pack: evict all of the pages at once

Somewhat surprisingly, this can increase the speed considerably, as we
don't bother trying to decide what to evict, and the most used entries
are quickly back into the cache.

src/pack.c

@@ -116,49 +116,22 @@ static git_pack_cache_entry *cache_get(git_pack_cache *cache, git_off_t offset)
 	return entry;
 }
 
-#define BASE_DELTA_EVICT_NR 8
-
 /* Run with the cache lock held */
 static void free_lowest_entry(git_pack_cache *cache)
 {
 	git_pack_cache_entry *entry;
 	khiter_t k;
 
-	git_pack_cache_entry *lru[BASE_DELTA_EVICT_NR] = {NULL};
-	khiter_t lru_k[BASE_DELTA_EVICT_NR];
-	int i;
-
 	for (k = kh_begin(cache->entries); k != kh_end(cache->entries); k++) {
 		if (!kh_exist(cache->entries, k))
 			continue;
 
 		entry = kh_value(cache->entries, k);
 
-		for (i = 0; i < BASE_DELTA_EVICT_NR; i++) {
-			if (lru[i] == NULL ||
-			    (entry->last_usage < lru[i]->last_usage &&
-			     entry->refcount.val == 0)) {
-				int j;
-
-				for (j = 0; j < i; j++) {
-					lru[j] = lru[j+1];
-					lru_k[j] = lru_k[j+1];
-				}
-
-				lru[i] = entry;
-				lru_k[i] = k;
-
-				/* jump out and try with the next entry */
-				break;
-			}
-		}
-	}
-
-	for (i = 0; i < BASE_DELTA_EVICT_NR; i++) {
-		if (lru[i]) {
-			cache->memory_used -= lru[i]->raw.len;
-			kh_del(off, cache->entries, lru_k[i]);
-			free_cache_object(lru[i]);
+		if (entry && entry->refcount.val == 0) {
+			cache->memory_used -= entry->raw.len;
+			kh_del(off, cache->entries, k);
+			free_cache_object(entry);
 		}
 	}
 }