[MAPREDUCE-5785] Derive heap size or mapreduce.*.memory.mb automatically

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha1
• Component/s: mr-am, task
• Hadoop Flags: Incompatible change

Release Note

The memory values for mapreduce.map/reduce.memory.mb keys, if left to their default values of -1, will now be automatically inferred from the heap size value system property (-Xmx) specified for mapreduce.map/reduce.java.opts keys.

The converse is also done, i.e. if mapreduce.map/reduce.memory.mb values are specified, but no -Xmx is supplied for mapreduce.map/reduce.java.opts keys, then the -Xmx value will be derived from the former's value.

If neither is specified, then a default value of 1024 MB gets used.

For both these conversions, a scaling factor specified by property mapreduce.job.heap.memory-mb.ratio is used, to account for overheads between heap usage vs. actual physical memory usage.

Existing configs or job code that already specify both the set of properties explicitly would not be affected by this inferring change.

• Assignee: Gera Shegalov
• Reporter: Gera Shegalov
• Created: 08/Mar/14 12:44
• Updated: 27/Jun/19 08:54
• Resolved: 22/Jan/15 02:57

Description

Currently users have to set 2 memory-related configs per Job / per task type. One first chooses some container size map reduce.*.memory.mb and then a corresponding maximum Java heap size Xmx < map reduce.*.memory.mb. This makes sure that the JVM's C-heap (native memory + Java heap) does not exceed this mapreduce.*.memory.mb. If one forgets to tune Xmx, MR-AM might be

• allocating big containers whereas the JVM will only use the default -Xmx200m.
• allocating small containers that will OOM because Xmx is too high.

With this JIRA, we propose to set Xmx automatically based on an empirical ratio that can be adjusted. Xmx is not changed automatically if provided by the user.

Issue Links

• breaks: MAPREDUCE-6223 TestJobConf#testNegativeValueForTaskVmem failures
• breaks: MAPREDUCE-6234 TestHighRamJob fails due to the change in MAPREDUCE-5785
• causes: HIVE-21929 Hive on Tez requers explicite set of property hive.tez.container.size
• is related to: MAPREDUCE-5892 Derive MR-AM container size and Xmx based on the job size: number of splits and reduces
• relates to: TEZ-699 Have sensible defaults for java opts
• relates to: MAPREDUCE-6343 JobConf.parseMaximumHeapSizeMB() fails to parse value greater than 2GB expressed in bytes