IRQL Level

Question

Is it possible to change the IRQL level of my program?

Answer 1

Hi,

What do you call the IRQ level of your program ?  Do you mean the "process priority" ? It's possible but unless you have particular needs this is likely the last thing you should try (i.e. if this is for performance issue, it would be better to fix those).

I would suggest to just tell what you are trying to do rather than asking about how you expect this to be done.

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Please always mark whatever response solved your issue so that the thread is properly marked as "Answered".

Answer 2

I need to create a system thread in Visual Basic for my business application.

I thought IRQL was the same thing...

Answer 3

if you want to run a thread, use the framework runtime, as described here:

http://msdn.microsoft.com/en-us/library/3e8s7xdd%28v=vs.100%29.aspx

IRQs, are a hardware/driver/kernel mechanism/interface that allows hardware and software to share events. they are still important, but not to the vast majority of programmers. it is essential to native driver and kernel development though.

Answer 4

Yes, that is what I'm doing. I need to make my application act as if it's a driver. (It technically is)

I need very high priorities. Realtime/Time_Critical are not enough.

Answer 5

Yes, that is what I'm doing. I need to make my application act as if it's a driver. (It technically is)

I need very high priorities. Realtime/Time_Critical are not enough.

Then VB is not the rigth choice because it creates application running in user mode.

Windows Driver Kit:
http://msdn.microsoft.com/en-us/library/ff557573(VS.85).aspx

Unfortunatelly the topic "Choosing a Programming Language" has been removed from the SDK. It said: "For maximum portability, drivers should be written in a high-level language, typically C for kernel-mode drivers, and C or C++ for user-mode drivers."

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Armin

Answer 6

So is it not possible to do this, or is there any other way to obtain high-level rights for my program? Anything better than priorities in visual basic?

Answer 7

Priorities for user mode processes and threads are not VB or .Net specific. It is what Windows offers.
http://msdn.microsoft.com/en-us/library/ms685100(VS.85).aspx

Maybe we can help you without writing a driver if you tell us what you're trying to do. So...?

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Armin

Answer 8

Thank you for your reply. Just two more questions.

Does this code allow my program to only run on one CPU? (The 2nd CPU)

ProcessorAffinity = CType(2,IntPtr)

And, does anyone know of any windows processes that are run as realtime processes?

Answer 9

Yes.

In the task manager, show "[x] processes of all users", display the colum "base priority" and sort by it.

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Armin

Answer 10

Thank you.

One last question. Hardware/Drivers are usually ran as RealTime Priority, Correct? So, just the windows processes will appear in the task manager. There are no realtime windows processes, but there are realtime drivers that are invisible?

Answer 11

This is handled specially in kernel mode. I don't know much about this. Maybe this helps: http://msdn.microsoft.com/en-us/library/ff564638(VS.85).aspx

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Armin

Answer 12

Wow, that link is perfect. Thanks! And, sorry, but, just ONE more question. I'm calling SetThreadPriority API, but it's not setting the thread priority.

Private Declare Function SetThreadPriority Lib "kernel32" (ByVal hThread As
IntPtr, ByVal nPriority As Integer) As Integer

SetThreadPriority(Thread.ManagedThreadId,

ThreadPriorityLevel.AboveNormal)

However, when I call the:

Dim

Test = CurrentProcess.BasePriority

        MsgBox(Test)

I still receive "24". 24 is the normal thread priority at Realtime process. I have it at AboveNormal, so it should say something above 24.

Any ideas?

Answer 13

You don't have to call the API to set the priority. Just set the priority property of the Thread object:

System.Threading.Thread.CurrentThread.Priority = Threading.ThreadPriority.AboveNormal

You must not pass the managed thread ID to SetThreadPriority as it expects a thread handle. That's something different. In theory, the runtime can change the system thread in which the managed thread is running, that's why there is a managed thread ID that does not change. If you wanted to call SetThreadPriority for the current thread you'd have to call API function GetCurrentThread() before, and before that, you'd have to call Thread.BeginThreadAffinity. Long story short:

Imports System.Threading
Imports AZ.Win32

Public Class Main

   Shared Sub Main()

      Thread.BeginThreadAffinity()

      Try
         Dim h = Functions.GetCurrentThread()
         Functions.SetThreadPriority(h, AZ.Win32.ThreadPriority.AboveNormal)
         '...
         Functions.SetThreadPriority(h, AZ.Win32.ThreadPriority.Normal)
      Finally
         Thread.EndThreadAffinity()
      End Try

   End Sub

End Class

I don't post the declarations as it's only for demonstration.

But again, API calls are not required.

Don't mix up the priority class of the process with the priorty of the thread. By setting the latter you don't change the former. Both values are combined for each thread to the base priority as shown in the table in the link I posted some messages ago. The property CurrentProcess.BasePriority is something different again. Actually I haven't come across it yet. As it's readonly, just stick with the thread's Priority property and the PriortyClass property of the process object.

