Pushing the Limits of Windows: Handles. Handles are data structures that represent open instances of basic operating system objects applications interact with, such as files, registry keys, synchronization primitives, and shared memory. There are two limits related to the number of handles a process can create: the maximum number of handles the system sets for a process and the amount of memory available to store the handles and the objects the application is referencing with its handles.
In most cases the limits on handles are far beyond what typical applications or a system ever use. A more common class of problems arise because the lifetime of these resources must be managed by applications and, just like for virtual memory, resource lifetime management is challenging even for the best developers. An application that fails to release unneeded resources causes a leak of the resource that can ultimately cause a limit to be hit, resulting in bizarre and difficult to diagnose behaviors for the application, other applications or the system in general.
As always, I recommend you read the previous posts because they explain some of the concepts this post references, like paged pool. Each of these subsystems defines one or more types with the Object Manager to represent the resources they expose to applications. Every release of Windows introduces new object types with Windows 7 defining a total of You can see the objects defined by running the Sysinternals Winobj utility with administrative rights and navigating to the ObjectTypes directory in the Object Manager namespace:.
When an application wants to manage one of these resources it first must call the appropriate API to create or open the resource. For instance, the CreateFile function opens or creates a file, the RegOpenKeyEx function opens a registry key, and the CreateSemaphoreEx function opens or creates a semaphore. The system can look up the object the handle refers to by indexing into the handle table to locate the corresponding handle entry, which contains a pointer to the object.
For example, if the process successfully opened a file for read access, the handle entry would look like this:. To test the number of handles a process can create, Testlimit implements the —h switch that directs it to create as many handles as possible. It does so by creating an event object with CreateEvent and then repeatedly duplicating the handle the system returns using DuplicateHandle.
By duplicating the handle, Testlimit avoids creating new events and the only resources it consumes are those for the handle table entries. Active 3 years ago. Viewed 32k times. Improve this question. CodeRider CodeRider 1, 4 4 gold badges 16 16 silver badges 34 34 bronze badges. Have you tried google. I tested this. It is not immediately obvious that the limit is not 16 or 32 or some uselessly small number.
Moreover, it is not the slightest bit "difficult to tell what is being asked here", and nor is there ambiguity, vagueness, etc. I wish people closing such questions reflected a little more on the value that questions may provide to others that they do not provide to themselves. This question asked exactly what I wanted to know, and the answers were very helpful.
How else were we supposed to know it - via ESP? Add a comment. Active Oldest Votes. There is no limit that I know of, but there are two practical limits: The virtual space for the stacks. For example in bits the virtual space of the process is 4GB, but only about 2G are available for general use. By default each thread will reserve 1MB of stack space, so the top value are threads.
If you use a bits system this limit practically dissapears. The scheduler overhead. This is not a hard limit, just your program will be slower and slower the more threads you create. If maxStackSize is not a multiple of the page size, it is rounded to the next larger multiple of the page size.
For example, if you are using the. NET Framework version 2. Apple on Monday released the second beta of iOS 7, exactly two weeks after the first iteration of the software was doled out to developers. The first version of the software only came for iPhones and iPod Touches, with Apple promising to add support for other devices as time went on. In terms of how many more of these to expect, iOS 6 had four different beta versions between its June debut and late September release last year. But nooooo, they still keep those Fisher Price icons that look like they were hashed together 15 minutes before the keynote.
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