diff --git a/contrib/jemalloc/src/ckh.c b/contrib/jemalloc/src/ckh.c new file mode 100644 index 0000000..742a950 --- /dev/null +++ b/contrib/jemalloc/src/ckh.c @@ -0,0 +1,609 @@ +/* + ******************************************************************************* + * Implementation of (2^1+,2) cuckoo hashing, where 2^1+ indicates that each + * hash bucket contains 2^n cells, for n >= 1, and 2 indicates that two hash + * functions are employed. The original cuckoo hashing algorithm was described + * in: + * + * Pagh, R., F.F. Rodler (2004) Cuckoo Hashing. Journal of Algorithms + * 51(2):122-144. + * + * Generalization of cuckoo hashing was discussed in: + * + * Erlingsson, U., M. Manasse, F. McSherry (2006) A cool and practical + * alternative to traditional hash tables. In Proceedings of the 7th + * Workshop on Distributed Data and Structures (WDAS'06), Santa Clara, CA, + * January 2006. + * + * This implementation uses precisely two hash functions because that is the + * fewest that can work, and supporting multiple hashes is an implementation + * burden. Here is a reproduction of Figure 1 from Erlingsson et al. (2006) + * that shows approximate expected maximum load factors for various + * configurations: + * + * | #cells/bucket | + * #hashes | 1 | 2 | 4 | 8 | + * --------+-------+-------+-------+-------+ + * 1 | 0.006 | 0.006 | 0.03 | 0.12 | + * 2 | 0.49 | 0.86 |>0.93< |>0.96< | + * 3 | 0.91 | 0.97 | 0.98 | 0.999 | + * 4 | 0.97 | 0.99 | 0.999 | | + * + * The number of cells per bucket is chosen such that a bucket fits in one cache + * line. So, on 32- and 64-bit systems, we use (8,2) and (4,2) cuckoo hashing, + * respectively. + * + ******************************************************************************/ +#define JEMALLOC_CKH_C_ +#include "jemalloc/internal/jemalloc_internal.h" + +/******************************************************************************/ +/* Function prototypes for non-inline static functions. */ + +static bool ckh_grow(ckh_t *ckh); +static void ckh_shrink(ckh_t *ckh); + +/******************************************************************************/ + +/* + * Search bucket for key and return the cell number if found; SIZE_T_MAX + * otherwise. + */ +JEMALLOC_INLINE size_t +ckh_bucket_search(ckh_t *ckh, size_t bucket, const void *key) +{ + ckhc_t *cell; + unsigned i; + + for (i = 0; i < (ZU(1) << LG_CKH_BUCKET_CELLS); i++) { + cell = &ckh->tab[(bucket << LG_CKH_BUCKET_CELLS) + i]; + if (cell->key != NULL && ckh->keycomp(key, cell->key)) + return ((bucket << LG_CKH_BUCKET_CELLS) + i); + } + + return (SIZE_T_MAX); +} + +/* + * Search table for key and return cell number if found; SIZE_T_MAX otherwise. + */ +JEMALLOC_INLINE size_t +ckh_isearch(ckh_t *ckh, const void *key) +{ + size_t hash1, hash2, bucket, cell; + + assert(ckh != NULL); + + ckh->hash(key, ckh->lg_curbuckets, &hash1, &hash2); + + /* Search primary bucket. */ + bucket = hash1 & ((ZU(1) << ckh->lg_curbuckets) - 1); + cell = ckh_bucket_search(ckh, bucket, key); + if (cell != SIZE_T_MAX) + return (cell); + + /* Search secondary bucket. */ + bucket = hash2 & ((ZU(1) << ckh->lg_curbuckets) - 1); + cell = ckh_bucket_search(ckh, bucket, key); + return (cell); +} + +JEMALLOC_INLINE bool +ckh_try_bucket_insert(ckh_t *ckh, size_t bucket, const void *key, + const void *data) +{ + ckhc_t *cell; + unsigned offset, i; + + /* + * Cycle through the cells in the bucket, starting at a random position. + * The randomness avoids worst-case search overhead as buckets fill up. + */ + prng32(offset, LG_CKH_BUCKET_CELLS, ckh->prng_state, CKH_A, CKH_C); + for (i = 0; i < (ZU(1) << LG_CKH_BUCKET_CELLS); i++) { + cell = &ckh->tab[(bucket << LG_CKH_BUCKET_CELLS) + + ((i + offset) & ((ZU(1) << LG_CKH_BUCKET_CELLS) - 1))]; + if (cell->key == NULL) { + cell->key = key; + cell->data = data; + ckh->count++; + return (false); + } + } + + return (true); +} + +/* + * No space is available in bucket. Randomly evict an item, then try to find an + * alternate location for that item. Iteratively repeat this + * eviction/relocation procedure until either success or detection of an + * eviction/relocation bucket cycle. + */ +JEMALLOC_INLINE bool +ckh_evict_reloc_insert(ckh_t *ckh, size_t argbucket, void const **argkey, + void const **argdata) +{ + const void *key, *data, *tkey, *tdata; + ckhc_t *cell; + size_t hash1, hash2, bucket, tbucket; + unsigned i; + + bucket = argbucket; + key = *argkey; + data = *argdata; + while (true) { + /* + * Choose a random item within the bucket to evict. This is + * critical to correct function, because without (eventually) + * evicting all items within a bucket during iteration, it + * would be possible to get stuck in an infinite loop if there + * were an item for which both hashes indicated the same + * bucket. + */ + prng32(i, LG_CKH_BUCKET_CELLS, ckh->prng_state, CKH_A, CKH_C); + cell = &ckh->tab[(bucket << LG_CKH_BUCKET_CELLS) + i]; + assert(cell->key != NULL); + + /* Swap cell->{key,data} and {key,data} (evict). */ + tkey = cell->key; tdata = cell->data; + cell->key = key; cell->data = data; + key = tkey; data = tdata; + +#ifdef CKH_COUNT + ckh->nrelocs++; +#endif + + /* Find the alternate bucket for the evicted item. */ + ckh->hash(key, ckh->lg_curbuckets, &hash1, &hash2); + tbucket = hash2 & ((ZU(1) << ckh->lg_curbuckets) - 1); + if (tbucket == bucket) { + tbucket = hash1 & ((ZU(1) << ckh->lg_curbuckets) - 1); + /* + * It may be that (tbucket == bucket) still, if the + * item's hashes both indicate this bucket. However, + * we are guaranteed to eventually escape this bucket + * during iteration, assuming pseudo-random item + * selection (true randomness would make infinite + * looping a remote possibility). The reason we can + * never get trapped forever is that there are two + * cases: + * + * 1) This bucket == argbucket, so we will quickly + * detect an eviction cycle and terminate. + * 2) An item was evicted to this bucket from another, + * which means that at least one item in this bucket + * has hashes that indicate distinct buckets. + */ + } + /* Check for a cycle. */ + if (tbucket == argbucket) { + *argkey = key; + *argdata = data; + return (true); + } + + bucket = tbucket; + if (ckh_try_bucket_insert(ckh, bucket, key, data) == false) + return (false); + } +} + +JEMALLOC_INLINE bool +ckh_try_insert(ckh_t *ckh, void const**argkey, void const**argdata) +{ + size_t hash1, hash2, bucket; + const void *key = *argkey; + const void *data = *argdata; + + ckh->hash(key, ckh->lg_curbuckets, &hash1, &hash2); + + /* Try to insert in primary bucket. */ + bucket = hash1 & ((ZU(1) << ckh->lg_curbuckets) - 1); + if (ckh_try_bucket_insert(ckh, bucket, key, data) == false) + return (false); + + /* Try to insert in secondary bucket. */ + bucket = hash2 & ((ZU(1) << ckh->lg_curbuckets) - 1); + if (ckh_try_bucket_insert(ckh, bucket, key, data) == false) + return (false); + + /* + * Try to find a place for this item via iterative eviction/relocation. + */ + return (ckh_evict_reloc_insert(ckh, bucket, argkey, argdata)); +} + +/* + * Try to rebuild the hash table from scratch by inserting all items from the + * old table into the new. + */ +JEMALLOC_INLINE bool +ckh_rebuild(ckh_t *ckh, ckhc_t *aTab) +{ + size_t count, i, nins; + const void *key, *data; + + count = ckh->count; + ckh->count = 0; + for (i = nins = 0; nins < count; i++) { + if (aTab[i].key != NULL) { + key = aTab[i].key; + data = aTab[i].data; + if (ckh_try_insert(ckh, &key, &data)) { + ckh->count = count; + return (true); + } + nins++; + } + } + + return (false); +} + +static bool +ckh_grow(ckh_t *ckh) +{ + bool ret; + ckhc_t *tab, *ttab; + size_t lg_curcells; + unsigned