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  • JVM CMS Garbage Collecting Issues

    - by jlintz
    I'm seeing the following symptoms on an application's GC log file with the Concurrent Mark-Sweep collector: 4031.248: [CMS-concurrent-preclean-start] 4031.250: [CMS-concurrent-preclean: 0.002/0.002 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 4031.250: [CMS-concurrent-abortable-preclean-start] CMS: abort preclean due to time 4036.346: [CMS-concurrent-abortable-preclean: 0.159/5.096 secs] [Times: user=0.00 sys=0.01, real=5.09 secs] 4036.346: [GC[YG occupancy: 55964 K (118016 K)]4036.347: [Rescan (parallel) , 0.0641200 secs]4036.411: [weak refs processing, 0.0001300 secs]4036.411: [class unloading, 0.0041590 secs]4036.415: [scrub symbol & string tables, 0.0053220 secs] [1 CMS-remark: 16015K(393216K)] 71979K(511232K), 0.0746640 secs] [Times: user=0.08 sys=0.00, real=0.08 secs] The preclean process keeps aborting continously. I've tried adjusting CMSMaxAbortablePrecleanTime to 15 seconds, from the default of 5, but that has not helped. The current JVM options are as follows... Djava.awt.headless=true -Xms512m -Xmx512m -Xmn128m -XX:MaxPermSize=128m -XX:+HeapDumpOnOutOfMemoryError -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:BiasedLockingStartupDelay=0 -XX:+DoEscapeAnalysis -XX:+UseBiasedLocking -XX:+EliminateLocks -XX:+CMSParallelRemarkEnabled -verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:+PrintHeapAtGC -Xloggc:gc.log -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenPrecleaningEnabled -XX:CMSInitiatingOccupancyFraction=50 -XX:ReservedCodeCacheSize=64m -Dnetworkaddress.cache.ttl=30 -Xss128k It appears the concurrent-abortable-preclean never gets a chance to run. I read through http://blogs.sun.com/jonthecollector/entry/did_you_know which had a suggestion of enabling CMSScavengeBeforeRemark, but the side effects of pausing did not seem ideal. Could anyone offer up any suggestions? Also I was wondering if anyone had a good reference for grokking the CMS GC logs, in particular this line: [1 CMS-remark: 16015K(393216K)] 71979K(511232K), 0.0746640 secs] Not clear on what memory regions those numbers are referring to.

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  • C# WPF application is using too much memory while GC.GetTotalMemory() is low

    - by Dmitry
    I wrote little WPF application with 2 threads - main thread is GUI thread and another thread is worker. App has one WPF form with some controls. There is a button, allowing to select directory. After selecting directory, application scans for .jpg files in that directory and checks if their thumbnails are in hashtable. if they are, it does nothing. else it's adding their full filenames to queue for worker. Worker is taking filenames from this queue, loading JPEG images (using WPF's JpegBitmapDecoder and BitmapFrame), making thumbnails of them (using WPF's TransformedBitmap) and adding them to hashtable. Everything works fine, except memory consumption by this application when making thumbnails for big images (like 5000x5000 pixels). I've added textboxes on my form to show memory consumption (GC.GetTotalMemory() and Process.GetCurrentProcess().PrivateMemorySize64) and was very surprised, cuz GC.GetTotalMemory() stays close to 1-2 Mbytes, while private memory size constantly grows, especially when loading new image (~ +100Mb per image). Even after loading all images, making thumbnails of them and freeing original images, private memory size stays at ~700-800Mbytes. My VirtualBox is limited to 512Mb of physical memory and Windows in VirtualBox starts to swap alot to handle this huge memory consumption. I guess I'm doing something wrong, but I don't know how to investigate this problem, cuz according to GC, allocated memory size is very low. Attaching code of thumbnail loader class: class ThumbnailLoader { Hashtable thumbnails; Queue<string> taskqueue; EventWaitHandle wh; Thread[] workers; bool stop; object locker; int width, height, processed, added; public ThumbnailLoader() { int workercount,i; wh = new AutoResetEvent(false); thumbnails = new Hashtable(); taskqueue = new Queue<string>(); stop = false; locker = new object(); width = height = 64; processed = added = 0; workercount = Environment.ProcessorCount; workers=new Thread[workercount]; for (i = 0; i < workercount; i++) { workers[i] = new Thread(Worker); workers[i].IsBackground = true; workers[i].Priority = ThreadPriority.Highest; workers[i].Start(); } } public void SetThumbnailSize(int twidth, int theight) { width = twidth; height = theight; if (thumbnails.Count!=0) AddTask("#resethash"); } public void GetProgress(out int Added, out int Processed) { Added = added; Processed = processed; } private void AddTask(string filename) { lock(locker) { taskqueue.Enqueue(filename); wh.Set(); added++; } } private string NextTask() { lock(locker) { if (taskqueue.Count == 0) return null; else { processed++; return taskqueue.Dequeue(); } } } public static string FileNameToHash(string s) { return FormsAuthentication.HashPasswordForStoringInConfigFile(s, "MD5"); } public bool GetThumbnail(string filename,out BitmapFrame thumbnail) { string hash; hash = FileNameToHash(filename); if (thumbnails.ContainsKey(hash)) { thumbnail=(BitmapFrame)thumbnails[hash]; return true; } AddTask(filename); thumbnail = null; return false; } private BitmapFrame LoadThumbnail(string filename) { FileStream fs; JpegBitmapDecoder bd; BitmapFrame oldbf, bf; TransformedBitmap tb; double scale, dx, dy; fs = new FileStream(filename, FileMode.Open); bd = new JpegBitmapDecoder(fs, BitmapCreateOptions.None, BitmapCacheOption.OnLoad); oldbf = bd.Frames[0]; dx = (double)oldbf.Width / width; dy = (double)oldbf.Height / height; if (dx > dy) scale = 1 / dx; else scale = 1 / dy; tb = new TransformedBitmap(oldbf, new ScaleTransform(scale, scale)); bf = BitmapFrame.Create(tb); fs.Close(); oldbf = null; bd = null; GC.Collect(); return bf; } public void Dispose() { lock(locker) { stop = true; } AddTask(null); foreach (Thread worker in workers) { worker.Join(); } wh.Close(); } private void Worker() { string curtask,hash; while (!stop) { curtask = NextTask(); if (curtask == null) wh.WaitOne(); else { if (curtask == "#resethash") thumbnails.Clear(); else { hash = FileNameToHash(curtask); try { thumbnails[hash] = LoadThumbnail(curtask); } catch { thumbnails[hash] = null; } } } } } }

