selinux: reduce the use of hard-coded hash sizes

Instead allocate hash tables with just the right size based on the
actual number of elements (which is almost always known beforehand, we
just need to defer the hashtab allocation to the right time). The only
case when we don't know the size (with the current policy format) is the
new filename transitions hashtable. Here I just left the existing value.

After this patch, the time to load Fedora policy on x86_64 decreases
from 790 ms to 167 ms. If the unconfined module is removed, it decreases
from 750 ms to 122 ms. It is also likely that other operations are going
to be faster, mainly string_to_context_struct() or mls_compute_sid(),
but I didn't try to quantify that.

The memory usage of all hash table arrays increases from ~58 KB to
~163 KB (with Fedora policy on x86_64).

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/security/selinux/ss/hashtab.h b/security/selinux/ss/hashtab.h
index 3e3e42bfd150..dde54d9ff01c 100644
--- a/security/selinux/ss/hashtab.h
+++ b/security/selinux/ss/hashtab.h
@@ -42,7 +42,7 @@ struct hashtab_info {
  */
 struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h, const void *key),
 			       int (*keycmp)(struct hashtab *h, const void *key1, const void *key2),
-			       u32 size);
+			       u32 nel_hint);
 
 /*
  * Inserts the specified (key, datum) pair into the specified hash table.