Now every cache has own TTL manager, which creates CleanupWorker = new extra thread. This can cause to extra hundreds of threads (redundant context switches = performance penalty).
Also, under IGNITE-3513 <https://issues.apache.org/jira/browse/IGNITE-3513> every put can enter critical section to notify worker. Obviously, it is not good from performance point of view. So, my proposal is next: 1. Expiration should be done on every cache action (on exit thread which updates cache should invoke expire). 2. TtlManager will exist only in one instance. 3. CleanupWorker will be the only backup if there is no cache activity. It will wake up with some period to check for work (500 ms, for example). Moreover, now we keep on-heap pending entries even if a cache is kept off-head. At least, this issue needs discussion.
