The first HeapLRU evictions on large region can consume high amounts of CPU

If you have a region configured for HeapLRU eviction and are able to put a large number of entries in it before hitting the eviction threshold, then the first evictions will consume much more CPU than subsequent evictions. The reason for this is that the eviction list is not initialized until the first eviction is done. At that time a scan is done of all the existing entries marking each one as not having been recently used. This can touch a large number of memory pages and also hits some common synchronization locks. You can see that this is happening by looking at the HeapLRUStats.lruEvaluations stat.