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maprfs as dropin replacement for hdfs with hypertable

Question asked by sirpy on Nov 24, 2011
Latest reply on Dec 21, 2011 by doug_judd
We are using hypertable(hypertable.org) as a database (hbase alternative).
I was able to easily change hypertable to work with maprfs instead of hdfs, but i'm now encountring high memory usage by the hypertable DfsBroker which is the service that manages read/write requests from hypertable to the dfs.
when looking at the jmap output of the dfs broker I see many mapr Page objects.but the total memory used is only around 250MB while the resident memory on top shows 3.5G and 12G virtual memory, so my guess is that this is because of memory mapped files(directbytebuffer) by the dfsbroker or maprfs.
This didn't happen when we used hdfs.

do you have any insights on the subject?

what is the Page object? why so many instances?

here is a dump of the top objects seen in jmap.

    1:         17438      143240264  [B
    2:        586965       42261480  com.mapr.fs.Page
    3:        586986       37567104  java.nio.DirectByteBuffer
    4:        594690       14272560  java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject
    5:          1269        5897816  [I
    6:         15903        5040176  [Lcom.mapr.fs.Page;
    7:         34385        3781424  [C
    8:         14249        1948232  <constMethodKlass>
    9:         14249        1717464  <methodKlass>
    10:         1174        1300688  <constantPoolKlass>
    11:        23855        1099800  <symbolKlass>
    12:         1174         885288  <instanceKlassKlass>
    13:         1064         869888  <constantPoolCacheKlass>
    14:         7724         679712  com.mapr.fs.MapRFsInStream
    15:        20974         671168  java.lang.String
    16:         5697         638064  java.lang.Thread
    17:         7731         618480  com.mapr.fs.Inode
    18:         7731         371088  com.mapr.fs.InodeAttributes
    19:          843         357520  <methodDataKlass>
    20:         7724         308960  com.mapr.fs.MapRFsDataInputStream
    21:         9146         292672  java.util.HashMap$Entry
    22:         7998         255936  java.util.concurrent.locks.ReentrantLock$NonfairSync
    23:         7731         247392  com.mapr.fs.Inode$ListElem
    24:         7731         247392  org.hypertable.DfsBroker.hadoop.OpenFileData

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