SLEEP_BPOOL_STEAL

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Description:

This wait type is when a free list stall occurs in the buffer pool. This means that a new page needs to be created but there isn’t any free memory in the buffer pool, so the thread sleeps for a very short period of time (in SQL Server 2005 in was 10ms), assuming that while it is asleep something (e.g. the lazywriter) will free up some memory. When this wait occurs, you will see a blip in the Buffer Manager:Free list stalls/sec perfmon counter.

(Books Online description: N/A)

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Added in SQL Server version:

2019

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 1396 in 2019 CU12. After 2019 CU12, 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, but if they start to increase on your system, that’s a sign that the buffer pool is under memory pressure, which may indicate other problems on the instance.

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

1. Free list stall (in this case, as part of allocating a page for the version store in tempdb)
2. Free list stall (in this case, as part of performing readahead during an index scan)

And other similar call stacks.

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

1. SOS_Task::PostWait+0x6f
   SOS_Task::Sleep+0x140
   BPool::Steal+0x894
   BPool::NewPage+0x78f
   PageRef::FormatInternal+0x83
   AppendOnlyStorageUnit::SetupPageHeaderPreAllocation+0xb9
   AllocationReq::AllocateExtent+0x375
   AllocationReq::AllocatePages+0x151c
   AllocationReq::Allocate+0x144
   AppendOnlyStorageUnit::AllocateNewExtent+0x336
   AppendOnlyVerStoreMgr::AddRecord+0x1464
   VersionMgr::AddRecordToVersionStore+0x79
   VersionMgr::GenerateVersion+0x298b
   IndexPageRef::Modify+0x2522
   BTreeRow::UpdateRecord+0x27c0
   IndexDataSetSession::SetDataInternal+0x72cf
   DatasetSession::SetData+0x2b9
   RowsetNewSS::SetData+0x6a
   CValRow::SetDataX+0x61
   sqlTsEs.dll!CEsExec::GeneralEval4+0xe7
   CQScanSimpleUpdateNew::GetRow+0x16b
   CQScanLightProfileNew::GetRow+0x19
2. SOS_Task::PostWait+0x6f
   SOS_Task::Sleep+0x140
   BPool::Steal+0x894
   BPool::GetFromDisk+0x516
   BPool::ReadAhead+0x119
   IssueReadAheadHelper+0x1fd
   PageReadAhead::ReadAhead+0x3d
   PageReadAhead::Notify+0x145
   KeyRangeGenerator::ReadAhead+0x18b
   KeyRangeGenerator::GetNextRange+0x3c5
   IndexDataSetSession::GetNextRangeForChildScan+0x1cb
   IndexDataSetSession::SetupNextChildSubScan+0x2c4
   IndexDataSetSession::GetBatchInternal+0x5df0
   DatasetSession::GetBatch+0x136
   RowsetNewSS::GetBatch+0x5a
   CBpQScanRowStoreScan::BpFetchNextBatch+0xb7
   CBpQScan::GetNextBatch+0x6f
   CBpChildIteratorScanner::BpGetNextBatch+0x12
   CBpQScanHashAggNew::ProcessInput+0x8b
   CBpQScanHashAggNew::PbsGetForOriginalInputs+0x21
   CBpSpillProcessor::Main+0x113
   CBpQScanHashAggNew::BpGetNextBatch+0x52