kandi X-RAY | garbage-collection Summary
kandi X-RAY | garbage-collection Summary
SSM-based garbage sorting and recycling platform
Top functions reviewed by kandi - BETA
- Create a cart
- Create new data
- Update password
- To center
- To download user
- Search for a user
- Convert base64 string to image
- Register a user
- Add Goods to image
- Main launcher
- Log in admin
- Convert an image URL to base64
- Login with given username and password
- To cart to cart
- To order manager
- Update Goods
- Pay an order
- To get the list of users to use
- GET request
- Gets the garbage order
- Add cart to cart
garbage-collection Key Features
garbage-collection Examples and Code Snippets
Trending Discussions on garbage-collection
I know there is a similar question has been answered in this post. However, I am still confused about whether java has the retain cycle problem as java also has the WeakReference class. So, are they serving the same purpose? What the difference between two of them?...
ANSWERAnswered 2021-Jun-14 at 16:05
Java does not have the "retain cycle problem".
This problem exists for systems that use reference counting, which the Java GC does not use.
Therefore in Java the
WeakReference class has nothing to do with those. It's simply a way to hold on to a reference to something while also not preventing it from being garbage collected
In other words, you can use it to remember an object as long as something else (strongly) references it.
This functionality is quite similar to what the
weak keyword does in Swift. However, as described above, reference cycles don't stop objects from being collected in Java, so
WeakReference is not needed in this specific case.
ANSWERAnswered 2021-May-25 at 00:28
See this page about configuring garbage collection. It provides examples of how to set and update garbage-collection policies when you use Cloud Bigtable client libraries or the cbt command-line tool.
The answer to your question is that you can view garbage collection policies of certain tables by running this cbt command:
Official doc says remove cache data using
cache.evict(), but there are no explanation about nested object. For example, let's think abount
ROOT_QUERY like below.
ANSWERAnswered 2021-May-13 at 01:24
You can use
cache.modify for nested object.
I made a boxplot using seaborn.boxplot(). The x axis ranges from -0.95 to 0.95. Because the values on the x axis are important, I would like to create a colorbar that matches these values. Using plt.colorbar(), I got the following error message 'RuntimeError: No mappable was found to use for colorbar creation. First define a mappable such as an image (with imshow) or a contour set (with contourf)'. Searching for solutions on stackoverflow, I found matplotlib colorbar not working (due to garbage collection?), Matplotlib: Creating Colorbar. I gave them a try but I'm generating more errors, suggesting that I'm not doing the right thing. Therefore, I really would appreciate if someone could help me out and teach me how to do it properly. Thank you in advance for your time and sharing knowledge....
ANSWERAnswered 2021-Mar-17 at 19:38
You can add a custom colorbar with
Taking the following code from the official documentation:...
ANSWERAnswered 2021-Mar-11 at 15:02
Yes, it is possible to have concurrent
DisposeAsync calls. It is also possible to have concurrent
Dispose calls. Technically, implementations are supposed to handle this properly, but in real-world code, it's very rare to have concurrent
DisposeAsync calls, so most implementations do not handle this correctly.
If this is a source of concern, I recommend using my Disposables library, which ensures exactly-once semantics on disposal. However, it is written from the assumption that types want to implement
IDisposable, and not both.
I am sorry to ask you this basic question but I am not able to understand the concept. I read many SO post but I could not understand. Could you please give me code example to understand.
- As said in this post
Static variables cannot be elected for garbage collection while the class is loaded. They can be collected when the respective class loader (that was responsible for loading this class) is itself collected for garbage.
I understand as per theory that Classloader cannot be collected if it has a reference but I do not understand how it is possible practically. Could you please kindly explain with a code example?
Many thanks for your help!...
ANSWERAnswered 2021-Mar-08 at 21:10
I am posting my understanding hope it helps, Background understanding: Simple way to understand this is to take an example of a Tomcat or any such application. Which is java based. Tomcat can run multiple webapps. Even if you deploy same application with different name they will be treated differently. Here these both applications will have same classes but still they are treated differently. So here comes the class loaders. So you can think in a way like Tomcat is creating a class loader for each application and loading them under it.
Reclaiming of loaders: above if Tomcat is holding reference to the loader object then the loader object will not be reclaimed. And unless loader gets garbage collected the classes loaded by it stays. So if you shutdown an application, Tomcat will ultimately drefrence it's respective loader so that gc can reclaim it an clean it including the classed loaded by it.
I need some sort of algorithm to add garbage collection to my language (which is being compiled to c) and add a free statement or some other way so that it will have no memory leaks.
Yes, I looked at Garbage collection when compiling to C, but I do not understand the answer, and was hoping to get a more detailed answer on how to do it.
EDIT: for example if the code is...
ANSWERAnswered 2021-Feb-26 at 07:32
You first need to read the garbage collection handbook.
You later need to document, in written English, the conventions and invariants of your garbage collector. Is it a generational GC? Is it multi-thread friendly? Is it precise or conservative?
