From d615e534e870a911f11b7b88021242220ea053bf Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Tue, 2 Apr 2019 10:19:19 +1030 Subject: [PATCH 1/1] htable: reduce size of htable by storing perfect bitnum, not mask. Signed-off-by: Rusty Russell --- ccan/htable/htable.c | 34 ++++++++++++++++++++++------------ ccan/htable/htable.h | 5 ++--- ccan/htable/test/run-debug.c | 8 ++++---- ccan/htable/test/run.c | 8 ++++---- ccan/htable/tools/speed.c | 4 ++-- 5 files changed, 34 insertions(+), 25 deletions(-) diff --git a/ccan/htable/htable.c b/ccan/htable/htable.c index 2028d336..b27d063f 100644 --- a/ccan/htable/htable.c +++ b/ccan/htable/htable.c @@ -58,6 +58,15 @@ static inline bool entry_is_valid(uintptr_t e) return e > HTABLE_DELETED; } +/* We use 0 to mean we don't have a perfect bit, otherwise it's + * bit n - 1 */ +static inline uintptr_t ht_perfect_mask(const struct htable *ht) +{ + if (ht->perfect_bitnum > 0) + return (uintptr_t)1 << (ht->perfect_bitnum - 1); + return 0; +} + static inline uintptr_t get_hash_ptr_bits(const struct htable *ht, size_t hash) { @@ -65,7 +74,7 @@ static inline uintptr_t get_hash_ptr_bits(const struct htable *ht, * end is quite expensive. But the lower bits are redundant, so * we fold the value first. */ return (hash ^ (hash >> ht->bits)) - & ht->common_mask & ~ht->perfect_bit; + & ht->common_mask & ~ht_perfect_mask(ht); } void htable_init(struct htable *ht, @@ -75,7 +84,7 @@ void htable_init(struct htable *ht, *ht = empty; ht->rehash = rehash; ht->priv = priv; - ht->table = &ht->perfect_bit; + ht->table = &ht->common_bits; } static inline size_t ht_max(const struct htable *ht) @@ -102,7 +111,7 @@ bool htable_init_sized(struct htable *ht, ht->table = htable_alloc(ht, sizeof(size_t) << ht->bits); if (!ht->table) { - ht->table = &ht->perfect_bit; + ht->table = &ht->common_bits; return false; } (void)htable_debug(ht, HTABLE_LOC); @@ -111,7 +120,7 @@ bool htable_init_sized(struct htable *ht, void htable_clear(struct htable *ht) { - if (ht->table != &ht->perfect_bit) + if (ht->table != &ht->common_bits) htable_free(ht, (void *)ht->table); htable_init(ht, ht->rehash, ht->priv); } @@ -154,7 +163,7 @@ void *htable_firstval_(const struct htable *ht, struct htable_iter *i, size_t hash) { i->off = hash_bucket(ht, hash); - return htable_val(ht, i, hash, ht->perfect_bit); + return htable_val(ht, i, hash, ht_perfect_mask(ht)); } void *htable_nextval_(const struct htable *ht, @@ -197,7 +206,7 @@ void *htable_prev_(const struct htable *ht, struct htable_iter *i) static void ht_add(struct htable *ht, const void *new, size_t h) { size_t i; - uintptr_t perfect = ht->perfect_bit; + uintptr_t perfect = ht_perfect_mask(ht); i = hash_bucket(ht, h); @@ -223,16 +232,16 @@ static COLD bool double_table(struct htable *ht) ht->bits++; /* If we lost our "perfect bit", get it back now. */ - if (!ht->perfect_bit && ht->common_mask) { + if (ht->perfect_bitnum == 0 && ht->common_mask) { for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) { if (ht->common_mask & ((size_t)1 << i)) { - ht->perfect_bit = (size_t)1 << i; + ht->perfect_bitnum = i + 1; break; } } } - if (oldtable != &ht->perfect_bit) { + if (oldtable != &ht->common_bits) { for (i = 0; i < oldnum; i++) { if (entry_is_valid(e = oldtable[i])) { void *p = get_raw_ptr(ht, e); @@ -262,7 +271,7 @@ static COLD void rehash_table(struct htable *ht) continue; if (e == HTABLE_DELETED) ht->table[h] = 0; - else if (!(e & ht->perfect_bit)) { + else if (!