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  • memory usage in C# (.NET) app is very high, until I call System.GC.Collect()

    - by Chris Gray
    I've written an app that spins a few threads each of which read several MB of memory. Each thread then connects to the Internet and uploads the data. this occurs thousands of times and each upload takes some time I'm seeing a situation where (verified with windbg/sos and !dumpheap) that the Byte[] are not getting collected automatically, causing 100/150MB of memory to be reported in task manager if I call System.GC.Collect() i'm seeing a huge drop in memory, a drop of over 100MB I dont like calling System.GC.Collect() and my PC has tons of free memory. however if anyone looks at TaskManager they're going to be concerned, thinking my app is leaking horribly. tips?

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  • Is it possible to use Boehm garbage collector only for the part of the program?

    - by bialix
    I've read article in LinuxJournal about Boehm-Demers-Weiser garbage collector library. I'm interesting to use it in my library instead of my own reference counting implementation. I have only one question: is it possible to use gc only for my shared library and still use malloc/free in the main application? I'm not quite understand how gc checks the heap so I'm worrying about performance of gc in that case and possible side effects.

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  • Analysing objects generated by a Java application in between GCs.

    - by elec
    Is there a tool which could be used to analyse the objects being created between two separate garbage collection run (= number of objects created and their type) ? Heapdumps dont really work here as they perform a GC when they're invoked (or at least that's what I observed everytime so far), and I want to see which objects are collected by the GC, not which objects are left after the GC run, if that makes sense. ...or is it possible somehow to inspect the nature and size of objects being collected by the garbage collector ?

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  • Adding Timestamp to Java's GC messages in Tomcat 6

    - by ripper234
    I turned on Java's GC log options -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintGCDetails Which print out these messages to standard output (catalina.out): 314.884: [CMS-concurrent-mark-start] 315.014: [CMS-concurrent-mark: 0.129/0.129 secs] [Times: user=0.14 sys=0.00, real=0.13 secs] 315.014: [CMS-concurrent-preclean-start] 315.016: [CMS-concurrent-preclean: 0.003/0.003 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 315.016: [CMS-concurrent-abortable-preclean-start] 332.055: [GC 332.055: [ParNew: 17128K->84K(19136K), 0.0017700 secs] 88000K->70956K(522176K) icms_dc=4 , 0.0018660 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] CMS: abort preclean due to time 352.253: [CMS-concurrent-abortable-preclean: 0.023/37.237 secs] [Times: user=0.78 sys=0.02, real=37.23 secs] How can I make these log lines appear with an actual timestamp (including date) instead of these numbers, which presumably mean "time since JVM started" ?

