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Help to Understand cutoff memory

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Lu Niu

Help to Understand cutoff memory

Hi, flink users

I have some question regarding memory allocation. According to doc, containerized.heap-cutoff-ratio means:

```

Percentage of heap space to remove from containers (YARN / Mesos), to compensate for other JVM memory usage

```

However, I find cutoff memory is actually treated as "part of direct memory":

https://github.com/apache/flink/blob/release-1.9.1/flink-runtime/src/test/java/org/apache/flink/runtime/clusterframework/ContaineredTaskManagerParametersTest.java#L67

The code above shows the max of MaxDirectMemorySize of jvm process is the sum of networkbuffer + cutoff. Then, there is no guarantee of a fixed headroom in container memory. In our case we use rocksDB memory and we found many times DirectMemory is close to maximum, leaving less headroom in the container for rocksdb. Could someone help on this? thanks

Best

Theo

Re: Help to Understand cutoff memory

Hi Lu,

I found this talk on last Flink Forward in Berlin very helpful in order to understand JVM RAM and cutoff memory [1]. Maybe it helps you understand that stuff better.

In my experiences on YARN, the author was totally correct. I was able to reproduce that by assigning something about 12GB for taskmanager memory, setting cutoff to 0.15 and let network stay on 0.1 , I got something round about 8-9GB RAM for my real taskmanager JVM memory.

Best regards