- /*
+ /*
Trivial Database 2: hash handling
Copyright (C) Rusty Russell 2010
-
+
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
uint64_t hash_record(struct tdb_context *tdb, tdb_off_t off)
{
- struct tdb_used_record pad, *r;
+ const struct tdb_used_record *r;
const void *key;
uint64_t klen, hash;
- r = tdb_get(tdb, off, &pad, sizeof(pad));
+ r = tdb_access_read(tdb, off, sizeof(*r), true);
if (!r)
/* FIXME */
return 0;
klen = rec_key_length(r);
- key = tdb_access_read(tdb, off + sizeof(pad), klen, false);
+ tdb_access_release(tdb, r);
+
+ key = tdb_access_read(tdb, off + sizeof(*r), klen, false);
if (!key)
return 0;
}
/* Get bits from a value. */
-static uint32_t bits(uint64_t val, unsigned start, unsigned num)
+static uint32_t bits_from(uint64_t val, unsigned start, unsigned num)
{
assert(num <= 32);
return (val >> start) & ((1U << num) - 1);
static uint32_t use_bits(struct hash_info *h, unsigned num)
{
h->hash_used += num;
- return bits(h->h, 64 - h->hash_used, num);
+ return bits_from(h->h, 64 - h->hash_used, num);
+}
+
+static bool key_matches(struct tdb_context *tdb,
+ const struct tdb_used_record *rec,
+ tdb_off_t off,
+ const struct tdb_data *key)
+{
+ bool ret = false;
+ const char *rkey;
+
+ if (rec_key_length(rec) != key->dsize) {
+ add_stat(tdb, compare_wrong_keylen, 1);
+ return ret;
+ }
+
+ rkey = tdb_access_read(tdb, off + sizeof(*rec), key->dsize, false);
+ if (!rkey)
+ return ret;
+ if (memcmp(rkey, key->dptr, key->dsize) == 0)
+ ret = true;
+ else
+ add_stat(tdb, compare_wrong_keycmp, 1);
+ tdb_access_release(tdb, rkey);
+ return ret;
}
/* Does entry match? */
tdb_off_t val,
struct tdb_used_record *rec)
{
- bool ret;
- const unsigned char *rkey;
tdb_off_t off;
- /* FIXME: Handle hash value truncated. */
- if (bits(val, TDB_OFF_HASH_TRUNCATED_BIT, 1))
- abort();
-
+ add_stat(tdb, compares, 1);
/* Desired bucket must match. */
- if (h->home_bucket != (val & TDB_OFF_HASH_GROUP_MASK))
+ if (h->home_bucket != (val & TDB_OFF_HASH_GROUP_MASK)) {
+ add_stat(tdb, compare_wrong_bucket, 1);
return false;
+ }
/* Top bits of offset == next bits of hash. */
- if (bits(val, TDB_OFF_HASH_EXTRA_BIT, TDB_OFF_UPPER_STEAL_EXTRA)
- != bits(h->h, 64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
- TDB_OFF_UPPER_STEAL_EXTRA))
+ if (bits_from(val, TDB_OFF_HASH_EXTRA_BIT, TDB_OFF_UPPER_STEAL_EXTRA)
+ != bits_from(h->h, 64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
+ TDB_OFF_UPPER_STEAL_EXTRA)) {
+ add_stat(tdb, compare_wrong_offsetbits, 1);
return false;
+ }
off = val & TDB_OFF_MASK;
if (tdb_read_convert(tdb, off, rec, sizeof(*rec)) == -1)
return false;
- /* FIXME: check extra bits in header? */
- if (rec_key_length(rec) != key->dsize)
+ if ((h->h & ((1 << 11)-1)) != rec_hash(rec)) {
+ add_stat(tdb, compare_wrong_rechash, 1);
return false;
+ }
- rkey = tdb_access_read(tdb, off + sizeof(*rec), key->dsize, false);
- if (!rkey)
- return false;
- ret = (memcmp(rkey, key->dptr, key->dsize) == 0);
- tdb_access_release(tdb, rkey);
- return ret;
+ return key_matches(tdb, rec, off, key);
}
static tdb_off_t hbucket_off(tdb_off_t group_start, unsigned bucket)
+ (bucket % (1 << TDB_HASH_GROUP_BITS)) * sizeof(tdb_off_t);
}
-/* Truncated hashes can't be all 1: that's how we spot a sub-hash */