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  • Why does GC.GetTotalMemory() report huge memory allocations?

    - by Seventh Element
    I have been playing around with GC.GetTotalMemory(). When I create a local variable of type Titles in the example below, the consumed amount of memory increases by 6276 bytes. What's going on here? class Program { enum Titles { Mr, Ms, Mrs, Dr }; static void Main(string[] args) { GetTotalMemory(); Titles t = Titles.Dr; GetTotalMemory(); } static void GetTotalMemory() { long bytes = GC.GetTotalMemory(true); Console.WriteLine("{0}", bytes); } }

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  • JVM GC demote object to eden space?

    - by Kevin
    I'm guessing this isn't possible...but here goes. My understanding is that eden space is cheaper to collect than old gen space, especially when you start getting into very large heaps. Large heaps tend to come up with long running applications (server apps) and server apps a lot of the time want to use some kind of caches. Caches with some kind of eviction (LRU) tend to defeat some assumptions that GC makes (temporary objects die quickly). So cache evictions end up filling up old gen faster than you'd like and you end up with a more costly old gen collection. Now, it seems like this sort of thing could be avoided if java provided a way to mark a reference as about to die (delete keyword)? The difference between this and c++ is that the use is optional. And calling delete does not actually delete the object, but rather is a hint to the GC that it should demote the object back to Eden space (where it will be more easily collected). I'm guessing this feature doesn't exist, but, why not (is there a reason it's a bad idea)?

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  • A question about GC

    - by chun
    This is a quesiton taken from a java exam, How many objects are eligible for gabage collection at #1 ? public class Main { Integer x = 32768; public static void main(String[] args) { Main m = new Main(); m = null; // #1 } } I thought it just collect Integer x, does GC even collect the Main object m?

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  • Java GC: top object classes promoted (by size)?

    - by Java Geek
    Hello! Please let me know what is the best way to determine composition of young generation memory promoted to old generation, after each young GC event? Ideally I would like to know class names which are responsible say, for 80% of heap in each "young gen - old gen" promotion chunk; Example: I have 600M young gen, each tenure promotes 6M; I want to know which objects compose this 6M. Thank you.

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  • Acceptable GC frequency for a SlimDX/Windows/.NET game?

    - by Rei Miyasaka
    I understand that the Windows GC is much better than the Xbox/WP7 GC, being that it's generational and multithreaded -- so I don't need to worry quite as much about avoiding memory allocation. SlimDX even has some unavoidable functions that generate some amount of garbage (specifically, MapSubresource creates DataBoxes), yet people don't seem to be too upset about it. I'd like to use some functional paradigms to write my code too, which also means creating objects like closures and monads. I know premature optimization isn't a good thing, but are there rules of thumb or metrics that I can follow to know whether I need to cut down on allocations? Is, say, one gen 0 GC per frame too much? One thing that has me stumped is object promotions. Gen 0 GCs will supposedly finish within a millisecond or two, but if I'm understanding correctly, it's the gen 1 and 2 promotions that start to hurt. I'm not too sure how I can predict/prevent these.

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  • What is an acceptable GC frequency for a SlimDX/Windows/.NET game?

    - by Rei Miyasaka
    I understand that the Windows GC is much better than the Xbox/WP7 GC, being that it's generational and multithreaded -- so I don't need to worry quite as much about avoiding memory allocation. SlimDX even has some unavoidable functions that generate some amount of garbage (specifically, MapSubresource creates DataBoxes), yet people don't seem to be too upset about it. I'd like to use some functional paradigms to write my code too, which also means creating objects like closures and monads. I know premature optimization isn't a good thing, but are there rules of thumb or metrics that I can follow to know whether I need to cut down on allocations? Is, say, one gen 0 GC per frame too much? One thing that has me stumped is object promotions. Gen 0 GCs will supposedly finish within a millisecond or two, but if I'm understanding correctly, it's the gen 1 and 2 promotions that start to hurt. I'm not too sure how I can predict/prevent these.

