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  • How do I swap two objects in C# (specifically Mono) without triggering GC?

    - by TenFour04
    I have two array lists. that I want to swap each frame. My question is, does the variable 'temp' need to be a member variable to avoid triggering GC, assuming this method is called on dozens of objects each frame? I'm not creating a new object, just a new reference to an object. public void LateUpdate(){ ArrayList<int> temp = previousFrameCollisions; previousFrameCollisions = currentFrameCollisions; currentFrameCollisions = temp; currentFrameCollisions.clear(); } I've been told there's no reason to make a primitive into a member variable just to avoid GC, so my best guess is that this also applies to object references.

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  • List of Commonly Used Value Types in XNA Games

    - by Michael B. McLaughlin
    Most XNA programmers are concerned about generating garbage. More specifically about allocating GC-managed memory (GC stands for “garbage collector” and is both the name of the class that provides access to the garbage collector and an acronym for the garbage collector (as a concept) itself). Two of the major target platforms for XNA (Windows Phone 7 and Xbox 360) use variants of the .NET Compact Framework. On both variants, the GC runs under various circumstances (Windows Phone 7 and Xbox 360). Of concern to XNA programmers is the fact that it runs automatically after a fixed amount of GC-managed memory has been allocated (currently 1MB on both systems). Many beginning XNA programmers are unaware of what constitutes GC-managed memory, though. So here’s a quick overview. In .NET, there are two different “types” of types: value types and reference types. Only reference types are managed by the garbage collector. Value types are not managed by the garbage collector and are instead managed in other ways that are implementation dependent. For purposes of XNA programming, the important point is that they are not managed by the GC and thus do not, by themselves, increment that internal 1 MB allocation counter. (n.b. Structs are value types. If you have a struct that has a reference type as a member, then that reference type, when instantiated, will still be allocated in the GC-managed memory and will thus count against the 1 MB allocation counter. Putting it in a struct doesn’t change the fact that it gets allocated on the GC heap, but the struct itself is created outside of the GC’s purview). Both value types and reference types use the keyword ‘new’ to allocate a new instance of them. Sometimes this keyword is hidden by a method which creates new instances for you, e.g. XmlReader.Create. But the important thing to determine is whether or not you are dealing with a value types or a reference type. If it’s a value type, you can use the ‘new’ keyword to allocate new instances of that type without incrementing the GC allocation counter (except as above where it’s a struct with a reference type in it that is allocated by the constructor, but there are no .NET Framework or XNA Framework value types that do this so it would have to be a struct you created or that was in some third-party library you were using for that to even become an issue). The following is a list of most all of value types you are likely to use in a generic XNA game: AudioCategory (used with XACT; not available on WP7) AvatarExpression (Xbox 360 only, but exposed on Windows to ease Xbox development) bool BoundingBox BoundingSphere byte char Color DateTime decimal double any enum (System.Enum itself is a class, but all enums are value types such that there are no GC allocations for enums) float GamePadButtons GamePadCapabilities GamePadDPad GamePadState GamePadThumbSticks GamePadTriggers GestureSample int IntPtr (rarely but occasionally used in XNA) KeyboardState long Matrix MouseState nullable structs (anytime you see, e.g. int? something, that ‘?’ denotes a nullable struct, also called a nullable type) Plane Point Quaternion Ray Rectangle RenderTargetBinding sbyte (though I’ve never seen it used since most people would just use a short) short TimeSpan TouchCollection TouchLocation TouchPanelCapabilities uint ulong ushort Vector2 Vector3 Vector4 VertexBufferBinding VertexElement VertexPositionColor VertexPositionColorTexture VertexPositionNormalTexture VertexPositionTexture Viewport So there you have it. That’s not quite a complete list, mind you. For example: There are various structs in the .NET framework you might make use of. I left out everything from the Microsoft.Xna.Framework.Graphics.PackedVector namespace, since everything in there ventures into the realm of advanced XNA programming anyway (n.b. every single instantiable thing in that namespace is a struct and thus a value type; there are also two interfaces but interfaces cannot be instantiated at all and thus don’t figure in to this discussion). There are so many enums you’re likely to use (PlayerIndex, SpriteSortMode, SpriteEffects, SurfaceFormat, etc.) that including them would’ve flooded the list and reduced its utility. So I went with “any enum” and trust that you can figure out what the enums are (and it’s rare to use ‘new’ with an enum anyway). That list also doesn’t include any of the pre-defined static instances of some of the classes (e.g. BlendState.AlphaBlend, BlendState.Opaque, etc.) which are already allocated such that using them doesn’t cause any new allocations and therefore doesn’t increase that 1 MB counter. That list also has a few misleading things. VertexElement, VertexPositionColor, and all the other vertex types are structs. But you’re only likely to ever use them as an array (for use with VertexBuffer or DynamicVertexBuffer), and all arrays are reference types (even arrays of value types such as VertexPositionColor[ ] or int[ ]). * So that’s it for now. The note below may be a bit confusing (it deals with how the GC works and how arrays are managed in .NET). If so, you can probably safely ignore it for now but feel free to ask any questions regardless. * Arrays of value types (where the value type doesn’t contain any reference type members) are much faster for the GC to examine than arrays of reference types, so there is a definite benefit to using arrays of value types where it makes sense. But creating arrays of value types does cause the GC’s allocation counter to increase. Indeed, allocating a large array of a value type is one of the quickest ways to increment the allocation counter since a .NET array is a sequential block of memory. An array of reference types is just a sequential block of references (typically 4 bytes each) while an array of value types is a sequential block of instances of that type. So for an array of Vector3s it would be 12 bytes each since each float is 4 bytes and there are 3 in a Vector3; for an array of VertexPositionNormalTexture structs it would typically be 32 bytes each since it has two Vector3s and a Vector2. (Note that there are a few additional bytes taken up in the creation of an array, typically 12 but sometimes 16 or possibly even more, which depend on the implementation details of the array type on the particular platform the code is running on).