bool is_subhash(tdb_off_t val)
{
- return val >> (64-TDB_OFF_UPPER_STEAL) == (1<<TDB_OFF_UPPER_STEAL) - 1;
+ return (val >> TDB_OFF_UPPER_STEAL_SUBHASH_BIT) & 1;
+}
+
+/* FIXME: Guess the depth, don't over-lock! */
+static tdb_off_t hlock_range(tdb_off_t group, tdb_off_t *size)
+{
+ *size = 1ULL << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
+ return group << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
+}
+
+static tdb_off_t COLD find_in_chain(struct tdb_context *tdb,
+ struct tdb_data key,
+ tdb_off_t chain,
+ struct hash_info *h,
+ struct tdb_used_record *rec,
+ struct traverse_info *tinfo)
+{
+ tdb_off_t off, next;
+
+ /* In case nothing is free, we set these to zero. */
+ h->home_bucket = h->found_bucket = 0;
+
+ for (off = chain; off; off = next) {
+ unsigned int i;
+
+ h->group_start = off;
+ if (tdb_read_convert(tdb, off, h->group, sizeof(h->group)))
+ return TDB_OFF_ERR;
+
+ for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
+ tdb_off_t recoff;
+ if (!h->group[i]) {
+ /* Remember this empty bucket. */
+ h->home_bucket = h->found_bucket = i;
+ continue;
+ }
+
+ /* We can insert extra bits via add_to_hash
+ * empty bucket logic. */
+ recoff = h->group[i] & TDB_OFF_MASK;
+ if (tdb_read_convert(tdb, recoff, rec, sizeof(*rec)))
+ return TDB_OFF_ERR;
+
+ if (key_matches(tdb, rec, recoff, &key)) {
+ h->home_bucket = h->found_bucket = i;
+
+ if (tinfo) {
+ tinfo->levels[tinfo->num_levels]
+ .hashtable = off;
+ tinfo->levels[tinfo->num_levels]
+ .total_buckets
+ = 1 << TDB_HASH_GROUP_BITS;
+ tinfo->levels[tinfo->num_levels].entry
+ = i;
+ tinfo->num_levels++;
+ }
+ return recoff;
+ }
+ }
+ next = tdb_read_off(tdb, off
+ + offsetof(struct tdb_chain, next));
+ if (next == TDB_OFF_ERR)
+ return TDB_OFF_ERR;
+ if (next)
+ next += sizeof(struct tdb_used_record);
+ }
+ return 0;
}
/* This is the core routine which searches the hashtable for an entry.
group = use_bits(h, TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
- /* FIXME: Guess the depth, don't over-lock! */
- h->hlock_start = (tdb_off_t)group
- << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
- h->hlock_range = 1ULL << (64 - (TDB_TOPLEVEL_HASH_BITS
- - TDB_HASH_GROUP_BITS));
+ h->hlock_start = hlock_range(group, &h->hlock_range);
if (tdb_lock_hashes(tdb, h->hlock_start, h->hlock_range, ltype,
TDB_LOCK_WAIT))
return TDB_OFF_ERR;
tinfo->toplevel_group = group;
tinfo->num_levels = 1;
tinfo->levels[0].entry = 0;
- tinfo->levels[0].hashtable = hashtable
+ tinfo->levels[0].hashtable = hashtable
+ (group << TDB_HASH_GROUP_BITS) * sizeof(tdb_off_t);
tinfo->levels[0].total_buckets = 1 << TDB_HASH_GROUP_BITS;
}
- while (likely(h->hash_used < 64)) {
+ while (h->hash_used <= 64) {
/* Read in the hash group. */
h->group_start = hashtable
+ group * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
return 0;
}
- /* FIXME: We hit the bottom. Chain! */
- abort();
+ return find_in_chain(tdb, key, hashtable, h, rec, tinfo);
fail:
tdb_unlock_hashes(tdb, h->hlock_start, h->hlock_range, ltype);
/* I wrote a simple test, expanding a hash to 2GB, for the following
* cases:
* 1) Expanding all the buckets at once,
- * 2) Expanding the most-populated bucket,
- * 3) Expanding the bucket we wanted to place the new entry ito.