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  • MODI leaking memory

    - by Khragg
    I have an app where I'm using MODI 2007 to OCR several multi-page tiff files. I have found that when I kick it off on a directory that contains several good tiffs but also some tiffs that cannot be opened in Windows Picture and Fax Viewer, then MODI also fails to OCR those "bad" tiffs. When this happens, the app is unable to reclaim any of the memory that was used by MODI to OCR those tiffs. After the tool tries to OCR too many of these "bad" tiffs, the machine runs out of memory and the app crashes. I have tried several code fixes from the web that supposedly fix any MODI memory leaks, but so far none have worked for me. I am pasting in the part of the code below that does the OCRing: StringBuilder strRecText = new StringBuilder(10000); MODI.Document doc1 = new MODI.Document(); doc1.Create(name); try { doc1.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true); // this will ocr all pages of a multi-page tiff file } catch (Exception e) { doc1.Close(false); // clean up if (doc1 != null) { GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); GC.WaitForPendingFinalizers(); System.Runtime.InteropServices.Marshal.FinalReleaseComObject(doc1); doc1 = null; } } MODI.Images images = doc1.Images; for (int imageCounter = 0; imageCounter < images.Count; imageCounter++) { if (imageCounter > 0) { if (!noPageBreakFlag) { strRecText.Append((char)pageBreakChar); } } MODI.Image image = (MODI.Image)images[imageCounter]; MODI.Layout layout = image.Layout; strRecText.Append(layout.Text); GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); GC.WaitForPendingFinalizers(); if (layout != null) { System.Runtime.InteropServices.Marshal.FinalReleaseComObject(layout); layout = null; } if (image != null) { System.Runtime.InteropServices.Marshal.FinalReleaseComObject(image); image = null; } } File.AppendAllText(ocrFile, strRecText.ToString()); // write the OCR file out to disk GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); GC.WaitForPendingFinalizers(); if (images != null) { System.Runtime.InteropServices.Marshal.FinalReleaseComObject(images); images = null; } GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); GC.WaitForPendingFinalizers(); doc1.Close(false); // clean up if (doc1 != null) { System.Runtime.InteropServices.Marshal.FinalReleaseComObject(doc1); doc1 = null; } GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); GC.WaitForPendingFinalizers();

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  • Remote application monitoring through Visual GC

    - by Poole
    I am trying to monitor an application available on remote machine using VisualVM & Visual GC. I have enabled the jmxremote on the remote side as follows: -Dcom.sun.management.jmxremote, -Dcom.sun.management.jmxremote.port=8888, -Dcom.sun.management.jmxremote.ssl=false, -Dcom.sun.management.jmxremote.authenticate=false While monitoring through VisualVM, everything runs fine but VisualGC doesn't displays any stats (getting Not Supported for this JVM error). While tried to monitor one local application, VisualGC runs fine... Got success with the remote app once started jstad on the remote jvm. Is this a known issue with VisualGC...? Remote JVM - 1.5 Local JVM - 1.6

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  • How to analyse Dalvik GC behaviour?

    - by HRJ
    I am developing an application on Android. It is a long running application that continuously processes sensor data. While running the application I see a lot of GC messages in the logcat; about one every second. This is most probably because of objects being created and immediately de-referenced in a loop. How do I find which objects are being created and released immediately? All the java heap analysis tools that I have tried(*) are bothered with the counts and sizes of objects on the heap. While they are useful, I am more interested in finding out the site where temporary short-lived objects get created the most. (*) I tried jcat and Eclipse MAT. I couldn't get hat to work on the Android heap-dumps; it complained of an unsupported dump file version.

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  • Monotouch threads, GC, WCF

    - by cvista
    Hi This is a question about best practices i guess but it applies directly to my current MT project. I'm using WCF services to communicate with the server. To do this i do the following: services.MethodToCall(params); and the asynch: services.OnMethodToCallCompleted += delegate{ //do stuff and ting }; This can lead to issues if you're not careful in that variables defined within the scope of the asynch callback can sometimes be cleaned up by the gc and this can cause crashes. So - I am making it a practice to declare these outside of the scope of the callback unless I am 100% sure they are not needed. Now - when doing stuff and ting implies changing the ui - i wrap it all in an InvokeOnMainThread call. I guess wrapping everything in this would slow the main thread down and rubbish the point of having multi threads. Even though I'm being careful about all this i am still getting crashes and I have no idea why! I am certain it has something to do with threads, scope and all that. Now - the only thing I can think of outside of updating the UI that may need to happen inside of InvokeOnMainThread is that I have a singleton 'Database' class. This is based on the version 5 code from this thread http://www.yoda.arachsys.com/csharp/singleton.html So now if the service method returns data that needs to be added/updated to the Database class -I also wrap this inside an InvokeOnMainThread call. Still getting random crashes. So... My question is this: I am new to thick client dev - I'm coming from a web dev perspective where we don't need to worry about threads so much :) Aside from what I have mentioned -are there any other things I should be aware of? Is the above stuff correct? Or am i miss-understanding something? Cheers w://

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  • Weird stuttering issues not related to GC.