lg_prevbuckets; + +#ifdef CKH_COUNT + ckh->ngrows++; +#endif + + /* + * It is possible (though unlikely, given well behaved hashes) that the + * table will have to be doubled more than once in order to create a + * usable table. + */ + lg_prevbuckets = ckh->lg_curbuckets; + lg_curcells = ckh->lg_curbuckets + LG_CKH_BUCKET_CELLS; + while (true) { + size_t usize; + + lg_curcells++; + usize = sa2u(sizeof(ckhc_t) << lg_curcells, CACHELINE); + if (usize == 0) { + ret = true; + goto label_return; + } + tab = (ckhc_t *)ipalloc(usize, CACHELINE, true); + if (tab == NULL) { + ret = true; + goto label_return; + } + /* Swap in new table. */ + ttab = ckh->tab; + ckh->tab = tab; + tab = ttab; + ckh->lg_curbuckets = lg_curcells - LG_CKH_BUCKET_CELLS; + + if (ckh_rebuild(ckh, tab) == false) { + idalloc(tab); + break; + } + + /* Rebuilding failed, so back out partially rebuilt table. */ + idalloc(ckh->tab); + ckh->tab = tab; + ckh->lg_curbuckets = lg_prevbuckets; + } + + ret = false; +label_return: + return (ret); +} + +static void +ckh_shrink(ckh_t *ckh) +{ + ckhc_t *tab, *ttab; + size_t lg_curcells, usize; + unsigned lg_prevbuckets; + + /* + * It is possible (though unlikely, given well behaved hashes) that the + * table rebuild will fail. + */ + lg_prevbuckets = ckh->lg_curbuckets; + lg_curcells = ckh->lg_curbuckets + LG_CKH_BUCKET_CELLS - 1; + usize = sa2u(sizeof(ckhc_t) << lg_curcells, CACHELINE); + if (usize == 0) + return; + tab = (ckhc_t *)ipalloc(usize, CACHELINE, true); + if (tab == NULL) { + /* + * An OOM error isn't worth propagating, since it doesn't + * prevent this or future operations from proceeding. + */ + return; + } + /* Swap in new table. */ + ttab = ckh->tab; + ckh->tab = tab; + tab = ttab; + ckh->lg_curbuckets = lg_curcells - LG_CKH_BUCKET_CELLS; + + if (ckh_rebuild(ckh, tab) == false) { + idalloc(tab); +#ifdef CKH_COUNT + ckh->nshrinks++; +#endif + return; + } + + /* Rebuilding failed, so back out partially rebuilt table. */ + idalloc(ckh->tab); + ckh->tab = tab; + ckh->lg_curbuckets = lg_prevbuckets; +#ifdef CKH_COUNT + ckh->nshrinkfails++; +#endif +} + +bool +ckh_new(ckh_t *ckh, size_t minitems, ckh_hash_t *hash, ckh_keycomp_t *keycomp) +{ + bool ret; + size_t mincells, usize; + unsigned lg_mincells; + + assert(minitems > 0); + assert(hash != NULL); + assert(keycomp != NULL); + +#ifdef CKH_COUNT + ckh->ngrows = 0; + ckh->nshrinks = 0; + ckh->nshrinkfails = 0; + ckh->ninserts = 0; + ckh->nrelocs = 0; +#endif + ckh->prng_state = 42; /* Value doesn't really matter. */ + ckh->count = 0; + + /* + * Find the minimum power of 2 that is large enough to fit aBaseCount + * entries. We are using (2+,2) cuckoo hashing, which has an expected + * maximum load factor of at least ~0.86, so 0.75 is a conservative load + * factor that will typically allow 2^aLgMinItems to fit without ever + * growing the table. + */ + assert(LG_CKH_BUCKET_CELLS > 0); + mincells = ((minitems + (3 - (minitems % 3))) / 3) << 2; + for (lg_mincells = LG_CKH_BUCKET_CELLS; + (ZU(1) << lg_mincells) < mincells; + lg_mincells++) + ; /* Do nothing. */ + ckh->lg_minbuckets = lg_mincells - LG_CKH_BUCKET_CELLS; + ckh->lg_curbuckets = lg_mincells - LG_CKH_BUCKET_CELLS; + ckh->hash = hash; + ckh->keycomp = keycomp; + + usize = sa2u(sizeof(ckhc_t) << lg_mincells, CACHELINE); + if (usize == 0) { + ret = true; + goto label_return; + } + ckh->tab = (ckhc_t *)ipalloc(usize, CACHELINE, true); + if (ckh->tab == NULL) { + ret = true; + goto label_return; + } + + ret = false; +label_return: + return (ret); +} + +void +ckh_delete(ckh_t *ckh) +{ + + assert(ckh != NULL); + +#ifdef CKH_VERBOSE + malloc_printf( + "%s(%p): ngrows: %"PRIu64", nshrinks: %"PRIu64"," + " nshrinkfails: %"PRIu64", ninserts: %"PRIu64"," + " nrelocs: %"PRIu64"\n", __func__, ckh, + (unsigned long long)ckh->ngrows, + (unsigned long