e18db9e984
Each thread now keeps the last ~512 kB of freed objects into a local cache. There are some heuristics involved so that a specific pool cannot use more than 1/8 of the total cache in number of objects. Tests have shown that 512 kB is an optimal size on a 24-thread test running on a dual-socket machine, resulting in an overall 7.5% performance increase and a cache miss ratio reducing from 19.2 to 17.7%. Anyway it seems pointless to keep more than an L2 cache, which probably explains why sizes between 256 and 512 kB are optimal. Cached objects appear in two lists, one per pool and one LRU to help with fair eviction. Currently there is no way to check each thread's cache state nor to flush it. This cache cannot be disabled and is enabled as soon as the lockless pools are enabled (i.e.: threads are enabled, no pool debugging is in use and the CPU supports a double word CAS).