+ * 2) Expanding the bucket we wanted to place the new entry into.
+ * 3) Expanding the most-populated bucket,
*
* I measured the worst/average/best density during this process.
* 1) 3%/16%/30%
{
return h->home_bucket
| new_off
- | ((uint64_t)bits(h->h,
+ | ((uint64_t)bits_from(h->h,
64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
TDB_OFF_UPPER_STEAL_EXTRA)
<< TDB_OFF_HASH_EXTRA_BIT);
}
-/* Simply overwrite the hash entry we found before. */
+/* Simply overwrite the hash entry we found before. */
int replace_in_hash(struct tdb_context *tdb,
struct hash_info *h,
tdb_off_t new_off)
encode_offset(new_off, h));
}
+/* We slot in anywhere that's empty in the chain. */
+static int COLD add_to_chain(struct tdb_context *tdb,
+ tdb_off_t subhash,
+ tdb_off_t new_off)
+{
+ size_t entry = tdb_find_zero_off(tdb, subhash, 1<<TDB_HASH_GROUP_BITS);
+
+ if (entry == 1 << TDB_HASH_GROUP_BITS) {
+ tdb_off_t next;
+
+ next = tdb_read_off(tdb, subhash
+ + offsetof(struct tdb_chain, next));
+ if (next == TDB_OFF_ERR)
+ return -1;
+
+ if (!next) {
+ next = alloc(tdb, 0, sizeof(struct tdb_chain), 0,
+ TDB_CHAIN_MAGIC, false);
+ if (next == TDB_OFF_ERR)
+ return -1;
+ if (zero_out(tdb, next+sizeof(struct tdb_used_record),
+ sizeof(struct tdb_chain)))
+ return -1;
+ if (tdb_write_off(tdb, subhash
+ + offsetof(struct tdb_chain, next),
+ next) != 0)
+ return -1;
+ }
+ return add_to_chain(tdb, next, new_off);
+ }
+
+ return tdb_write_off(tdb, subhash + entry * sizeof(tdb_off_t),
+ new_off);
+}
+
/* Add into a newly created subhash. */
static int add_to_subhash(struct tdb_context *tdb, tdb_off_t subhash,
unsigned hash_used, tdb_off_t val)
h.hash_used = hash_used;
- /* FIXME chain if hash_used == 64 */
if (hash_used + TDB_SUBLEVEL_HASH_BITS > 64)
- abort();
+ return add_to_chain(tdb, subhash, off);
- /* FIXME: Do truncated hash bits if we can! */
h.h = hash_record(tdb, off);
gnum = use_bits(&h, TDB_SUBLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS);
- h.group_start = subhash + sizeof(struct tdb_used_record)
+ h.group_start = subhash
+ gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
h.home_bucket = use_bits(&h, TDB_HASH_GROUP_BITS);
static int expand_group(struct tdb_context *tdb, struct hash_info *h)
{
- unsigned bucket, num_vals, i;
+ unsigned bucket, num_vals, i, magic;
+ size_t subsize;
tdb_off_t subhash;
tdb_off_t vals[1 << TDB_HASH_GROUP_BITS];
/* Attach new empty subhash under fullest bucket. */
bucket = fullest_bucket(tdb, h->group, h->home_bucket);
- subhash = alloc(tdb, 0, sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS,
- 0, false);
+ if (h->hash_used == 64) {
+ add_stat(tdb, alloc_chain, 1);
+ subsize = sizeof(struct tdb_chain);
+ magic = TDB_CHAIN_MAGIC;
+ } else {
+ add_stat(tdb, alloc_subhash, 1);
+ subsize = (sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS);
+ magic = TDB_HTABLE_MAGIC;
+ }
+
+ subhash = alloc(tdb, 0, subsize, 0, magic, false);
if (subhash == TDB_OFF_ERR)
return -1;
- if (zero_out(tdb, subhash + sizeof(struct tdb_used_record),
- sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS) == -1)
