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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Windows Development’ Category

Windows: batch file to logoff all other users (run as Administrator)

Posted by jpluimers on 2021/07/22

Based on zzz but filters current user, and listener session.

:: The findstr bit filters out the current session (starts with ">") and session 65536 (which is the listener)
for /f "skip=2 tokens=2,3 delims= " %%a in ('query session ^| findstr /v /b ">" ^| findstr /v "65536  Listen"') DO (
    echo %%a|findstr /xr "[1-9][0-9]* 0" >nul && (
      logoff %%a 
    echo %%b|findstr /xr "[1-9][0-9]* 0" >nul && (
      logoff %%b 
goto :eof


Posted in Batch-Files, Development, Scripting, Software Development, Windows Development | Leave a Comment »

SetProcessWorkingSetSize: you hardly – if ever – need to call this from your process

Posted by jpluimers on 2021/07/07

There are quite a few posts that recommend using SetProcessWorkingSetSize to trim your process working set, usually in the SetProcessWorkingSetSize(ProcessHandle, -1, -1) form:

[WayBack] SetProcessWorkingSetSize function (winbase.h) | Microsoft Docs

Sets the minimum and maximum working set sizes for the specified process.

BOOL SetProcessWorkingSetSize(
  HANDLE hProcess,
  SIZE_T dwMinimumWorkingSetSize,
  SIZE_T dwMaximumWorkingSetSize );

The working set of the specified process can be emptied by specifying the value (SIZE_T)–1 for both the minimum and maximum working set sizes. This removes as many pages as possible from the working set. The [WayBack] EmptyWorkingSet function can also be used for this purpose.

In practice you hardly ever have to do this, mainly because this will write – regardless of (dis)usage – all of your memory to the pagefile, even the memory your frequently use.

Windows has way better heuristics to do that automatically for you, skipping pages you frequently use.

It basically makes sense in a few use cases, for instance when you know that most (like 90% or more) of that memory is never going to be used again.

Another use case (with specific memory sizes) is when you know that your program is going to use a defined range of memory, which is outside what Windows will heuristically expect from it.

A few more links that go into more details on this:

  • [WayBack] windows – Pros and Cons of using SetProcessWorkingSetSize – Stack Overflow answers by:
    • Hans Passant:

      SetProcessWorkingSetSize() controls the amount of RAM that your process uses, it doesn’t otherwise have any affect on the virtual memory size of your process. Windows is already quite good at dynamically controlling this, swapping memory pages out on demand when another process needs RAM.

      By doing this manually, you slow down your program a lot, causing a lot of page faults when Windows is forced to swap the memory pages back in.

      SetProcessWorkingSetSize is typically used to increase the amount of RAM allocated for a process. Or to force a trim when the app knows that it is going to be idle for a long time. Also done automatically by old Windows versions when you minimize the main window of the app.

    • Zack Yezek:

      The only good use case I’ve seen for this call is when you KNOW your process is going to hog a lot of the system’s RAM and you want to reserve it for the duration. You use it to tell the OS “Yes, I’m going to eat a lot of the system RAM during my entire run and don’t get in my way”.

    • Maxim Masiutin:

      We have found out that, for a GUI application written in Delphi for Win32/Win64 or written in a similar way that uses large and heavy libraries on top of the Win32 API (GDI, etc), it is worth calling SetProcessWorkingSetSize once.

      We call it with -1, -1 parameters, within a fraction of second after the application has fully opened and showed the main window to the user. In this case, the SetProcessWorkingSetSize(... -1, -1) releases lots of startup code that seem to not needed any more.

  • [WayBack] c# – How to set MinWorkingSet and MaxWorkingSet in a 64-bit .NET process? – Stack Overflow answer by Hans Passant:

    Don’t pinvoke this, just use the Process.CurrentProcess.MinWorkingSet property directly.

    Very high odds that this won’t make any difference. Soft paging faults are entirely normal and resolved very quickly if the machine has enough RAM. Takes ~0.7 microseconds on my laptop. You can’t avoid them, it is the behavior of a demand_paged virtual memory operating system like Windows. Very cheap, as long as there is a free page readily available.

    But if it “blips” you program performance then you need to consider the likelihood that it isn’t readily available and triggered a hard page fault in another process. The paging fault does get expensive if the RAM page must be stolen from another process, its content has to be stored in the paging file and has to be reset back to zero first. That can add up quickly, hundreds of microseconds isn’t unusual.

    The basic law of “there is no free lunch”, you need to run less processes or buy more RAM. With the latter option the sane choice, 8 gigabytes sets you back about 75 bucks today. Complete steal.