    - by Smills
    I am getting some odd stuttering issues with my game even though my FPS never seems to drop below 30. About every 5 seconds my game stutters. I was originally getting stuttering every 1-2 seconds due to my garbage collection issues, but I have sorted those and will often go 15-20 seconds without a garbage collection. Despite this, my game still stutters periodically even when there is no GC listed in logcat anywhere near the stutter. Even when I take out most of my code and simply make my "physics" code the below code I get this weird slowdown issue. I feel that I am missing something or overlooking something. Shouldn't that "elapsed" code that I put in stop any variance in the speed of the main character related to changes in FPS? Any input/theories would be awesome. Physics: private void updatePhysics() { //get current time long now = System.currentTimeMillis(); //added this to see if I could speed it up, it made no difference Thread myThread = Thread.currentThread(); myThread.setPriority(Thread.MAX_PRIORITY); //work out elapsed time since last frame in seconds double elapsed = (now - mLastTime2) / 1000.0; mLastTime2 = now; //measures FPS and displays in logcat once every 30 frames fps+=1/elapsed; fpscount+=1; if (fpscount==30) { fps=fps/fpscount; Log.i("myActivity","FPS: "+fps+" Touch: "+touch); fpscount=0; } //this should make the main character (theoretically) move upwards at a steady pace mY-=100*elapsed; //increase amount I translate the draw to = main characters Y //location if the main character goes upwards if (mY<=viewY) { viewY=mY; } }

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  • Java without gc - io

    - by Dan
    Hi Guys I would like to run a Java program with garbage collection switched off. Managing memory in my own code is not so difficult. However the program needs quite a lot of I/O. Is there any way (short of using JNI for all I/O operations) that I could achieve this using pure Java? Thanks Daniel

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  • How to free virtual memory ?

    - by Mehdi Amrollahi
    I have a crawler application (with C#) that downloads pages from web . The application take more virtual memory , even i dispose every object and even use GC.Collect() . This , have 10 thread and each thread has a socket that downloads pages . I use dispose method and even use GC.Collect() in my application , but in 3 hour my application take 500 MB on virtual memory (500 MB on private bytes in Process explorer) . Then my system will be hang and i should restart my pc . Is there any way that i use to free vitual memory ? Thanks .

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  • TreeNodes don't get collected with weakevent solution

    - by Marcus
    Hi, When I use this method http://stackoverflow.com/questions/1089309/weak-events-in-net (by Egor) to hook up a event i a inherited treenode, the tree node never gets collected, is there any speciall case with tree nodes and GC? public class MyTreeNode : TreeNode { public MyTreeNode(Entity entity) { entity.Children.ListChanged += new ListChangedEventHandler(entityChildren_ListChanged).MakeWeak(eh => entity.Children.ListChanged -= eh); } } Entity.Children is a bindinglist. I made tests with a destructor on MyTreeNode and invoking GC.Collect(), with the weak eventhandler the treenode never gets collected but i DOES get collected WIHTOUT the weak eventhandler.

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  • Associating an object with another object for GC clearup

    - by thecoop
    Is there any way of associating an object instance (object A) with a second object (object B) in a generalised way, so that when B gets collected A becomes eligable for collection? The same behaviour that would happen if B had an instance variable pointing to A, but without explicitly changing the class definition of B, and being able to do this in a dynamic way? The same sort of effect could be done by using the Component.Disposed event in a funky way, but I don't want to make B disposable EDIT I'm basically creating a cache of objects that are associated with a single 'root' object, and I don't want the cache to be static, as there can be lots of root objects using different caches, so lots of memory will be used up when a root object is no longer used but the cached objects are still around. So, I want a collection of cached objects to be associated with each 'root' object, without changing the root object definition. Sort of like metadata of an extra object reference attached to each root object instance. That way, each collection will get collected when the root object is collected, and not hang around like they would if a static cache was used.

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  • Clojure closures and GC

    - by Ralph
    It is my understanding that the default ClassLoader used in Java (and thus, Clojure) holds on to pointers to any anonymous classes created, and thus, onto lambdas and closures. These are never garbage collected, and so represent a "memory leak". There is some investigation going on for Java 7 or 8 to adding an anonymous ClassLoader that will not retain references to these functions. In the mean time how are people dealing with writing long-running applications in languages like Clojure and Scala, that encourage the use of these constructs? Is there any possibility that Clojure could provide its own anonymous ClassLoader, extending the system one, but not holding onto created classes?

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