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  • what can cause large discrepancy between minor GC time and total pause time?

    - by cxcg
    We have a latency-sensitive application, and are experiencing some GC-related pauses we don't fully understand. We occasionally have a minor GC that results in application pause times that are much longer than the reported GC time itself. Here is an example log snippet: 485377.257: [GC 485378.857: [ParNew: 105845K-621K(118016K), 0.0028070 secs] 136492K-31374K(1035520K), 0.0028720 secs] [Times: user=0.01 sys=0.00, real=1.61 secs] Total time for which application threads were stopped: 1.6032830 seconds The total pause time here is orders of magnitude longer than the reported GC time. These are isolated and occasional events: the immediately preceding and succeeding minor GC events do not show this large discrepancy. The process is running on a dedicated machine, with lots of free memory, 8 cores, running Red Hat Enterprise Linux ES Release 4 Update 8 with kernel 2.6.9-89.0.1EL-smp. We have observed this with (32 bit) JVM versions 1.6.0_13 and 1.6.0_18. We are running with these flags: -server -ea -Xms512m -Xmx512m -XX:+UseConcMarkSweepGC -XX:NewSize=128m -XX:MaxNewSize=128m -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCApplicationStoppedTime -XX:-TraceClassUnloading Can anybody offer some explanation as to what might be going on here, and/or some avenues for further investigation?

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  • Java heap keeps on shrinking! What is happening in this graph of heap size?

    - by chillitom
    Hi Guys, This is a screen shot of a JVM (win64, 6u17) running ActiveMQ, after every garbage collection the heap size is reducing. As the heap size reduces garbage collection gets more frequent and the heap reduces more quickly. Eventually the VM locks up as it's spending all it's time in GC. -Xms is the default and -Xmx is 2048mb. What is happening!!? How can I avoid this? http://imagebin.org/92614 n.b originally posted on serverfault.com, moved to stackoverflow.com as requested

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  • Heap Dump Root Classes

    - by Adnan Memon
    We have production system going into infinite loop of full gc and memory drops form 8 gigs to like 1 MB in just 2 minutes. After taking heap dump it tells me there an is an array of java.lang.Object ([Ljava.lang.Object) with millions of java.lang.String objects having same String taking 99% of heap. But it doesn't tell me which class is referencing to this array so that I can fix it in the code. I took the heap dump using jmap tool on JDK 6 and used JProfiler, NetBeans, SAP Memory Analyzer and IBM Memory Analyzer but none of those tell me what is causing this huge array of objects?? ... like what class is referencing to it or contains it. Do I have to take a different dump with different config in order to get that info? ... Or anything else that can help me find out the culprit class causing this ... it will help a lot.

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  • How to profile object creation in Java?

