Hi @antirez

There are three problems about lazyfree eviction I think:

1. We forgot the latency generated by waiting for BIO_LAZY_FREE

   I think it's necessary to record this kind of latency.

2. Maybe we misuse latencyRemoveNestedEvent

   In my opinion the eviction-cycle should contains all latency, including eviction-del and eviction-lazyfree, so we should not remove eviction-del from eviction-cycle.

3. The last problem is about cant_free

   When we goto cant_free, we wait for BIO_LAZY_FREE finished or break if already freed enough memory.

   But, we use mem_freed duplicately.

       while(bioPendingJobsOfType(BIO_LAZY_FREE)) {
           if (((mem_reported - zmalloc_used_memory()) + mem_freed) >= mem_tofree)
               break;
           usleep(1000);
       }
   

   I add a variable mem_used_init to record the initial used memory, please check.