static bool
ckh_try_insert(ckh_t *ckh, void const**argkey, void const**argdata) {
size_t hashes[2], bucket;
const void *key = *argkey;
const void *data = *argdata;
ckh->hash(key, hashes);
/* Try to insert in primary bucket. */
bucket = hashes[0] & ((ZU(1) << ckh->lg_curbuckets) - 1);
if (!ckh_try_bucket_insert(ckh, bucket, key, data)) {
return false;
}
/* Try to insert in secondary bucket. */
bucket = hashes[1] & ((ZU(1) << ckh->lg_curbuckets) - 1);
if (!ckh_try_bucket_insert(ckh, bucket, key, data)) {
return false;
}
/*
* Try to find a place for this item via iterative eviction/relocation.
*/
return ckh_evict_reloc_insert(ckh, bucket, argkey, argdata);
}
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));
}
/*
* 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 hashes[2], 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, hashes);
tbucket = hashes[1] & ((ZU(1) << ckh->lg_curbuckets) - 1);
if (tbucket == bucket) {
tbucket = hashes[0] & ((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);
}
}