    - by gooli
    The system I work with is creating a whole lot of objects and garbage collecting them all the time which results in a very steeply jagged graph of heap consumption. I would like to know which objects are being generated to tune the code, but I can't figure out a way to dump the heap at the moment the garbage collection starts. When I tried to initiate dumpHeap via JConsole manually at random times, I always got results after GC finished its run, and didn't get any useful data. Any notes on how to track down excessive temporary object creation are welcome.

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  • Java: How do you really force a GC using JVMTI's ForceGargabeCollection?

    - by WizardOfOdds
    I'm not looking for the usual "you can only hint the GC in Java using System.gc()" answers, this is not at all what this question is about. My questions is not subjective and is based on a reality: GC can be forced in Java for a fact. A lot of programs that we use daily do it: IntelliJ IDEA, NetBeans, VisualVM. They all can force GC to happen. How is it done? I take it they're all using JVMTI and more specifically the ForceGarbabeCollection (notice the "Force") but how can I try it for myself? http://java.sun.com/javase/6/docs/platform/jvmti/jvmti.html#ForceGarbageCollection Also note that this question is not about "why" I'd want to do this: the "why" may be "curiosity" or "we're writing a program similar to VisualVM", etc. The question is really "how do you force a GC using JVMTI's ForceGarbageCollection"? Does the JVM needs to be launched with any special parameters? Is any JNI required? If so, what code exactly? Does it only work on Sun VMs? Any complete and compilable example would be most welcome.

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  • Why is it a bad practice to call System.gc?

    - by zneak
    After answering to a question about how to force-free objects in Java (the guy was clearing a 1.5GB HashMap) with System.gc(), I've been told it's a bad practice to call System.gc() manually, but the comments seemed mitigated about it. So much that no one dared to upvote it, nor downvote it. I've been told there it's a bad practice, but then I've also been told garbage collector runs don't systematically stop the world anymore, and that it could also be only seen as a hint, so I'm kind of at loss. I do understand that usually the JVM knows better than you when it needs to reclaim memory. I also understand that worrying about a few kilobytes of data is silly. And I also understand that even megabytes of data isn't what it was a few years back. But still, 1.5 gigabyte? And you know there's like 1.5 GB of data hanging around in memory; it's not like it's a shot in the dark. Is System.gc() systematically bad, or is there some point at which it becomes okay? So the question is actually double: Why is it or not a bad practice to call System.gc()? Is it really a hint under certain implementations, or is it always a full collection cycle? Are there really garbage collector implementations that can do their work without stopping the world? Please shed some light over the various assertions people have made. Where's the threshold? Is it never a good idea to call System.gc(), or are there times when it's acceptable? If any, what are those times?

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  • Can I detect whether an object has called GC.SuppressFinalize?

    - by Joe White
    Is there a way to detect whether or not an object has called GC.SuppressFinalize? I have an object that looks something like this (full-blown Dispose pattern elided for clarity): public class ResourceWrapper { private readonly bool _ownsResource; private readonly UnmanagedResource _resource; public ResourceWrapper(UnmanagedResource resource, bool ownsResource) { _resource = resource; _ownsResource = ownsResource; if (!ownsResource) GC.SuppressFinalize(this); } ~ResourceWrapper() { if (_ownsResource) // clean up the unmanaged resource } } If the ownsResource constructor parameter is false, then the finalizer will have nothing to do -- so it seems reasonable (if a bit quirky) to call GC.SuppressFinalize right from the constructor. However, because this behavior is quirky, I'm very tempted to note it in an XML doc comment... and if I'm tempted to comment it, then I ought to write a unit test for it. But while System.GC has methods to set an object's finalizability (SuppressFinalize, ReRegisterForFinalize), I don't see any methods to get an object's finalizability. Is there any way to query whether GC.SuppressFinalize has been called on a given instance, short of buying Typemock or writing my own CLR host?

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  • If you stick to standard coding in .NET, is there reason to manually invoke the GC or run finalizers

    - by Matt
    If you stick to managed code and standard coding (nothing that does unconventional things withe CLR) in .NET, is there any reason to manually invoke the GC or request to run finalizers on unreferenced objects? The reason I ask is thaty I have an app that grows huge in Working Memory set. I'm wondering if calling System.GC.Collect(); and System.GC.RunFinalizers(); would help, and if it would force anything that wouldn't be done by the CLR normally anyways.

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  • ???????·?????????????????·??????·???????????WebLogic?????

