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HBase, mail # dev - Sporadic memstore slowness for Read Heavy workloads


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Re: Sporadic memstore slowness for Read Heavy workloads
Ted Yu 2014-01-26, 21:56
On a second look, this is the bold line:

org.apache.hadoop.hbase.regionserver.StoreScanner.
next(StoreScanner.java:411)*
On Sun, Jan 26, 2014 at 1:43 PM, Ted Yu <[EMAIL PROTECTED]> wrote:

> I don't see bold line.
> Is the following line what you referred to ?
> org.apache.hadoop.hbase.regionserver.MemStore$MemStoreScanner.reseek(
> MemStore.java:805)
>
> BTW I assume you're using 0.94 HBase in production.
>
> Cheers
>
>
> On Sun, Jan 26, 2014 at 1:17 PM, Varun Sharma <[EMAIL PROTECTED]> wrote:
>
>> Here is the hotthread result. The line in bold is "SEEK_NEXT_COL" and it
>> degenerates to a reseek+skiplist lookup when it does not have to because
>> we
>> already seeked to the row and getting all the columns is just a matter of
>> iterator.next() calls.
>>
>>
>>
>> org.apache.hadoop.hbase.KeyValue$KeyComparator.compareWithoutRow(KeyValue.java:2196)
>>
>> org.apache.hadoop.hbase.KeyValue$KeyComparator.compare(KeyValue.java:2086)
>>
>> org.apache.hadoop.hbase.KeyValue$KVComparator.compare(KeyValue.java:1535)
>>
>> org.apache.hadoop.hbase.KeyValue$KVComparator.compare(KeyValue.java:1523)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$ComparableUsingComparator.compareTo(ConcurrentSkipListMap.java:606)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap.findPredecessor(ConcurrentSkipListMap.java:685)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap.findNear(ConcurrentSkipListMap.java:1345)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$SubMap.loNode(ConcurrentSkipListMap.java:2583)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$SubMap.access$300(ConcurrentSkipListMap.java:2486)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$SubMap$SubMapIter.<init>(ConcurrentSkipListMap.java:3022)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$SubMap$SubMapValueIterator.<init>(ConcurrentSkipListMap.java:3092)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$SubMap.valueIterator(ConcurrentSkipListMap.java:3002)
>>
>>
>> java.util.concurrent.ConcurrentSkipListMap$Values.iterator(ConcurrentSkipListMap.java:2402)
>>
>>
>> org.apache.hadoop.hbase.regionserver.KeyValueSkipListSet.iterator(KeyValueSkipListSet.java:87)
>>
>>
>> org.apache.hadoop.hbase.regionserver.MemStore$MemStoreScanner.reseek(MemStore.java:805)
>>
>>
>> org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner.doRealSeek(NonLazyKeyValueScanner.java:54)
>>
>>
>> org.apache.hadoop.hbase.regionserver.KeyValueHeap.generalizedSeek(KeyValueHeap.java:320)
>>
>>
>> org.apache.hadoop.hbase.regionserver.KeyValueHeap.reseek(KeyValueHeap.java:265)
>>
>>
>> org.apache.hadoop.hbase.regionserver.StoreScanner.reseek(StoreScanner.java:545)
>>
>> *
>>
>> org.apache.hadoop.hbase.regionserver.StoreScanner.next(StoreScanner.java:411)*
>>
>> org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:143)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:3884)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:3956)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:3827)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:3808)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:3851)
>>     org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:4777)
>>     org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:4750)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegionServer.get(HRegionServer.java:2152)
>>
>>
>> org.apache.hadoop.hbase.regionserver.HRegionServer.multi(HRegionServer.java:3700)
>>
>>
>>
>> On Sun, Jan 26, 2014 at 1:14 PM, Varun Sharma <[EMAIL PROTECTED]>
>> wrote:
>>
>> > Hi,
>> >
>> > We are seeing some unfortunately low performance in the memstore - we
>> have
>> > researched some of the previous JIRA(s) and seen some inefficiencies in
>> the
>> > ConcurrentSkipListMap. The symptom is a RegionServer hitting 100 % cpu