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Armin

Answer 14

Thanks, I understand.

I'm using Visual Basic 2010, so Imports Az.Win32 doesn't exist. Also, your current SetThreadPriority only goes as high as "highest". There is no TIME_CRITICAL option.

What should I do?

Answer 15

Sure az.win32 doesn't exist as it's in my own library, but as I said it's not required to show declarations.

"What should I do?"

Tell us what you're trying to do. You don't need to set anything to time_critical, and if you still think you have to, you have to write a driver.

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Armin

Answer 16

Sure az.win32 doesn't exist as it's in my own library, but as I said it's not required to show declarations.

"What should I do?"

Tell us what you're trying to do. You don't need to set anything to time_critical, and if you still think you have to, you have to write a driver.

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Armin

Can you post an example code for changing the priority to time_critical without using your own library? The last request. :)

Answer 17

Can you post an example code for changing the priority to time_critical without using your own library? The last request. :)

Just pick out the right declarations and values. I don't think it's necessary, so I won't post it.

You may be able to lock a foreign system.

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Armin

Answer 18

I have:

Private Declare Function GetCurrentThread Lib "kernel32" Alias "GetCurrentThread" () As Integer

Private Declare Function SetThreadPriority Lib "kernel32" (ByVal hThread As IntPtr, ByVal nPriority As Integer) As Integer

   Public Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Thread = New System.Threading.Thread(AddressOf Superior)
        Thread.Start()
    End Sub

    Public Sub Superior()
        Thread.BeginThreadAffinity()
Dim CurrentThread = GetCurrentThread()
        SetThreadPriority(CurrentThread, ThreadPriorityLevel.TimeCritical)

Dim Test = CurrentProcess.BasePriority
        MsgBox(Test)

Yet, my base priority still says 24.

Answer 19

Hi, you set the priority of a background thread and you read the priority of your process. Never done that but could it be the issue ?

From what I see you could also perhaps just try http://msdn.microsoft.com/en-us/library/system.diagnostics.process.priorityclass.aspx instead which is a read/write property ?

Finally as hinted by Armin, it's hard to give an advice without knowing what is the problem you are trying to solve. Sometimes it allows one to suggest an alternate better solution or even to avoid wasting time by finding out that the current worked on solution just won't cut it.

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Please always mark whatever response solved your issue so that the thread is properly marked as "Answered".

Answer 20

Hi, you set the priority of a background thread and you read the priority of your process. Never done that but could it be the issue ?

From what I see you could also perhaps just try http://msdn.microsoft.com/en-us/library/system.diagnostics.process.priorityclass.aspx instead which is a read/write property ?

Finally as hinted by Armin, it's hard to give an advice without knowing what is the problem you are trying to solve. Sometimes it allows one to suggest an alternate better solution or even to avoid wasting time by finding out that the current worked on solution just won't cut it.

---

Please always mark whatever response solved your issue so that the thread is properly marked as "Answered".

I'm just trying to set my base priority to the maximum (31).

This should be all I need to do for my program.

The base priority is the combined priority of my thread and process priority. So, since I called the GetBasePriority function during my main thread (Superior) - after I used SetThreadPriority - it should have given me my desired base priority.

So, how can I achieve a Base Priority of 31?

Answer 21

I ran the GetThreadPriority function and it gave me '15'. My process is set to realtime. It seems to me that 'SetThreadPriority' doesn't seem to be working at all. I even tried using it with 'GetCurrentThread'.

I don't understand.

Answer 22

Show us the code that doesn't seem to work.

Don't care about Process.BasePriority. Use Thread.Priority and Process.PriorityClass. If it makes you happy, you can use SetThreadPriority to the set thread priority to time critical which is not available in System.Threading.ThreadPriority.

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Armin

Answer 23

Show us the code that doesn't seem to work.

Don't care about Process.BasePriority. Use Thread.Priority and Process.PriorityClass. If it makes you happy, you can use SetThreadPriority to the set thread priority to time critical which is not available in System.Threading.ThreadPriority.

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Armin

Thank you for this reply. :)

I used Process.PriorityClass and set my current process to realtime. This works. :)

As above posted, I used GetCurrentThread, then GetThreadPriority, then SetThreadPrioirty and it gave me a priority of 15. Well, there is no 15 priority for a realtime process, so I don't know what's wrong. :(

My multithreading code is posted above. I used SetThreadPriority right after I started my thread.

Answer 24

The declaration of GetCurrentThread is wrong. Return type must be IntPtr. I can not compile it. Always use Option Strict On.

"Well, there is no 15 priority for a realtime process, so I don't know what's wrong."