    - by ???01
    Java EE??????????·????????????????????????????·??????·??????????????WebLogic Server???????????????????????????????????????·???????????????????????????????????·???????????????????????????????????????WebLogic Server????????? ????????????????????????2??????????(???)? ????????·?????????????????????????????? ???????????IT?????????????????/?????????????????????????????/??????????IT??????????????????????????????·??????????????????? ????????/???????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·?????????????????????????????? ?????????????????????????????????Oracle WebLogic Server???????????????????Java EE????????Java EE?????????????????????????????????????·??????·????????????????????????????????????????????????????????????????Java EE??????·???????????????????WebLogic Server?????Oracle Tuxedo???Oracle Coherence??????????????????????????????????????????·???????????????????????? ???????WebLogic Server???????????????????????????????????? ????????·?????????????????????????????????????(??·??????)??????????????????????????? ???·??????????????????????????? ???·????????????????????·????????WebLogic Server???????????1????????????????????????????????????????WebLogic Server???????????????????????????????????????? ???????????????2????????1???????????????????????????????????1?????????????????????????????? ???????????????????·???????????????? WebLogic Server??????????·?????????Java?????(JVM:Java Virtual Machine)????????????????????????????????????????????????????·???????????????????????????????????WebLogic Server??????????JVM????·??????????·??????(GC)???????????????????????????????? ?????????????????????????????????????·??????????????????????WebLogic Server????????1????????????????·?????????Web???????????????????????HTTP?????????????????????????????????????????????????????·????????????????????????????????????????????????????????????????????????????????? ???WebLogic Server?????????????????????????·?????????????????Web???????????URL?????????????????????????????HTTP??????????????WebLogic Server?????????????????????????????????????HTTP?????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????????????????????Web?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·????????????????·??????????????????????????????????????????????????????????????????????????? ???????????????? ???????????????????????/?????????????????????????????????????? ???????1??????·??????????????????????·??????????????Java???????????????·?????????????????????????????????????????????????????????????????????????·?????????????????????????????????????????·??????????????????????1???????? WebLogic Server?????????·????????????????????????????????????????????????????????????????????????(??)??????????????????????????????·????????????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????WebLogic Server???????????????????????????????????????????????????? ???????·?????????JVM??????????????????????????????????WebLogic Server????JVM?JRockit???????????????????????????????????????·???????????????????????GC??????????????????????????????????????????????????????????????????????? ????????????????????? ?????·??????·???????????????????WebLogic Server???????????????????????????????????·??????????????????SpecjEnterprise2010??????????????????????? WebLogic Server?????????????????JVM?JRockit????????????????????????????JVM?????????????SPECjbb2005??????????????????????JRockit???????????? ???JVM???????????Java???????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit??????????????????·????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit?????????????????????????????????????????????????????? JRockit????????????????????????????????????????????JIT(Just In-Time)?????????????????????????????·?????????????????? ??????????????????????GC??????????????????????????????GC?????????JRockit?????????????????????????GC????????????????????????????????????????GC????????????????????????????????????GC?????????????????????????1?????????JRockit?GC???????????????????????????????????????????? ?????JRockit????Sun JVM????????JVM?????????????????????????Sun JVM?????????·??????????????????????????????????????????????????????JIT?????????????????????????·????????????????????????·?????????????????????????????????JVM???????1????? ???JVM Oracle JRockit??? ???? ···???JVM?Oracle JRockit??????????????????????????JRockit Flight Recorder????????????????? ?????45???????????????????????????????????? ?WMV?? ?MP4?? ?????????·???????????????????????????????·???/JVM????????????????????????????????WebLogic Server????????????????????????????????????????????????????????????????·??????·????????????WebLogic Server??????????????????????????????????????????????????????????????????????????????????

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  • ???????·?????????????????·??????·???????????WebLogic?????|WebLogic Channel|??????

