How many Windows handles in use is "too many"?

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I understand that the answer to this question may depend on registry settings and on the version of Windows, and perhaps on the amount of RAM if there is not enough memory. For the sake of this question, assume that the server has plenty of RAM (3+ GiB).

If an application (3rd party application in this case) leaks handles at a few hundred an hour, how many total handles can that application leak before other applications will run into troubles? By "troubles" I mean, for example, fail to start a thread, fail to open a file, and so on.

I've seen some servers (lightly loaded) run just fine with a process (usually a database process) using a few tens of thousands of handles, so the old 10000 handle limit is clearly not the issue here. (And that was a per-process limit anyway, so wouldn't affect my application which is well under that point.)

Can someone either answer the question or point me at some resources that explain about how many total handles a Windows server will allow before you effectively run out (of handles or other system resources)?

See Raymond Chen's post on this topic. The window manager enforces a limit of 10K per process, and has a total limit of 32K across the system. So if it "only" leaks 100 handles per hour, then you have a few days of uptime before it starts misbehaving.

Note that not all handles are equal. Window handles are not DB handles, for example, and may follow different rules. So this restriction might not apply, depending on what sort of handles the program is leaking. Also read this blog post.

Pushing the Limits of Windows: Handles, Any process that has more than a ten thousand handles open at any given point in time is likely either poorly designed or has a handle leak, so a� As the Windows Executive (see also here) also stores some tracking information about handles, the actual limits are 16,711,680 for 64-bit Windows 10 and 16,744,448 for 32-bit Windows 10: The Executive allocates handle tables on demand in page-sized blocks that it divides into handle table entries.

The desktop heap, which is a pool of memory where the real "stuff" the handle represents lives. It's sometimes not so much how many handles you have allocated but how much memory each object under that handle is using. You can debug the heap this way. It is a pain to install.

(this was recycled from another one of my answers)

User Objects, That is, any process can use the user object handle, provided that the the application can use the window handle to display or change the� Handles and Objects. 05/31/2018; 2 minutes to read; In this article. An object is a data structure that represents a system resource, such as a file, thread, or graphic image. An application cannot directly access object data or the system resource that an object represents.

Since those values could change with new Windows versions, you can use the SysInternals tool TestLimit / TestLimit64 to get a rough estimate. The x64 version may run for a while, especially for the memory test (it might use the hard disk (swap file) to get more virtual memory).

Get the tools from http://live.sysinternals.com/WindowsInternals/ or http://download.sysinternals.com/files/TestLimit.zip

Command line options:

-p check process limit
-t check thread limit
-h check handle limit
-u check user handle limit

Handles are killing your PC? I looked at mine and, On Windows 10, you should boot with around 60,000 handles used. This is actually pretty bad, but no biggie. But, many people are starting to� For what it's worth, 1,000 handles for a process is a lot, but it does depend on what the process does. A multi-user database server will have many, many handles. calc.exe will not.

As per this recent blog post the limit of total handles for a process in Windows 10 is hard-coded as 16*1024*1024 or 16,777,216.

As the Windows Executive (see also here) also stores some tracking information about handles, the actual limits are 16,711,680 for 64-bit Windows 10 and 16,744,448 for 32-bit Windows 10:

The Executive allocates handle tables on demand in page-sized blocks that it divides into handle table entries. That means a page, which is 4096 bytes on both x86 and x64, can store 512 entries on 32-bit Windows and 256 entries on 64-bit Windows. The Executive determines the maximum number of pages to allocate for handle entries by dividing the hard-coded maximum,16,777,216, by the number of handle entries in a page, which results on 32-bit Windows to 32,768 and on 64-bit Windows to 65,536. Because the Executive uses the first entry of each page for its own tracking information, the number of handles available to a process is actually 16,777,216 minus those numbers, which explains the results obtained by Testlimit: 16,777,216-65,536 is 16,711,680 and 16,777,216-65,536-32,768 is 16,744,448.

How many handles is too many for a process?, I'm curious how many handles is too many? And is it possible that end tasking that freed up about 10GB RAM, even if the program itself may be� For XP it's 18,000: "To use this hotfix, you must create or modify the following registry values to specify the number of NT User handles that you want to allow. The maximum number is 18,000.

According to this, 10000.

6.11. Viewing the Handles a Process Has Open, The lovely Process Explorer (and handle.exe command-line equivalent) can give you this and much more. The cool thing about Process Explorer is that it even lets � About Handles and Objects. 05/31/2018; 2 minutes to read; In this article. The system uses objects and handles to regulate access to system resources for two main reasons. First, the use of objects ensures that Microsoft can update system functionality, as long as the original object interface is maintained.

What is the number of open files limits?, On 64-bit Windows in theoretically the maximum number of handles that a process R2 max open files limit � How many Windows handles in use is "too many"? Actually, a handle is a concept outside of Windows programming and is a reference to an object or thing. There are many design books that use the term handle without referring to Windows. – Thomas Matthews Dec 17 '09 at 18:25

Handle (computing), Unsourced material may be challenged and removed. Find sources: "Handle" computing – news � newspapers � books � scholar � JSTOR (April 2014) (Learn how and when to remove this template message). In computer programming, a handle is an abstract reference to a resource that is used when Like other desktop environments, the Windows API heavily uses handles to� Because multiple windows may have the same title, you should change the current console window title to a unique title. This will help prevent the wrong window handle from being returned. Use SetConsoleTitle() to change the current console window title. Here is the process: Call GetConsoleTitle() to save the current console window title.

GDIView, Displays the list of GDI resources/handles allocated by every process. Fixed bug: On some Windows 7 systems, GDIView crashed the inspected process if the Just copy the executable file (GDIView.exe) to any folder you like and run it. than the regular mode, so it's recommended to use it only when you really need it . In real time, we face many scenarios, where an application throws multiple popups. We can easily achieve this using Windows Handles in Selenium WebDriver. We use ‘Switch To’ method which allows us to switch control from one window to other. Here is a program which handles multiple windows.

Comments
  • This seems more like a ServerFault type of question maybe.
  • @Matthew Vines: I thought about that, but decided since I ran into this problem with a program I maintain, even though a 3rd party app is the one leaking the handles, that it belonged on the programmer web site. Were I an admin trying to figure this out, SF would be more appropriate.
  • This blog post from 2011 has some good empirical advice about which processes not to worry about. E.g. lsass.exe up to 30,000 (32-bit) or 50,000 (64-bit) is OK.
  • In this article, it claims that you can reach up to 16 million handles per process. I've noticed also in windows xp that two of my processes exceeded the 10k limit. I'm confused.
  • I guess the limit changed in the meanwhile, also see the answer of Thomas Weller.
  • The debug tool is no longer relevant for Windows 7 and I assume later.
  • Those are only window object handles, and doesn't impact other types of handles (file, event, mutex, etc.)