The name is GetThreadPriority and SetThreadPrioirty. The valid range is -15..15, so I don't see the problem.

A process has a priority class. It must be one of the predefined values (Idle, Normal, etc.) It's value has no relation to the thread priority.

Both values, the priority class of the process and the priority of the thread, form the base priority of the thread as shown in the linked table.

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Armin

Answer 25

The declaration of GetCurrentThread is wrong. Return type must be IntPtr. I can not compile it. Always use Option Strict On.

"Well, there is no 15 priority for a realtime process, so I don't know what's wrong."

The name is GetThreadPriority and SetThreadPrioirty. The valid range is -15..15, so I don't see the problem.

A process has a priority class. It must be one of the predefined values (Idle, Normal, etc.) It's value has no relation to the thread priority.

Both values, the priority class of the process and the priority of the thread, form the base priority of the thread as shown in the linked table.

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Armin

Thanks, I changed it to IntPtr.

No, the value range is -15-15 if you have a priority other than realtime class.

Realtime classes start at 16 thread priority and go up to 31. (31 is what I need):

http://msdn.microsoft.com/en-us/library/windows/desktop/ms685100(v=vs.85).aspx

Yes, I know, I set my process priority to realtime.

Yes, I know, my current base priority is 24. It needs to be 31.

Answer 26

http://msdn.microsoft.com/en-us/library/windows/desktop/ms685100(v=vs.85).aspx

You do not set or query the value in the 3rd column. You set/query the value in the 2nd column. It is always -15..15 no matter what value you have in the first column.

EDIT: the value in the 3rd column is the result of the combination of the first and second column. This is done by the system, not by yourself. You can not set the value in the 3rd column, and AFAIK you can also not retrieve it. But it doesn't matter because you only care about 1st and 2nd column. The rest is done by the system.

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Armin

Answer 27

http://msdn.microsoft.com/en-us/library/windows/desktop/ms685100(v=vs.85).aspx

You do not set or query the value in the 3rd column. You set/query the value in the 2nd column. It is always -15..15 no matter what value you have in the first column.

EDIT: the value in the 3rd column is the result of the combination of the first and second column. This is done by the system, not by yourself. You can not set the value in the 3rd column, and AFAIK you can also not retrieve it. But it doesn't matter because you only care about 1st and 2nd column. The rest is done by the system.

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Armin

If I set my process to realtime and my thread priority to time critical it should give me a base priority of 31.

It doesn't.

You programmatically set your thread/process priority and then windows will automatically combine the values and form your base priority.

Obviously, SetThreadPriority isn't working.

Answer 28

If I set my process to realtime and my thread priority to time critical it should give me a base priority of 31.

It doesn't.

As there is no function to return a thread's base priorty (the 3rd column), you can not make such a statement.

Are you're still referring to Process.BasePriority? It's obviously process specific whereas a thread's base priority is thread specific. You can not use that value to make a statement about the base priorty of a certain thread. Process.BasePriority has a different meaning. As I said, just ignore it, or read the documentation about it.

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Armin

Answer 29

So what you're saying is, the code you provided works fine?

Just use ThreadBeginAffinity?

Answer 30

You don't have to call the API to set the priority. Just set the priority property of the Thread object:

System.Threading.Thread.CurrentThread.Priority = Threading.ThreadPriority.AboveNormal

You must not pass the managed thread ID to SetThreadPriority as it expects a thread handle. That's something different. In theory, the runtime can change the system thread in which the managed thread is running, that's why there is a managed thread ID that does not change. If you wanted to call SetThreadPriority for the current thread you'd have to call API function GetCurrentThread() before, and before that, you'd have to call Thread.BeginThreadAffinity. Long story short:

Imports System.Threading
Imports AZ.Win32

Public Class Main

   Shared Sub Main()

      Thread.BeginThreadAffinity()

      Try
         Dim h = Functions.GetCurrentThread()
         Functions.SetThreadPriority(h, AZ.Win32.ThreadPriority.AboveNormal)
         '...
         Functions.SetThreadPriority(h, AZ.Win32.ThreadPriority.Normal)
      Finally
         Thread.EndThreadAffinity()
      End Try

   End Sub

End Class

I don't post the declarations as it's only for demonstration.

But again, API calls are not required.

Don't mix up the priority class of the process with the priorty of the thread. By setting the latter you don't change the former. Both values are combined for each thread to the base priority as shown in the table in the link I posted some messages ago. The property CurrentProcess.BasePriority is something different again. Actually I haven't come across it yet. As it's readonly, just stick with the thread's Priority property and the PriortyClass property of the process object.

