This is a common misperception: while the garbage collector does its best, it’s entirely possible for even the best programmer to fall prey to crippling memory leaks. Or it can be made a part of CI and run automatically.Inexperienced programmers often think that Java’s automatic garbage collection completely frees them from worrying about memory management. JXRay can process a heap dump in place, for example on a production machine where that dump was generated. Doesn’t need to run on a machine that has a screen attached. Extremely scalable: processes 1-4 GB heap dumps in less than a minute, and can handle dumps of up to 512GB.
![]() Out of swap space?Java.lang.OutOfMemoryError: (Native method)This error message doesn’t necessarily imply a memory leak. For example: Is the OOM appearing because the Java heap is full, or because the native heap is full? To help you answer this question, let’s analyze a few of the the possible error messages:Java.lang.OutOfMemoryError: Java heap spaceJava.lang.OutOfMemoryError: PermGen spaceJava.lang.OutOfMemoryError: Requested array size exceeds VM limitJava.lang.OutOfMemoryError: request bytes for. This sounds obvious, but the answer isn’t always so clear. Thus, an error emerges, along with a stack trace.The first step in diagnosing your OOM is to determine what the error actually means. Try as it might, the garbage collector can’t find the necessary space, and the heap can’t be expanded any further. Instead, after garbage collection, the objects are queued for finalization, which occurs later. If a class has a finalize method, then objects of that type do not have their space reclaimed at garbage collection time. ( Note: APIs called by an application could also be unintentionally holding object references.)Another potential source of these “Java heap space” OOMs arises with the use of finalizers. This is the Java language equivalent of a memory leak. I solved the problem by adjusting the JVM’s memory parameters.In other cases, and for long-lived applications in particular, the message might be an indication that we’re unintentionally holding references to objects, preventing the garbage collector from cleaning them up. After some investigation, I figured out that the culprit was an array instantiation that was demanding too much memory in this case, it wasn’t the application’s fault, but rather, the application server was relying on the default heap size, which was too small. ![]() “Requested array size exceeds VM limit”This error indicates that the application (or APIs used by that application) attempted to allocate an array that is larger than the heap size. If an application interns a large number of strings, you might need to increase the size of the permanent generation.Note: you can use the jmap -permgen command to print statistics related to the permanent generation, including information about internalized String instances. In more precise terms, the java.lang.String.intern method returns a string’s canonical representation the result is a reference to the same class instance that would be returned if that string appeared as a literal. If so, it’s returned by the intern method if not, the string is added to the pool. When the intern method is invoked, the method checks the pool to see if an equivalent string is present. The java.lang.String class maintains a pool of strings. Included in the message are the size (in bytes) of the request that failed and the reason for the memory request. However, the HotSpot VM throws this apparent exception when an allocation from the native heap failed and the native heap might be close to exhaustion. Out of swap space?”This message appears to be an OOM. In most cases, the problem is either a configuration issue or a bug that results when an application attempts to allocate a massive array. Java Thread Dump Analyzer Code Is Continuously(Native method)If you see this error message and the top frame of your stack trace is a native method, then that native method has encountered an allocation failure. For example, you might see this error if:The operating system is configured with insufficient swap space.Another process on the system is consuming all available memory resources.It’s also is possible that the application failed due to a native leak (for example, if some bit of application or library code is continuously allocating memory but fails to releasing it to the operating system). In some cases, the problem might not even be related to the application. Install vmware for mac via homebrewIf the cause of a crash is determined to be a lack of error-handling in some memory allocations, then you must hunt down the reason for said allocation failure. Depending on the circumstances, this type of issue can be difficult to locate.In some cases, the information from the fatal error log or the crash dump will be sufficient. If the return from malloc is not checked, then the application might crash when it attempts to access an invalid memory location. This occurs if you’re running native code that doesn’t check for errors returned by memory allocation functions.For example, the malloc system call returns NULL if there is no memory available. Application Crash Without OOMOccasionally, an application might crash soon after an allocation failure from the native heap. Warning: the process can be lengthy and iterative. Diagnosing LeaksIn most cases, diagnosing memory leaks requires very detailed knowledge of the application in question.
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