    - by ???02
    Java EE??????????·????????????????????????????·??????·??????????????WebLogic Server???????????????????????????????????????·???????????????????????????????????·???????????????????????????????????????WebLogic Server????????? ????????????????????????2??????????(???)?????????·?????????????????????????????????????????IT?????????????????/?????????????????????????????/??????????IT??????????????????????????????·??????????????????? ????????/???????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·?????????????????????????????? ?????????????????????????????????Oracle WebLogic Server???????????????????Java EE????????Java EE?????????????????????????????????????·??????·????????????????????????????????????????????????????????????????Java EE??????·???????????????????WebLogic Server?????Oracle Tuxedo???Oracle Coherence??????????????????????????????????????????·???????????????????????????????WebLogic Server???????????????????????????????????? ????????·?????????????????????????????????????(??·??????)??????????????????????????????·???????――?????????????????????·????????????????????·????????WebLogic Server???????????1????????????????????????????????????????WebLogic Server???????????????????????????????????????? ???????????????2????????1???????????????????????????????????1?????????????????????????????????????????????????·????????????????WebLogic Server??????????·?????????Java?????(JVM:Java Virtual Machine)????????????????????????????????????????????????????·???????????????????????????????????WebLogic Server??????????JVM????·??????????·??????(GC)?????????????????????????????????????????????????????????????????????·??????????????????????WebLogic Server????????1????????????????·?????????Web???????????????????????HTTP?????????????????????????????????????????????????????·????????????????????????????????????????????????????????????????????????????????? ???WebLogic Server?????????????????????????·?????????????????Web???????????URL?????????????????????????????HTTP??????????????WebLogic Server?????????????????????????????????????HTTP???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????Web?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????/?????????????????????????????????????? ???????1??????·??????????????????????·??????????????Java???????????????·?????????????????????????????????????????????????????????????????????????·?????????????????????????????????????????·??????????????????????1???????? WebLogic Server?????????·????????????????????????????????????????????????????????????????????????(??)??????????????????????????????·????????????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????WebLogic Server???????????????????????????????????????????????????????????·?????????JVM??????????????????????????????????WebLogic Server????JVM?JRockit???????????????????????????????????????·???????????????????????GC?????????????????????????????????????????????????????????????????????????????????????????????????·??????·???????????????????WebLogic Server???????????????????????????????????·??????????????????SpecjEnterprise2010???????????????????????WebLogic Server?????????????????JVM?JRockit????????????????????????????JVM?????????????SPECjbb2005??????????????????????JRockit???????????????JVM???????????Java???????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit??????????????????·????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit?????????????????????????????????????????????????????? JRockit????????????????????????????????????????????????JIT(Just In-Time)?????????????????????????????·?????????????????? ??????????????????????GC??????????????????????????????GC?????????JRockit?????????????????????????GC????????????????????????????????????????GC????????????????????????????????????GC?????????????????????????1?????????JRockit?GC?????????????????????????????????????????????????JRockit????Sun JVM????????JVM?????????????????????????Sun JVM?????????·??????????????????????????????????????????????????????JIT?????????????????????????·????????????????????????·?????????????????????????????????JVM???????1????????JVM Oracle JRockit??? ???? ···???JVM?Oracle JRockit??????????????????????????JRockit Flight Recorder????????????????? ?????45???????????????????????????????????? ?WMV?? ?MP4???????????·???????????????????????????????·???/JVM????????????????????????????????WebLogic Server????????????????????????????????????????????????????????????????·??????·????????????WebLogic Server??????????????????????????????????????????????????????????????????????????????????

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  • How common are circular references? Would reference-counting GC work just fine?

    - by user9521
    How common are circular references? The less common they are, the fewer hard cases you have if you are writing in a language with only reference counting-GC. Are there any cases where it wouldn't work well to make one of the references a "weak" reference so that reference counting still works? It seems like you should be able to have a language only use reference counting and weak references and have things work just fine most of the time, with the goal of efficiency. You could also have tools to help you detect memory leaks caused by circular references. Thoughts, anyone? It seems that Python uses references counting (I don't know if it uses a tracing collector occasionally or not for sure) and I know that Vala uses reference counting with weak references; I know that it's been done before, but how well would it work?

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  • In WPF: Children.Remove or Children.Clear doesn't free objects

    - by Bart Roozendaal
    I create some UIElements from code behind and was anticipating the garbage collection to clear up stuff. However, the objects are not free-ed at the time I expected it. I was expecting them to be freeed at RemoveAt(0), but they are only freed at the end of the program. How can I make the objects be freed when removed from the Children collection of the Canvas? <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300" MouseDown="Window_MouseDown"> <Grid> <Canvas x:Name="main" /> </Grid> </Window> The code behind is: public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } private void Window_MouseDown(object sender, MouseButtonEventArgs e) { if (main.Children.Count == 0) main.Children.Add(new MyControl() { Background = Brushes.Yellow, Width = 100, Height = 50 }); else main.Children.RemoveAt(0); } } public class MyControl : UserControl { ~MyControl() { Debug.WriteLine("Goodbye"); } }

