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https://issues.apache.org/jira/browse/MAPREDUCE-5785?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Harsh J updated MAPREDUCE-5785:
-------------------------------
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.
> Derive heap size or mapreduce.*.memory.mb automatically
> -------------------------------------------------------
>
> Key: MAPREDUCE-5785
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5785
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Components: mr-am, task
> Reporter: Gera Shegalov
> Assignee: Gera Shegalov
> Fix For: 3.0.0
>
> Attachments: MAPREDUCE-5785.v01.patch, MAPREDUCE-5785.v02.patch,
> MAPREDUCE-5785.v03.patch, mr-5785-4.patch, mr-5785-5.patch, mr-5785-6.patch,
> mr-5785-7.patch, mr-5785-8.patch, mr-5785-9.patch
>
>
> 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.
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