---

Armin

Dim CurrentThread = System.Threading.Thread.CurrentThread

Public Sub Main()

Thread.BeginThreadAffinity

'Code

Thread.EndThreadAffinity

End Sub

Private Sub Button1_Click

'Create New Thread

'Start Thread

SetThreadPriority(CurrentThread, ThreadPriorityLevel.TimeCritical)

End Sub

I can't get this working at all. ThreadAffinity works fine, but setting the thread priority to Time Critical won't work. :(

Can someone please post the code, so I can get past this...

Answer 31

How do you know it fails? Did you check the return value of SetThreadPriority? If it's true, it succeeded. Did you call GetThreadPriority afterwards? If it returns TimeCritical you also know that it was successful. Just tried it and it works.

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Armin

Answer 32

How do you know it fails? Did you check the return value of SetThreadPriority? If it's true, it succeeded. Did you call GetThreadPriority afterwards? If it returns TimeCritical you also know that it was successful. Just tried it and it works.

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Armin

Post the code that you tried?

Answer 33

Almost the same I already posted.

Imports System.Threading
Imports AZ.Win32

Public Class Main

   Shared Sub Main()

      Thread.BeginThreadAffinity()

      Try
         Dim h = Functions.GetCurrentThread()

         If Functions.SetThreadPriority(h, AZ.Win32.ThreadPriority.TimeCritical) Then
            Try
               MsgBox(Functions.GetThreadPriority(h).ToString)
            Finally
               If Not Functions.SetThreadPriority(h, AZ.Win32.ThreadPriority.Normal) Then
                  Throw New System.ComponentModel.Win32Exception("Error at SetThreadPriority")
               End If
            End Try
         Else
            Throw New System.ComponentModel.Win32Exception("Error at SetThreadPriority")
         End If
      Finally
         Thread.EndThreadAffinity()
      End Try

   End Sub

End Class

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Armin

Answer 34

This is my code. I don't get any errors running it, but I don't know if the thread priority is actually time critical:

Imports System.Threading

Private Declare Function SetThreadPriority Lib "kernel32" (ByVal hThread As IntPtr, ByVal nPriority As Integer) As Integer

Private Declare Function GetCurrentThread Lib "kernel32" () As IntPtr

Dim CurrentProcess As Process = Process.GetCurrentProcess

Dim Thread As System.Threading.Thread
    Dim CurrentThread = GetCurrentThread()

'Form Load
CurrentProcess.PriorityClass = ProcessPriorityClass.RealTime

'Button Click
 Thread = New System.Threading.Thread(AddressOf Sub)
        Thread.Start()
        SetThreadPriority(CurrentThread, ThreadPriorityLevel.TimeCritical)

'Sub
 Thread.BeginThreadAffinity()

'My Code

Thread.EndThreadAffinity()

 Is this the way I'm supposed to set it up? Btw, thank you for all your time in helping me do this. I can promise you that I would have never found out how to work this stuff without your help. :)

Answer 35

This is my code. I don't get any errors running it, but I don't know if the thread priority is actually time critical:

Call GetThreadPriority to find it out.

Your code sets the priority of the current thread, not of the started thread.

This is my last post about this issue.

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Armin

Answer 36

You never posted how to change the priority of the started thread.

And, how am I supposed to get it right, if you're using your own functions in your examples? I'm just back at square one.

I just want a time_critical thread. (My thread)

Answer 37

• "You never posted how to change the priority of the started thread."

Right, because you last example was the first one that was meant to set the priority from the starting thread, not within the started thread. The code in your previous message containing code wasn't compilable so I ignored it and posted my code (that you've asked for).

• "And, how am I supposed to get it right, if you're using your own functions in your examples?"

Can't I suppose you've declared your own functions and use them? How else could you have ran your tests? Howe can you say it doesn't work if you don't have functions to call?

• "I just want a time_critical thread."

Call SetThreadPriority and pass TimeCritical. The answer won't change. Neither you believe me that it works, nor you trust the return value of SetThreadPriorty, nor the return value of GetThreadPriority, so what can I add?

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Armin

Answer 38

• "You never posted how to change the priority of the started thread."

Right, because you last example was the first one that was meant to set the priority from the starting thread, not within the started thread. The code in your previous message containing code wasn't compilable so I ignored it and posted my code (that you've asked for).

• "And, how am I supposed to get it right, if you're using your own functions in your examples?"

Can't I suppose you've declared your own functions and use them? How else could you have ran your tests? Howe can you say it doesn't work if you don't have functions to call?

• "I just want a time_critical thread."

Call SetThreadPriority and pass TimeCritical. The answer won't change. Neither you believe me that it works, nor you trust the return value of SetThreadPriorty, nor the return value of GetThreadPriority, so what can I add?

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Armin

Why can't you just post fully-working code? It would have saved us days of time...

It's much easier to learn by reading example code then it is to google how to do things.

Answer 39

I did post full working  code. You already have the declarations, so just use them. Your problem aren't missing declarations, it's a lack of acceptance.

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Armin