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HDFS, mail # user - Re: Child JVM memory allocation / Usage


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Re: Child JVM memory allocation / Usage
Hemanth Yamijala 2013-03-26, 04:42
Hi,

One option to find what could be taking the memory is to use jmap on the
running task. The steps I followed are:

- I ran a sleep job (which comes in the examples jar of the distribution -
effectively does nothing in the mapper / reducer).
- From the JobTracker UI looked at a map task attempt ID.
- Then on the machine where the map task is running, got the PID of the
running task - ps -ef | grep <task attempt id>
- On the same machine executed jmap -histo <pid>

This will give you an idea of the count of objects allocated and size. Jmap
also has options to get a dump, that will contain more information, but
this should help to get you started with debugging.

For my sleep job task - I saw allocations worth roughly 130 MB.

Thanks
hemanth
On Mon, Mar 25, 2013 at 6:43 PM, Nagarjuna Kanamarlapudi <
[EMAIL PROTECTED]> wrote:

> I have a lookup file which I need in the mapper. So I am trying to read
> the whole file and load it into list in the mapper.
>
> For each and every record Iook in this file which I got from distributed
> cache.
>
> —
> Sent from iPhone
>
>
> On Mon, Mar 25, 2013 at 6:39 PM, Hemanth Yamijala <
> [EMAIL PROTECTED]> wrote:
>
>> Hmm. How are you loading the file into memory ? Is it some sort of memory
>> mapping etc ? Are they being read as records ? Some details of the app will
>> help
>>
>>
>> On Mon, Mar 25, 2013 at 2:14 PM, nagarjuna kanamarlapudi <
>> [EMAIL PROTECTED]> wrote:
>>
>>> Hi Hemanth,
>>>
>>> I tried out your suggestion loading 420 MB file into memory. It threw
>>> java heap space error.
>>>
>>> I am not sure where this 1.6 GB of configured heap went to ?
>>>
>>>
>>> On Mon, Mar 25, 2013 at 12:01 PM, Hemanth Yamijala <
>>> [EMAIL PROTECTED]> wrote:
>>>
>>>> Hi,
>>>>
>>>> The free memory might be low, just because GC hasn't reclaimed what it
>>>> can. Can you just try reading in the data you want to read and see if that
>>>> works ?
>>>>
>>>> Thanks
>>>> Hemanth
>>>>
>>>>
>>>> On Mon, Mar 25, 2013 at 10:32 AM, nagarjuna kanamarlapudi <
>>>> [EMAIL PROTECTED]> wrote:
>>>>
>>>>> io.sort.mb = 256 MB
>>>>>
>>>>>
>>>>> On Monday, March 25, 2013, Harsh J wrote:
>>>>>
>>>>>> The MapTask may consume some memory of its own as well. What is your
>>>>>> io.sort.mb (MR1) or mapreduce.task.io.sort.mb (MR2) set to?
>>>>>>
>>>>>> On Sun, Mar 24, 2013 at 3:40 PM, nagarjuna kanamarlapudi
>>>>>> <[EMAIL PROTECTED]> wrote:
>>>>>> > Hi,
>>>>>> >
>>>>>> > I configured  my child jvm heap to 2 GB. So, I thought I could
>>>>>> really read
>>>>>> > 1.5GB of data and store it in memory (mapper/reducer).
>>>>>> >
>>>>>> > I wanted to confirm the same and wrote the following piece of code
>>>>>> in the
>>>>>> > configure method of mapper.
>>>>>> >
>>>>>> > @Override
>>>>>> >
>>>>>> > public void configure(JobConf job) {
>>>>>> >
>>>>>> > System.out.println("FREE MEMORY -- "
>>>>>> >
>>>>>> > + Runtime.getRuntime().freeMemory());
>>>>>> >
>>>>>> > System.out.println("MAX MEMORY ---" +
>>>>>> Runtime.getRuntime().maxMemory());
>>>>>> >
>>>>>> > }
>>>>>> >
>>>>>> >
>>>>>> > Surprisingly the output was
>>>>>> >
>>>>>> >
>>>>>> > FREE MEMORY -- 341854864  = 320 MB
>>>>>> > MAX MEMORY ---1908932608  = 1.9 GB
>>>>>> >
>>>>>> >
>>>>>> > I am just wondering what processes are taking up that extra 1.6GB
>>>>>> of heap
>>>>>> > which I configured for the child jvm heap.
>>>>>> >
>>>>>> >
>>>>>> > Appreciate in helping me understand the scenario.
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> > Regards
>>>>>> >
>>>>>> > Nagarjuna K
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Harsh J
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Sent from iPhone
>>>>>
>>>>
>>>>
>>>
>>
>
+
nagarjuna kanamarlapudi 2013-03-26, 04:53
+
Hemanth Yamijala 2013-03-26, 15:53
+
Koji Noguchi 2013-03-26, 16:11
+
nagarjuna kanamarlapudi 2013-03-27, 08:28
+
Hemanth Yamijala 2013-03-27, 08:59