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  • gcServer config not taking effect

    - by G33kKahuna
    I'm supporting a ASP.NET v2.0 app installed on a Windows 2003 SP3 Enterprise on a quad core 8G machine running on .NET 2.0 SP1. before enabling the config, ran "tasklist /m mscorwks.dll" Image Name PID Modules w3wp.exe 7888 mscorwks.dll add under section in web.config ran IISRESET, rebooted server too ran "tasklist /m mscorsvr.dll" INFO: No tasks are running which match the specified criteria. ran "tasklist /m mscorwks.dll" Image Name PID Modules w3wp.exe 6251 mscorwks.dll It seems like gcServer is not taking effect. Are there any additional settings/ configurations necessary to get it working?

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  • What are pinned objects?

    - by sagie
    Hi. I am trying to find a memory leak using ants memory profiler, and I've encountered in a new term: Pinned objects. Can some one give me a good & simple explanation about what this objects are, How can I pinn/Unpinn objects, and detect who pinned objects? Thanks

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  • Summary of the last decade of garbage collection?

    - by Ben Karel
    I've been reading through the Jones & Lin book on garbage collection, which was published in 1996. Obviously, the computing world has changed dramatically since then: multicore, out-of-order chips with large caches, and even larger main memory in desktops. The world has also more-or-less settled on the x86 and ARM microarchitectures for most consumer-facing systems. How has the field of garbage collection changed since the seminal book was published?

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  • Meaning of message "operations coalesced during safepoint"

    - by elec
    A java app runs with the following flag: -XX:+PrintSafepointStatistics, and then produces the following line on the standard output console: 2 VM operations coalesced during safepoint Anyone cares to explain what this mean ? More generally - is there a Java reference manual somewhere detailling all JVM flags, their use and, most importantly, the expected output, with relevant explanations ?

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  • Tuning garbage collections for low latency

    - by elec
    I'm looking for arguments as to how best to size the young generation (with respect to the old generation) in an environment where low latency is critical. My own testing tends to show that latency is lowest when the young generation is fairly large (eg. -XX:NewRatio <3), however I cannot reconcile this with the intuition that the larger the young generation the more time it should take to garbage collect. The application runs on linux, jdk 6 before update 14, i.e G1 not available.

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  • lua userdata c++ destructor

    - by anon
    In lua, for memory allocated with lua_newuserdata, is it possible to register a destructor, so that the destructor is called when the memory region is garbage collected by lua? Thanks!

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  • Why does reusing arrays increase performance so significantly in c#?

    - by Willem
    In my code, I perform a large number of tasks, each requiring a large array of memory to temporarily store data. I have about 500 tasks. At the beginning of each task, I allocate memory for an array : double[] tempDoubleArray = new double[M]; M is a large number depending on the precise task, typically around 2000000. Now, I do some complex calculations to fill the array, and in the end I use the array to determine the result of this task. After that, the tempDoubleArray goes out of scope. Profiling reveals that the calls to construct the arrays are time consuming. So, I decide to try and reuse the array, by making it static and reusing it. It requires some additional juggling to figure out the minimum size of the array, requiring an extra pass through all tasks, but it works. Now, the program is much faster (from 80 sec to 22 sec for execution of all tasks). double[] tempDoubleArray = staticDoubleArray; However, I'm a bit in the dark of why precisely this works so well. Id say that in the original code, when the tempDoubleArray goes out of scope, it can be collected, so allocating a new array should not be that hard right? I ask this because understanding why it works might help me figuring out other ways to achieve the same effect, and because I would like to know in what cases allocation gives performance issues.

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  • What's the purpose of GC.SuppressFinalize(this) in Dispose() method?

    - by mr.b
    I have code that looks like this: /// <summary> /// Dispose of the instance /// </summary> public void Dispose() { if (_instance != null) { _instance = null; // Call GC.SupressFinalize to take this object off the finalization // queue and prevent finalization code for this object from // executing a second time. GC.SuppressFinalize(this); } } Although there is a comment that explains purpose of that GC-related call, I still don't understand why it's there. Isn't object destined for garbage collection once all instances cease from existence (like, when used in using() block)? What's the use case scenario where this would play important role? Thanks!

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