+ if (zero_out(tdb, subhash + sizeof(struct tdb_used_record), subsize))
return -1;
/* Remove any which are destined for bucket or are in wrong place. */
/* assert(num_vals); */
/* Overwrite expanded bucket with subhash pointer. */
- h->group[bucket] = subhash | ~((1ULL << (64 - TDB_OFF_UPPER_STEAL))-1);
+ h->group[bucket] = subhash | (1ULL << TDB_OFF_UPPER_STEAL_SUBHASH_BIT);
+
+ /* Point to actual contents of record. */
+ subhash += sizeof(struct tdb_used_record);
/* Put values back. */
for (i = 0; i < num_vals; i++) {
int add_to_hash(struct tdb_context *tdb, struct hash_info *h, tdb_off_t new_off)
{
- /* FIXME: chain! */
- if (h->hash_used >= 64)
- abort();
-
/* We hit an empty bucket during search? That's where it goes. */
if (!h->group[h->found_bucket]) {
h->group[h->found_bucket] = encode_offset(new_off, h);
h->group, sizeof(h->group));
}
+ if (h->hash_used > 64)
+ return add_to_chain(tdb, h->group_start, new_off);
+
/* We're full. Expand. */
if (expand_group(tdb, h) == -1)
return -1;
tlevel++;
tlevel->hashtable = off + sizeof(struct tdb_used_record);
tlevel->entry = 0;
- tlevel->total_buckets = (1 << TDB_SUBLEVEL_HASH_BITS);
+ /* Next level is a chain? */
+ if (unlikely(tinfo->num_levels == TDB_MAX_LEVELS + 1))
+ tlevel->total_buckets = (1 << TDB_HASH_GROUP_BITS);
+ else
+ tlevel->total_buckets = (1 << TDB_SUBLEVEL_HASH_BITS);
goto again;
}
if (tinfo->num_levels == 1)
return 0;
+ /* Handle chained entries. */
+ if (unlikely(tinfo->num_levels == TDB_MAX_LEVELS + 1)) {
+ tlevel->hashtable = tdb_read_off(tdb, tlevel->hashtable
+ + offsetof(struct tdb_chain,
+ next));
+ if (tlevel->hashtable == TDB_OFF_ERR)
+ return TDB_OFF_ERR;
+ if (tlevel->hashtable) {
+ tlevel->hashtable += sizeof(struct tdb_used_record);
+ tlevel->entry = 0;
+ goto again;
+ }
+ }
+
/* Go back up and keep searching. */
tinfo->num_levels--;
tlevel--;
/* Return 1 if we find something, 0 if not, -1 on error. */
int next_in_hash(struct tdb_context *tdb, int ltype,
struct traverse_info *tinfo,
- TDB_DATA *kbuf, unsigned int *dlen)
+ TDB_DATA *kbuf, size_t *dlen)
{
const unsigned group_bits = TDB_TOPLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS;
- tdb_off_t hlock_start, hlock_range, off;
+ tdb_off_t hl_start, hl_range, off;
while (tinfo->toplevel_group < (1 << group_bits)) {
- hlock_start = (tdb_off_t)tinfo->toplevel_group
+ hl_start = (tdb_off_t)tinfo->toplevel_group
<< (64 - group_bits);
- hlock_range = 1ULL << group_bits;
- if (tdb_lock_hashes(tdb, hlock_start, hlock_range, ltype,
+ hl_range = 1ULL << group_bits;
+ if (tdb_lock_hashes(tdb, hl_start, hl_range, ltype,
TDB_LOCK_WAIT) != 0)
return -1;
if (tdb_read_convert(tdb, off, &rec, sizeof(rec))) {
tdb_unlock_hashes(tdb,
- hlock_start, hlock_range,
- ltype);
+ hl_start, hl_range, ltype);
return -1;
}
+ if (rec_magic(&rec) != TDB_USED_MAGIC) {
+ tdb_logerr(tdb, TDB_ERR_CORRUPT,
+ TDB_LOG_ERROR,
+ "next_in_hash:"
+ " corrupt record at %llu",
+ (long long)off);
+ return -1;
+ }
+
kbuf->dsize = rec_key_length(&rec);
/* They want data as well? */
if (dlen) {
*dlen = rec_data_length(&rec);
- kbuf->dptr = tdb_alloc_read(tdb,
