PREEMPTIVE_OS_DEVICEIOCONTROL

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Description:

This wait type is when a thread is calling the Windows DeviceIoControl function.

(Books Online description: N/A)

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Added in SQL Server version:

2008

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 448 in 2008 and 2008 R2, 496 in 2012, and 512 in 2014 RTM. After 2014 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.

Note that when a thread calls out to Windows, the thread changes from non-preemptive (SQL Server controls the thread) to preemptive (Windows controls the thread) mode. The thread’s state will be listed as RUNNING, as SQL Server doesn’t know what Windows is doing with the thread.

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

1. Setting a device IOCTL (in this case, while performing zero initialization of a file)
2. Setting a device IOTCL (in this case, while creating a sparse file as part of a database snapshot)
3. Setting a device IOTCL (in this case, while creating the hidden database snapshot as part of running a DBCC CHECKALLOC)

And other similar call stacks.

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

1. SOS_Task::PopWait+b1
   AutoSwitchPreemptive::~AutoSwitchPreemptive+95
   FCB::ZeroFile+28e
   FCB::InitializeSpace+293
   FileMgr::CreateNewFile+10e
   AsynchronousDiskAction::ExecuteDeferredAction+8f
   AsynchronousDiskWorker::ThreadRoutine+15c
   SubprocEntrypoint+a7f
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab
2. SOS_Task::PopWait+b1
   AutoSwitchPreemptive::~AutoSwitchPreemptive+95
   FCB::MakeFileSparse+126
   FCB::CreatePhysicalFile+755
   FileMgr::CreateNewFile+d9
   AsynchronousDiskAction::ExecuteDeferredAction+8f
   AsynchronousDiskWorker::ThreadRoutine+15c
   SubprocEntrypoint+a7f
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab
3. SOS_Task::PopWait+b1
   AutoSwitchPreemptive::~AutoSwitchPreemptive+95
   FCB::FillSidePageTable+216
   FileMgr::StartPrimaryDataFiles+22d
   FileMgr::StartupPreRecovery+75a
   DBMgr::SyncAndLinkReplicaSetupPhase+a4e
   DBMgr::CreatePhasedTransientReplica+4b6
   DBMgr::CreateTransientReplica+fd
   DBDDLAgent::CreateReplica+183
   UtilDbccCreateReplica+7a
   DbccCheckAlloc+751
   DbccCommand::Execute+153
   CStmtDbcc::XretExecute+7cd
   CMsqlExecContext::ExecuteStmts<1,1>+427
   CMsqlExecContext::FExecute+a43
   CSQLSource::Execute+86c
   process_request+a57
   process_commands+4a3
   SOS_Task::Param::Execute+21e
   SOS_Scheduler::RunTask+ab