The book by C.Queinnec Lisp In Small Pieces is helpful. It describes how to code various Lisp interpreters, and some Lisp to C compiler. Some chapters are related to garbage collection and their relation to generated C code.
The Dragon book (about compilation) has a chapter on GC.
A.Appel's book Compiling with Continuations is also helpful.
You then could document and probably define macros implementing your GC conventions.
malloc could be considered as a slow way of allocating garbage collected data. Read for example Appel's old paper Garbage Collection can be faster than Stack allocation (it was debated later, but it does give a good intuition). You could consider fetching large memory zones with mmap(2) and allocating inside them in some faster way. Then you won't
free individual garbage values (if you adopt a copying GC strategy, using Cheney's algorithm), but will munmap(2) a large memory zone at once. Study also the C source code of
malloc implementation inside GNU libc or musl libc.
See my Bismon project as an example of C code (open source, for Linux) with GC.
Look also inside the C code of Ocaml interpreter and compiler.
Or inside the code of some open source JVM.
The Bigloo project is a Lisp to C compiler.
Consider also using Boehm conservative garbage collector open source library.
Your GC will be operating system specific, and probably target processor specific.
The RefPerSys project (in C++, with generation of C++ code at runtime) has a GC.
At last, the valgrind utility (a tool to detect memory leaks) is open source and can be considered as containing some GC.
PS. As an introduction, read the old paper by P.Wilson Uniprocessor Garbage Collection Techniques
Recently I was asked in the interview, if the strings in C# can come to the LOH. The interviewer mentioned that there is some optimization in GC logic that splits a single massive string into several smaller ones, so this string never reaches LOH.
I didn't find the related info in MSDN articles: https://docs.microsoft.com/en-us/dotnet/standard/garbage-collection/large-object-heap and https://docs.microsoft.com/en-us/archive/msdn-magazine/2008/june/clr-inside-out-large-object-heap-uncovered
So are there any implications or optimizations in CLR regarding storing strings in LOH? Is it somehow related to string interning?...
ANSWERAnswered 2021-Feb-24 at 21:29
I think the interviewer wanted to hear about String Intern Pool also as known as LargeHeapHandleTable.
One of the mistake is to assume that interned string is located in String Intern Pool in LOH.
In reality, an interned string has a hash, which is located in LargeHeapHandleTable, and then it references to Small Object Heap(SOH) or Large Object Heap(LOH).
if an interned string more than 85kb the string will be located in LOH, in other cases it will be in 2 generation in SOH and would be stored until the application has finished.
[The example of interned string] https://i.stack.imgur.com/fD0WR.png
It is described in chapter 4 Pro .Net Memory Management by Kondrad Kokosa
I'm developping a Rails application that deals with huge amounts of data and it halts since it uses all memory of my computer due to memory leak (allocated objects that are not released).
In my application, data is organized in a hierarchical way, as a tree, where each node of level "X" contains the sum of data of level "X+1". For example if the data of level "X+1" contains the amount of people in cities, level "X" contains the amount of people in states. In this way, level "X"'s data is obtained by summing up the amount of data in level "X+1" (in this case, people).
For the sake of this question, consider a tree with four levels: country, State, City and Neighbourhoods and that each level is mapped into Activerecords tables (countries, states, cities, neighbourhoods).
Data is read from a csv file that fills the leaves of the tree, that is, the neighbourhoods table.
Afetr that, data flows from bottom (neighbourhoods) to top (countries) in the following sequence:...
ANSWERAnswered 2021-Jan-22 at 02:12
This isn't really a case of a memory leak. You're just indescrimely loading data off the table which will exhaust the available memory.
The solution is to load the data off the database in batches:
According to Fundamentals of garbage collection, all threads except the one that triggered the garbage collection are suspended during garbage collection. Since the finalizers are called during the garbage collection process, I would expect the thread to be suspended until all the finalizers are executed. Thus, I would expect the following code to just "take longer" to complete. Instead, it throws a
System.OutOfMemoryException. Could someone elaborate on why this happens?
ANSWERAnswered 2020-Nov-29 at 10:20
Okay, so I did some more research, and it turns out that the garbage collector does not call the finalizers synchronously. It does the following:
- Freezes all running threads.
- Adds items that need finalization to the finalizer queue.
- Performs garbage collection on eligible objects (objects with no finalizers or with finalizers already called.)
- Thaws the threads that it froze.
After that, the finalizer thread starts running in the background along with the rest of the application, and calls the finalizers of each object in its queue. This is where the issue I described arises. The
Person objects in the heap have their references moved into the finalization queue, but their memory is not freed up until the finalization actually happens. The finalization takes place while the application is running (and more objects are created on the heap).
The garbage collector cannot reclaim the memory until finalization is over, thus, a race condition arises between the Main Thread (creating the objects) and the GC Finalizer Thread (calling the finalizers).
I have also confirmed this behaviour by debugging the IL code and seeing the execution switch between the two threads described above.
I have also found this question on SO which describes the same behaviour.
No vulnerabilities reported
You can use garbage-collection like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the garbage-collection component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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