Gabor Gevay created FLINK-3322:
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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.)
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