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libsepol: grow hashtab dynamically

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Detect when the hashtab's load factor gets too high and try to grow it
and rehash it in such case. If the reallocation fails, just keep the
hashtab at its current size, since this is not a fatal error (it will
just be slower).

This speeds up semodule -BN on Fedora from ~8.9s to ~7.2s (1.7 seconds
saved).

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
This commit is contained in:
Ondrej Mosnacek 2020-02-19 16:43:42 +01:00 committed by Stephen Smalley
parent 00bdfefcce
commit ee4b20ca10
1 changed files with 41 additions and 0 deletions
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41
libsepol/src/hashtab.c
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@ -63,6 +63,45 @@ hashtab_t hashtab_create(unsigned int (*hash_value) (hashtab_t h,
return p;
}
static void hashtab_check_resize(hashtab_t h)
{
unsigned int hvalue, i, old_size, new_size = h->size;
hashtab_ptr_t *new_htable, *dst, cur, next;
while (new_size <= h->nel && new_size * 2 != 0)
new_size *= 2;
if (h->size == new_size)
return;
new_htable = calloc(new_size, sizeof(*new_htable));
if (!new_htable)
return;
old_size = h->size;
h->size = new_size;
/* Move all elements to the new htable */
for (i = 0; i < old_size; i++) {
cur = h->htable[i];
while (cur != NULL) {
hvalue = h->hash_value(h, cur->key);
dst = &new_htable[hvalue];
while (*dst && h->keycmp(h, cur->key, (*dst)->key) > 0)
dst = &(*dst)->next;
next = cur->next;
cur->next = *dst;
*dst = cur;
cur = next;
}
}
free(h->htable);
h->htable = new_htable;
}
int hashtab_insert(hashtab_t h, hashtab_key_t key, hashtab_datum_t datum)
{
int hvalue;
@ -71,6 +110,8 @@ int hashtab_insert(hashtab_t h, hashtab_key_t key, hashtab_datum_t datum)
if (!h)
return SEPOL_ENOMEM;
hashtab_check_resize(h);
hvalue = h->hash_value(h, key);
prev = NULL;
cur = h->htable[hvalue];