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MEMORY_ALLOCATION_EXT

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Description:

This wait type is when a thread is switching to preemptive mode while allocating memory. The preemptive switch is so that the code being executed does not have to check for quantum exhaustion.

(Books Online description: N/A)

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Added in SQL Server version:

2016

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 1100 in 2016 RTM. After 2016 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

I have not seen this wait type be a noticeable contention point.

Known occurrences in SQL Server (list number matches call stack list):

  1. Allocating memory (in this case, while running the background FILESTREAM garbage collector)
  2. Allocating memory (in this case, while creating a new page to hold a blob value)
  3. Allocating memory (in this case, while creating a new page as part of a page split operation)

And many more similar call stacks.

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PopWait+0xb4
    MemoryClerkInternal::AllocatePagesWithFailureMode+0x18c
    MemoryClerkInternal::AllocatePages+0x2b
    CMemThread<CMemObj>::PbGetNewPages+0x63
    TVarPageMgr<0>::PviNewVarPage+0x36
    TVarPageMgr<0>::PbAllocate+0x1dd
    CMemThread<CMemObj>::Alloc+0xa8
    SetFilter+0x5bd
    IndexDataSetSession::SetFilterInternal+0x6e
    RowsetNewSS::SetFilter+0x2f0
    CMEDScan::StartSearch+0x492
    CMIterObjects::StartIteration+0x2b1
    FsTombstoneTableAccessor::Open+0xe2
    FsGarbageCollector::CollectGarbageIteration+0x23a
    FsGarbageCollector::CollectGarbage+0x128
    FsGarbageCollector::ProcessFsGarbageCollectionForDB+0x381
    FsGarbageCollector::ProcessFsGarbageCollection+0x22f
    PeriodicTimerTask::ProcessTskPkt+0x79
    TaskReqPktTimer::ExecuteTask+0x69
    OnDemandTaskContext::ProcessTskPkt+0x31f
    SystemTaskEntryPoint+0x3d2
    OnDemandTaskContext::FuncEntryPoint+0x25
  2. SOS_Task::PopWait+0xb4
    MemoryClerkInternal::AllocatePagesWithFailureMode+0x18c
    MemoryClerkInternal::AllocatePages+0x22
    BPool::Steal+0x52b
    BPool::NewPage+0x661
    PageRef::FormatInternal+0x83
    CompactSpaceAllocator::AllocateAndFixPage+0x4b9
    CompactSpaceAllocator::AllocateAndFixPageInternal+0xb1
    CompactSpaceAllocator::FindSpaceAndFixPage+0x144
    BlobBase::AllocDataNode+0x284
    Blob::InsertNonFull+0x2e4
    Blob::InsertWholePage+0x159
    Blob::Insert+0x236
    BlobManager::ReplaceAtWithILB+0x59b
    LockBytesSS::ReplaceAtWithILB+0x17
    CMainIlb::ReplaceAtWithILB+0x90
    CBlobHandleFactories::CopyIlbRaiseError+0x70
    CBlobHandleHelper::CopyBlobHandleIntoTempOrInlined+0x1ff
    CBlobHandleManagerCommon::PxvarPreprocessInternal+0x11b
    CValRowNoHrow::SetDataX+0x28
    CEsExec::FastMoveEval+0x160
    CQScanSortNew::PushRow+0x2e
  3. SOS_Task::PopWait+0xb4
    MemoryClerkInternal::AllocatePagesWithFailureMode+0x18c
    MemoryClerkInternal::AllocatePages+0x22
    BPool::Steal+0x52b
    BPool::NewPage+0x661
    PageRef::SetupPageHeaderPreAllocation+0x65
    SetupPageHeaderPreAllocation+0x6c
    TargetExtentMgr::AllocPageFromTargetExtent+0x5e4
    AllocationReq::AllocateFromExistingExtents+0xa39
    AllocationReq::AllocatePages+0xdac
    AllocationReq::Allocate+0xf3
    AllocateHoBtDataPage+0x5e8
    IndexPageManager::AllocatePage+0x1ad
    SplitPage+0x8d8
    IndexDataSetSession::InsertSmallRecord+0x1b09
    IndexDataSetSession::InsertRowInternal+0x20dc
    DatasetSession::InsertRow+0x2de
    RowsetNewSS::InsertRow+0x26
    CBlobHandleFactoryMain::CreateNewBlobHandleInternal+0x1e7
    CBlobHandleFactoryMain::CreateNewBlobHandle+0x88
    CBlobHandleHelper::CopyBlobHandleIntoTempOrInlined+0x1d3
    CBlobHandleManagerCommon::PxvarPreprocessInternal+0x11b