+ kbuf->dptr = tdb_alloc_read(tdb,
off + sizeof(rec),
kbuf->dsize
+ *dlen);
} else {
- kbuf->dptr = tdb_alloc_read(tdb,
+ kbuf->dptr = tdb_alloc_read(tdb,
off + sizeof(rec),
kbuf->dsize);
}
- tdb_unlock_hashes(tdb, hlock_start, hlock_range, ltype);
+ tdb_unlock_hashes(tdb, hl_start, hl_range, ltype);
return kbuf->dptr ? 1 : -1;
}
- tdb_unlock_hashes(tdb, hlock_start, hlock_range, ltype);
+ tdb_unlock_hashes(tdb, hl_start, hl_range, ltype);
tinfo->toplevel_group++;
tinfo->levels[0].hashtable
/* Return 1 if we find something, 0 if not, -1 on error. */
int first_in_hash(struct tdb_context *tdb, int ltype,
struct traverse_info *tinfo,
- TDB_DATA *kbuf, unsigned int *dlen)
+ TDB_DATA *kbuf, size_t *dlen)
{
tinfo->prev = 0;
tinfo->toplevel_group = 0;
return next_in_hash(tdb, ltype, tinfo, kbuf, dlen);
}
-TDB_DATA tdb_firstkey(struct tdb_context *tdb)
+/* Even if the entry isn't in this hash bucket, you'd have to lock this
+ * bucket to find it. */
+static int chainlock(struct tdb_context *tdb, const TDB_DATA *key,
+ int ltype, enum tdb_lock_flags waitflag,
+ const char *func)
{
- struct traverse_info tinfo;
- struct tdb_data k;
- switch (first_in_hash(tdb, F_RDLCK, &tinfo, &k, NULL)) {
- case 1:
- return k;
- case 0:
- tdb->ecode = TDB_SUCCESS;
- /* Fall thru... */
- default:
- return tdb_null;
- }
-}
+ int ret;
+ uint64_t h = tdb_hash(tdb, key->dptr, key->dsize);
+ tdb_off_t lockstart, locksize;
+ unsigned int group, gbits;
+
+ gbits = TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS;
+ group = bits_from(h, 64 - gbits, gbits);
+
+ lockstart = hlock_range(group, &locksize);
-/* We lock twice, not very efficient. We could keep last key & tinfo cached. */
-TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA key)
+ ret = tdb_lock_hashes(tdb, lockstart, locksize, ltype, waitflag);
+ tdb_trace_1rec(tdb, func, *key);
+ return ret;
+}
+
+/* lock/unlock one hash chain. This is meant to be used to reduce
+ contention - it cannot guarantee how many records will be locked */
+int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
{
- struct traverse_info tinfo;
- struct hash_info h;
- struct tdb_used_record rec;
-
- tinfo.prev = find_and_lock(tdb, key, F_RDLCK, &h, &rec, &tinfo);
- if (unlikely(tinfo.prev == TDB_OFF_ERR))
- return tdb_null;
- tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_RDLCK);
-
- switch (next_in_hash(tdb, F_RDLCK, &tinfo, &key, NULL)) {
- case 1:
- return key;
- case 0:
- tdb->ecode = TDB_SUCCESS;
- /* Fall thru... */
- default:
- return tdb_null;
- }
-}
+ return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_WAIT, "tdb_chainlock");
+}
+
+int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
+{
+ uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
+ tdb_off_t lockstart, locksize;
+ unsigned int group, gbits;
+
+ gbits = TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS;
+ group = bits_from(h, 64 - gbits, gbits);
+
+ lockstart = hlock_range(group, &locksize);
+
+ tdb_trace_1rec(tdb, "tdb_chainunlock", key);
+ return tdb_unlock_hashes(tdb, lockstart, locksize, F_WRLCK);
+}
projects / ccan / blobdiff