Gabor Gevay created FLINK-3322: ---------------------------------- Summary: MemoryManager creates too much GC pressure with iterative jobs Key: FLINK-3322 URL: https://issues.apache.org/jira/browse/FLINK-3322 Project: Flink Issue Type: Bug Components: Distributed Runtime Affects Versions: 1.0.0 Reporter: Gabor Gevay
When taskmanager.memory.preallocate is false (the default), released memory segments are not added to a pool, but the GC is expected to take care of them. This puts too much pressure on the GC with iterative jobs, where the operators reallocate all memory at every superstep. See the following discussion on the mailing list: http://apache-flink-mailing-list-archive.1008284.n3.nabble.com/Memory-manager-behavior-in-iterative-jobs-tt10066.html Reproducing the issue: https://github.com/ggevay/flink/tree/MemoryManager-crazy-gc The class to start is malom.Solver. If you increase the memory given to the JVM from 1 to 50 GB, performance gradually degrades by more than 10 times. (It will generate some lookuptables to /tmp on first run for a few minutes.) (I think the slowdown might also depend somewhat on taskmanager.memory.fraction, because more unused non-managed memory results in rarer GCs.) -- This message was sent by Atlassian JIRA (v6.3.4#6332)