[FLINK-934] Remove default values for JVM heap sizes in startup scripts

[uce]

This is a fix for FLINK-934. As a follow up we should have the heap config keys only as suggested entries (commented out) in FLINK-898 aka #6.

With jobmanager.heap.mb and taskmanager.heap.mb not set, 16 GB of main memory and Java 7.

$ ./bin/start-local.sh 
Starting job manager
$ jps
9601 JobManager
$ jinfo -flag MaxHeapSize 9601
-XX:MaxHeapSize=4294967296

JobManager with 4294967296/2^20 = 4096 MB heap size.

---

$ bin/start-cluster.sh 
Starting job manager
Starting task manager on host batman
$ jps
10049 TaskManager
9966 JobManager
$ jinfo -flag MaxHeapSize 9966
-XX:MaxHeapSize=4294967296
$jinfo -flag MaxHeapSize 10049
-XX:MaxHeapSize=4294967296

Both JobManager and TaskManager with 4294967296/2^20 = 4096 MB heap size each.

---

Setting jobmanager.heap.mb and taskmanager.heap.mb to 256 and 512 MB respectively.

$ bin/start-local.sh 
Starting job manager
$ jps
10542 JobManager
$ jinfo -flag MaxHeapSize 10542
-XX:MaxHeapSize=805306368

JobManager with 805306368/2^20 = 768 MB (256 for the JobManager and 512 MB for the TaskManager).

---

$ bin/start-cluster.sh 
Starting job manager
Starting task manager on host batman
$ jps
10833 JobManager
10918 TaskManager
$ jinfo -flag MaxHeapSize 10833
-XX:MaxHeapSize=268435456
$jinfo -flag MaxHeapSize 10918
-XX:MaxHeapSize=536870912

JobManager with 268435456/2^20 = 256 MB and TaskManager with 536870912/2^20 = 512 MB.

[asfbot]

Robert Metzger on dev@flink.incubator.apache.org replies:
Testing Github <--> ML integration.

[StephanEwen]

Okay, that looks good. The other flags (max perm gen size, mark sweep GC, mark sweep class unloading) are unaffected by that?

[StephanEwen]

When we pass the flags, we make sure that Xms and -Xmx are the same, to prevent the JVM from being funny and resizing the heap from time to time. I think we loose that with this option. But I guess its all right, on cluster setups we would expect those to be set anyways.

[uce]

Yes, the other flags are set as before. The Xms and Xmx flags are only set, when they are found in stratosphere-conf.yaml.

While doing the PR, I came to the same conclusion as your second comment. But we can actually also do something more fancy and figure out the available memory ourselves and set it (thereby circumventing the defaults).

[StephanEwen]

Let's not do this ourselves. I think it is fine. If you want a robust setup, set the values. Our YARN scripts also set them automatically, based on the container size, afaik.

[StephanEwen]

I will merge this...