(e & ht_perfect_mask(ht))) { void *p = get_raw_ptr(ht, e); ht->table[h] = 0; ht_add(ht, p, ht->rehash(p, ht->priv)); @@ -290,7 +299,7 @@ static COLD void update_common(struct htable *ht, const void *p) ht->common_mask = ~((uintptr_t)1 << i); ht->common_bits = ((uintptr_t)p & ht->common_mask); - ht->perfect_bit = 1; + ht->perfect_bitnum = 1; (void)htable_debug(ht, HTABLE_LOC); return; } @@ -313,7 +322,8 @@ static COLD void update_common(struct htable *ht, const void *p) /* Take away those bits from our mask, bits and perfect bit. */ ht->common_mask &= ~maskdiff; ht->common_bits &= ~maskdiff; - ht->perfect_bit &= ~maskdiff; + if (ht_perfect_mask(ht) & maskdiff) + ht->perfect_bitnum = 0; (void)htable_debug(ht, HTABLE_LOC); } diff --git a/ccan/htable/htable.h b/ccan/htable/htable.h index bdce920b..938b43af 100644 --- a/ccan/htable/htable.h +++ b/ccan/htable/htable.h @@ -24,11 +24,10 @@ struct htable { size_t (*rehash)(const void *elem, void *priv); void *priv; - unsigned int bits; + unsigned int bits, perfect_bitnum; size_t elems, deleted; /* These are the bits which are the same in all pointers. */ uintptr_t common_mask, common_bits; - uintptr_t perfect_bit; uintptr_t *table; }; @@ -50,7 +49,7 @@ struct htable { * static struct htable ht = HTABLE_INITIALIZER(ht, rehash, NULL); */ #define HTABLE_INITIALIZER(name, rehash, priv) \ - { rehash, priv, 0, 0, 0, -1, 0, 0, &name.perfect_bit } + { rehash, priv, 0, 0, 0, 0, -1, 0, &name.common_bits } /** * htable_init - initialize an empty hash table. diff --git a/ccan/htable/test/run-debug.c b/ccan/htable/test/run-debug.c index ce4c4103..b9f48ee7 100644 --- a/ccan/htable/test/run-debug.c +++ b/ccan/htable/test/run-debug.c @@ -194,17 +194,17 @@ int main(void) /* Corner cases: wipe out the perfect bit using bogus pointer. */ htable_clear(&ht); htable_add(&ht, hash(&val[NUM_VALS-1], NULL), &val[NUM_VALS-1]); - ok1(ht.perfect_bit); - perfect_bit = ht.perfect_bit; + ok1(ht_perfect_mask(&ht)); + perfect_bit = ht_perfect_mask(&ht); bad_pointer = (void *)((uintptr_t)&val[NUM_VALS-1] | perfect_bit); htable_add(&ht, 0, bad_pointer); - ok1(ht.perfect_bit == 0); + ok1(ht_perfect_mask(&ht) == 0); htable_del(&ht, 0, bad_pointer); /* Enlarging should restore it... */ add_vals(&ht, val, 0, NUM_VALS-1); - ok1(ht.perfect_bit != 0); + ok1(ht_perfect_mask(&ht) != 0); htable_clear(&ht); ok1(htable_init_sized(&ht, hash, NULL, 1024)); diff --git a/ccan/htable/test/run.c b/ccan/htable/test/run.c index 067816a9..85502c4a 100644 --- a/ccan/htable/test/run.c +++ b/ccan/htable/test/run.c @@ -183,17 +183,17 @@ int main(void) /* Corner cases: wipe out the perfect bit using bogus pointer. */ htable_clear(&ht); htable_add(&ht, 0, (void *)((uintptr_t)&val[NUM_VALS-1])); - ok1(ht.perfect_bit); - perfect_bit = ht.perfect_bit; + ok1(ht_perfect_mask(&ht)); + perfect_bit = ht_perfect_mask(&ht); htable_add(&ht, 0, (void *)((uintptr_t)&val[NUM_VALS-1] | perfect_bit)); - ok1(ht.perfect_bit == 0); + ok1(ht_perfect_mask(&ht) == 0); htable_del(&ht, 0, (void *)((uintptr_t)&val[NUM_VALS-1] | perfect_bit)); /* Enlarging should restore it... */ add_vals(&ht, val, 0, NUM_VALS-1); - ok1(ht.perfect_bit != 0); + ok1(ht_perfect_mask(&ht) != 0); htable_clear(&ht); ok1(htable_init_sized(&ht, hash, NULL, 1024)); diff --git a/ccan/htable/tools/speed.c b/ccan/htable/tools/speed.c index dce3fdf9..e185b6f6 100644 --- a/ccan/htable/tools/speed.c +++ b/ccan/htable/tools/speed.c @@ -74,8 +74,8 @@ static size_t perfect(const struct htable *ht) continue; if (hash_bucket(ht, ht->rehash(get_raw_ptr(ht, ht->table[i]), ht->priv)) == i) { - assert((ht->table[i] & ht->perfect_bit) - == ht->perfect_bit); + assert((ht->table[i] & ht_perfect_mask(ht)) + == ht_perfect_mask(ht)); placed_perfect++; } } -- 2.39.2