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https://issues.apache.org/jira/browse/HADOOP-5883?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hemanth Yamijala updated HADOOP-5883:
-------------------------------------
Attachment: HADOOP-5883.patch
The attached patch file incorporates the changes as mentioned in the earlier
comment.
The key change was to determine processes older than a certain time. To do
this, the process tree class keeps track of an 'age' of the process - which is
how many time the process tree has seen a process with this PID. This count is
updated every time the process tree is refreshed - which is once every
monitoring iteration. The monitoring thread can now ask for cumulative virtual
memory of processes over a certain 'age'. For the sake of simplicity, I've
assumed the monitoring interval determines how aged processes are.
It is possible to do something more sophisticated - for e.g. we could determine
the walltime of the process by making a system call. There doesn't seem to be a
direct API for getting the 'walltime' of a process. One hack would be to see
the created time of the pid directory in /proc and then subtract it from
timeofday each time. However, it seems like this could be a costly operation,
while not giving way too much more accuracy.
Summary of the changes:
- TaskMemoryManagerThread: changes to the logic to determine if a task is over
limit.
- ProcfsBasedProcessTree: introduces age for processes and updates them
- The rest of the changes were a lot to do with enabling fast unit tests to be
written. I think it is a good idea to move many of the tests for these two
classes to use the testing mechanism I'm using. But that's the focus of another
JIRA.
- Introduced new tests for testing just these changes.
I suppose this patch will need merging with HADOOP-5881, which is likely to go
in first. I will update the patch with those changes once it's ready. This is
just put up for early consumption.
Also missing is documentation updates for the new semantics of monitoring.
Again, I will finish that after the HADOOP-5881 merge.
> TaskMemoryMonitorThread might shoot down tasks even if their processes
> momentarily exceed the requested memory
> --------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-5883
> URL: https://issues.apache.org/jira/browse/HADOOP-5883
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Hemanth Yamijala
> Attachments: HADOOP-5883.patch
>
>
> Currently the TaskMemoryMonitorThread kills tasks as soon as it detects they
> are consuming more memory than the max value specified. There are valid cases
> (see HADOOP-5059) where if a program is executed from the task, it might
> momentarily occupy twice the amount of memory for a short time. Ideally the
> monitoring thread should handle this case.
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