Parallel eviction

Eviction changes allowing to evict (remap) cachelines while
holding hash bucket write lock instead of global metadata
write lock.

As eviction (replacement) is now tightly coupled with request,
each request uses eviction size equal to number of its
unmapped cachelines.

Evicting without global metadata write lock is possible
thanks to the fact that remaping is always performed
while exclusively holding cacheline (read or write) lock.
So for a cacheline on LRU list we acquire cacheline lock,
safely resolve hash and consequently write-lock hash bucket.
Since cacheline lock is acquired under hash bucket (everywhere
except for new eviction implementation), we are certain that
noone acquires cacheline lock behind our back. Concurrent
eviction threads are eliminated by holding eviction list
lock for the duration of critial locking operations.

Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>

src/ocf_queue_priv.h

@@ -21,6 +21,9 @@ struct ocf_queue {
 	/* per-queue free running global metadata lock index */
 	unsigned lock_idx;
 
+	/* per-queue free running eviction list index */
+	unsigned eviction_idx;
+
 	/* Tracing reference counter */
 	env_atomic64 trace_ref_cntr;