long)ckh->nshrinks, + (unsigned long long)ckh->nshrinkfails, + (unsigned long long)ckh->ninserts, + (unsigned long long)ckh->nrelocs); +#endif + + idalloc(ckh->tab); +#ifdef JEMALLOC_DEBUG + memset(ckh, 0x5a, sizeof(ckh_t)); +#endif +} + +size_t +ckh_count(ckh_t *ckh) +{ + + assert(ckh != NULL); + + return (ckh->count); +} + +bool +ckh_iter(ckh_t *ckh, size_t *tabind, void **key, void **data) +{ + size_t i, ncells; + + for (i = *tabind, ncells = (ZU(1) << (ckh->lg_curbuckets + + LG_CKH_BUCKET_CELLS)); i < ncells; i++) { + if (ckh->tab[i].key != NULL) { + if (key != NULL) + *key = (void *)ckh->tab[i].key; + if (data != NULL) + *data = (void *)ckh->tab[i].data; + *tabind = i + 1; + return (false); + } + } + + return (true); +} + +bool +ckh_insert(ckh_t *ckh, const void *key, const void *data) +{ + bool ret; + + assert(ckh != NULL); + assert(ckh_search(ckh, key, NULL, NULL)); + +#ifdef CKH_COUNT + ckh->ninserts++; +#endif + + while (ckh_try_insert(ckh, &key, &data)) { + if (ckh_grow(ckh)) { + ret = true; + goto label_return; + } + } + + ret = false; +label_return: + return (ret); +} + +bool +ckh_remove(ckh_t *ckh, const void *searchkey, void **key, void **data) +{ + size_t cell; + + assert(ckh != NULL); + + cell = ckh_isearch(ckh, searchkey); + if (cell != SIZE_T_MAX) { + if (key != NULL) + *key = (void *)ckh->tab[cell].key; + if (data != NULL) + *data = (void *)ckh->tab[cell].data; + ckh->tab[cell].key = NULL; + ckh->tab[cell].data = NULL; /* Not necessary. */ + + ckh->count--; + /* Try to halve the table if it is less than 1/4 full. */ + if (ckh->count < (ZU(1) << (ckh->lg_curbuckets + + LG_CKH_BUCKET_CELLS - 2)) && ckh->lg_curbuckets + > ckh->lg_minbuckets) { + /* Ignore error due to OOM. */ + ckh_shrink(ckh); + } + + return (false); + } + + return (true); +} + +bool +ckh_search(ckh_t *ckh, const void *searchkey, void **key, void **data) +{ + size_t cell; + + assert(ckh != NULL); + + cell = ckh_isearch(ckh, searchkey); + if (cell != SIZE_T_MAX) { + if (key != NULL) + *key = (void *)ckh->tab[cell].key; + if (data != NULL) + *data = (void *)ckh->tab[cell].data; + return (false); + } + + return (true); +} + +void +ckh_string_hash(const void *key, unsigned minbits, size_t *hash1, size_t *hash2) +{ + size_t ret1, ret2; + uint64_t h; + + assert(minbits <= 32 || (SIZEOF_PTR == 8 && minbits <= 64)); + assert(hash1 != NULL); + assert(hash2 != NULL); + + h = hash(key, strlen((const char *)key), UINT64_C(0x94122f335b332aea)); + if (minbits <= 32) { + /* + * Avoid doing multiple hashes, since a single hash provides + * enough bits. + */ + ret1 = h & ZU(0xffffffffU); + ret2 = h >> 32; + } else { + ret1 = h; + ret2 = hash(key, strlen((const char *)key), + UINT64_C(0x8432a476666bbc13)); + } + + *hash1 = ret1; + *hash2 = ret2; +} + +bool +ckh_string_keycomp(const void *k1, const void *k2) +{ + + assert(k1 != NULL); + assert(k2 != NULL); + + return (strcmp((char *)k1, (char *)k2) ? false : true); +} + +void +ckh_pointer_hash(const void *key, unsigned minbits, size_t *hash1, + size_t *hash2) +{ + size_t ret1, ret2; + uint64_t h; + union { + const void *v; + uint64_t i; + } u; + + assert(minbits <= 32 || (SIZEOF_PTR == 8 && minbits <= 64)); + assert(hash1 != NULL); + assert(hash2 != NULL); + + assert(sizeof(u.v) == sizeof(u.i)); +#if (LG_SIZEOF_PTR != LG_SIZEOF_INT) + u.i = 0; +#endif + u.v = key; + h = hash(&u.i, sizeof(u.i), UINT64_C(0xd983396e68886082)); + if (minbits <= 32) { + /* + * Avoid doing multiple hashes, since a single hash provides + * enough bits. + */ + ret1 = h & ZU(0xffffffffU); + ret2 = h >> 32; + } else { + assert(SIZEOF_PTR == 8); + ret1 = h; + ret2 = hash(&u.i, sizeof(u.i), UINT64_C(0x5e2be9aff8709a5d)); + } + + *hash1 = ret1; + *hash2 = ret2; +} + +bool +ckh_pointer_keycomp(const void *k1, const void *k2) +{ + + return ((k1 == k2) ? true : false); +} |
