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2877735 - High CPU load on HANA during DMO migration

Symptom

High CPU load is observed on HANA during the downtime phase of a DMO migration from source database using the SUM tool.

The DMO utilizes R3load processes which are responsible to export all data from the source database and inserts that data into the SAP HANA Database target.

  • CPU Utilization is reaching 100% utilized, 0.00% Idle.
  • SAP Migration processes are getting terminated using the SUM tool -  DMO (Software Update Manager – Data  Migration Option)
  • The R3load processes are reduced to as low as 10, however the CPU % consumption stays the same.
  • Runtime dump traces on the Indexserver & callstack modules from a kernel trace reveal the top consumers are the number of parallel threads in the optimization compression run phases :
        AttributeEngine::RowOrderOptimizer::determineValueIdCounts
        AttributeEngine::SortRestRangeJob::run




Multiple jobworker callstacks in the optimization compression phase of a delta merge

[thr=100970]: JobWrk73401 at
1: 0x00007f2be99b6527 in AttributeEngine::RowOrderOptimizer::determineValueIdCounts(int, ltt::vector<AttributeEngine::ValueIdCount>&, ltt::vector<int> const&, unsigned int, unsigned int, ltt::vector<int>&)+0xd3 at RowOrderOptimizer.cpp:118 (libhdbcs.so)
2: 0x00007f2be99c452e in AttributeEngine::SortRestRangeJob::run()+0x1ca at ClusterFValueOptimizer.cpp:397 (libhdbcs.so)
3: 0x00007f2bd575a632 in TRexUtils::Parallel::JobBase::runEx()+0x20 at ParallelDispatcher.cpp:194 (libhdbbasement.so)
4: 0x00007f2bd57581d1 in TRexUtils::Parallel::JobBase::run(Execution::Context&, Execution::JobObject&)+0x40 at ParallelDispatcher.cpp:225 (libhdbbasement.so)
5: 0x00007f2bd094d338 in Execution::JobObjectImpl::run(Execution::JobWorker*)+0x2174 at JobExecutorImpl.cpp:1157 (libhdbbasis.so)
6: 0x00007f2bd0937337 in Execution::JobWorker::runJob(ltt::smartptr_handle<Execution::JobObjectForHandle>&)+0x313 at JobExecutorThreads.cpp:381 (libhdbbasis.so)
7: 0x00007f2bd0939195 in Execution::JobWorker::run(void*&)+0xd51 at JobExecutorThreads.cpp:1278 (libhdbbasis.so)
8: 0x00007f2bd08f74e8 in Execution::Thread::staticMainImp(Execution::Thread*)+0x534 at Thread.cpp:529 (libhdbbasis.so)
9: 0x00007f2bd08e6798 in Execution::pthreadFunctionWrapper(Execution::Thread*)+0x164 at ThreadInterposition.cpp:633 (libhdbbasis.so)
10: 0x00007f2bd0079569 in start_thread+0xd5 (libpthread.so.0)
11: 0x00007f2bce8c0a2f in __GI___clone+0x3b (libc.so.6)

 

These jobworker threads are triggered by a mergedogmerger thread for the delta merge 

[thr=49565]: MergedogMerger, TID: 44, UTID: 5154963, CID: -1, LCID: 0, SEID: 844437821433970, parent: 11855

 

[thr=118555]: MergedogMonitor at
1: 0x00007f2bce8bb2a9 in syscall+0x15 (libc.so.6)
2: 0x00007f2bd06a4739 in Synchronization::BinarySemaphore::timedWait(unsigned long, Execution::Context&)+0x255 at LinuxFutexOps.hpp:46 (libhdbbasis.so)
3: 0x00007f2bd5854838 in TrexThreads::Thread::join(int)+0x114 at Thread.cpp:211 (libhdbbasement.so)
4: 0x00007f2be1d1d0ce in TRexAPI::Mergedog::checkAutomerge(TRexAPI::MergedogThr&)+0x168a at Mergedog.cpp:819 (libhdbcsapi.so)
5: 0x00007f2be1d1fa37 in TRexAPI::MergedogWatchThr::run(void*)+0x143 at Mergedog.cpp:133 (libhdbcsapi.so)
6: 0x00007f2bd585fd8b in TrexThreads::PoolThread::run()+0x787 at PoolThread.cpp:462 (libhdbbasement.so)
7: 0x00007f2bd5862850 in TrexThreads::PoolThread::run(void*&)+0x10 at PoolThread.cpp:143 (libhdbbasement.so)
8: 0x00007f2bd08f74e8 in Execution::Thread::staticMainImp(Execution::Thread*)+0x534 at Thread.cpp:529 (libhdbbasis.so)
9: 0x00007f2bd08e6798 in Execution::pthreadFunctionWrapper(Execution::Thread*)+0x164 at ThreadInterposition.cpp:633 (libhdbbasis.so)
10: 0x00007f2bd0079569 in start_thread+0xd5 (libpthread.so.0)
11: 0x00007f2bce8c0a2f in __GI___clone+0x3b (libc.so.6)


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Environment

 SAP HANA Database Platform 1.0

SAP HANA Database Platform 2.0

Product

SAP HANA, platform edition all versions

Keywords

KBA , HAN-DB , SAP HANA Database , Problem

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