  • [WayBack] c++ – SetProcessWorkingSetSize usage – Stack Overflow answer by MSalters:

    I had an application which by default would close down entirely but keep listening for certain events. However, most of my code at that point would not be needed for a long time. To reduce the impact my process made, I called SetProcessWorkingSetSize(-1,-1);. This meant Windows could take back the physical RAM and give it to other apps. I’d get my RAM back when events did arrive.

    That’s of course unrelated to your situation, and I don’t think you’d benefit.

  • [WayBack] delphi – When to call SetProcessWorkingSetSize? (Convincing the memory manager to release the memory) – Stack Overflow

    If your goal is for your application to use less memory you should look elsewhere. Look for leaks, look for heap fragmentations look for optimisations and if you think FastMM is keeping you from doing so you should try to find facts to support it. If your goal is to keep your workinset size small you could try to keep your memory access local. Maybe FastMM or another memory manager could help you with it, but it is a very different problem compared to using to much memory.

    you can check the FasttMM memory usage via FasttMM calls GetMemoryManagerState and GetMemoryManagerUsageSummary before and after calling API SetProcessWorkingSetSize.

    I don’t need to use SetProcessWorkingSetSize. FastMM will eventually release the RAM.

    To confirm that this behavior is generated by FastMM (as suggested by Barry Kelly) I crated a second program that allocated A LOT of RAM. As soon as Windows ran out of RAM, my program memory utilization returned to its original value.

  • [WayBack] delphi – SetProcessWorkingSetSize – What’s the catch? – Stack Overflow answer by Rob Kennedy:

    Yes, it’s a bad thing. You’re telling the OS that you know more about memory management than it does, which probably isn’t true. You’re telling to to page all your inactive memory to disk. It obeys. The moment you touch any of that memory again, the OS has to page it back into RAM. You’re forcing disk I/O that you don’t actually know you need.

    If the OS needs more free RAM, it can figure out which memory hasn’t been used lately and page it out. That might be from your program, or it might be from some other program. But if the OS doesn’t need more free RAM, then you’ve just forced a bunch of disk I/O that nobody asked for.

    If you have memory that you know you don’t need anymore, free it. Don’t just page it to disk. If you have memory that the OS thinks you don’t need, it will page it for you automatically as the need arises.

    Also, it’s usually unwise to call Application.ProcessMessages unless you know there are messages that your main thread needs to process that it wouldn’t otherwise process by itself. The application automatically processes messages when there’s nothing else to do, so if you have nothing to do, just let the application run itself.


Posted in .NET, C, C++, Delphi, Development, Software Development, Windows Development | Leave a Comment »

Some links on thread names in Windows

Posted by jpluimers on 2021/07/01

For a very long time, it has been possible to name threads visible in debuggers: How to: Set a Thread Name in Native Code.

In the mean time, under Windows 10, you can both Get and Set the thread name. This brings native applications on par with with .NET where this has always been possible. Chrome uses these new API calls.

Which means I have some reading to do:


Posted in Debugging, Development, Software Development, Windows Development | Leave a Comment »

DCOM calls from thread pool threads: CoInitialize/CoUnitialize location and expensiveness?

Posted by jpluimers on 2021/06/24

Interesting takeaway from [WayBack] DCOM calls from thread pool threads

call CoInitialize* at the start, and call CoUninitialize before returning. Expensive, but necessary



Posted in .NET, C, C++, COM/DCOM/COM+, Delphi, Development, Software Development, Windows Development | Leave a Comment »

File Line Count: “built-in” line count for Windows

Posted by jpluimers on 2021/06/22

Windows if full of undocumented gizmo’s, like find alternative for wc -l counting all lines in a file: [WayBack] File Line Count

Use FIND command to count file lines, store line count into a variable.

Description: Running the FIND command with option /v and empty search string will find all lines
Running the FIND command with option /c will output the line count only.
The FOR command with option /f will parse the output, the line count in this case, and the set command put the line number into the cnt variable.
set file=textfile.txt
set /a cnt=0
for /f %%a in ('type "%file%"^|find "" /v /c') do set /a cnt=%%a
echo %file% has %cnt% lines
Script Output:
 DOS Script Output
textfile.txt has 50 lines

[WayBack] Stupid command-line trick: Counting the number of lines in stdin | The Old New Thing

Windows doesn’t come with wc,
but there’s a sneaky way to count the number of lines anyway:

some-command-that-generates-output | find /c /v ""

It is a special quirk of the find command
that the null string is treated as never matching.
The /v flag reverses the sense of the test,
so now it matches everything.
And the /c flag returns the count.

The reason dates back to the original MS-DOS
version of find.exe,
which according to the comments appears to have been written
in 1982.
And back then, pretty much all of MS-DOS was written in assembly

Via: batch file line count – Google Search and [WayBack] windows – How to count no of lines in text file and store the value into a variable using batch script? – Stack Overflow


Posted in Batch-Files, Development, Scripting, Software Development, Windows Development | Leave a Comment »

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