On Thursday 12 February 2009 02:50:43 pm Eric Paris wrote:
> Currently SELinux code has an atomic which was intended to track how many
> times an avc entry was used and to evict entries when they haven't been
> used recently. Instead we never let this atomic get above 1 and evict when
> it is first checked for eviction since it hits zero. This is a total waste
> of time so I'm completely dropping ae.used.
>
> This change resulted in about a 3% faster avc_has_perm_noaudit when running
> oprofile against a tbench benchmark.
>
> Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
Looks okay to me, I did notice another optimization (see below) that might be
worth including if you respin the patch.
Reviewed by: Paul Moore <paul.moore@xxxxxx>
> struct avc_node {
> @@ -321,16 +320,13 @@ static inline int avc_reclaim_node(void)
>
> rcu_read_lock();
> list_for_each_entry(node, &avc_cache.slots[hvalue], list) {
> - if (atomic_dec_and_test(&node->ae.used)) {
> - /* Recently Unused */
> - avc_node_delete(node);
> - avc_cache_stats_incr(reclaims);
> - ecx++;
> - if (ecx >= AVC_CACHE_RECLAIM) {
> - rcu_read_unlock();
> - spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
> - goto out;
> - }
> + avc_node_delete(node);
> + avc_cache_stats_incr(reclaims);
> + ecx++;
> + if (ecx >= AVC_CACHE_RECLAIM) {
> + rcu_read_unlock();
> + spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
> + goto out;
> }
> }
> rcu_read_unlock();
Not your fault, but in reviewing this code I realized we aren't really using
the avc_cache.lru_hint atomic either; it looks like it is initialized to zero
and never changes. With that in mind we could remove the lru_hint field from
the avc_cache and simplify the above function a tiny bit (no need for hvalue,
just use zero).
--
paul moore
linux @ hp
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