I have started programming in Go and I was wondering when new(Object) is used it allocates memory to the size of that object right? If this is the case how do I free this memory once I have finished using the object?
I ask this because in C++ when new is used on an object you can delete the object once there is no longer any need for the object to be stored.
I have been searching to see if Go does have delete or something similar to C++ but I have been unable to find anything.
Any help is much appreciated.
As you see here:
Go is fully garbage-collected and provides fundamental support for concurrent execution and communication.
So you don't have to care about memory allocation.
Go has garbage collection. This means the Go runtime checks in the background if an object or any other variable is not used anymore and if this is the case, frees the memory.
Also see the Go FAQ: Why is the syntax so different from C? - Why do garbage collection? Won't it be too expensive?
In Go, unlike in C and C++, but like in Java, memory is managed automatically by a garbage collector.
There is no delete to call.
Off-topic:
in C++ when new is used on an object you can delete the object once there is no longer any need for the object to be stored.
You must delete, otherwise you have memory leak.
Related
I have written a windows service using .NET technologies. I am using `JetBrains dotMemory' tool to understand the memory leak.
I am getting below report but as a new bee I am not sure how to read this.
System namespace is showing more survived bytes. But how do I know which code is the root cause of memory leak?
At the first your should decide which kind of memory issue you are going to find
Constantly growing memory consumption - get base snaphsot, get another after memory consumption is increased, open snapshots comparison, open new objects created after first snapshot, look at them to understand which should be collected.
Ensure that some key object doesn't leak - set your app in a state when some object should not be presented in memory (e.g. close some view), get snapshot, using filter on "Group by type" view to ensure that this object is not presented in memory.
Memory traffic - get base snapshot if needed, run action/algorithm in your app which you want to check, get snapshot. Open "Memory Traffic" view, look if it looks as you implemented or more objects then you expected were allocated during the action.
Grab this free book for other possible memory issues.
P.S. Only you as an app author can answer the question, is it a problem or it is as designed.
You should look at the survived bytes / retained bytes which will point you to the base instance or the root object of the creation. It depends on your application design and implementation to decide whether the specified object in the memory should be retained or not.
If you identify the root object of the creation, you should try to separate the linkage and make the .net garbage collector to automatically collect the unwanted objects.
There is no fixed flag points to identify memory leaks.
Using ANTS Memory Profiler
Using Windbg or here
One source of memory leaks are the event handlers that are not being de-referenced.
Example:
myClass.DoSomething += Event_DoSomething
You need to make sure the resources are being clearead like below:
myClass.DoSomething -= Event_DoSomething
I am currently trying to debug a nasty memory leak in our Go code.
What I know:
where memory is going (pprof with -base flag)
why new memory is being allocated ("reconnect" feature in our code)
number of goroutines is not growing (runtime.NumGoroutine())
if I do object = nil, memory will be garbage collected (good! but now I have data races with other go-routines that are using this object)
What I don't know:
why new memory is not being garbage collected. for that I need to know who holds a reference(s) to an object.
Thank you for your time and any advice!
I can suggest two tools.
Use Go Guru, to see who pointsto or referrers to a pointer. It is integrated with the vim-go plugin I use, I did a post on that here.
Valgrind is a tool for C/C++ but found an article about using it with Go.
Your code is 404 not found.
When you put object = nil. this did not be cleared immediately however when some goroutine still holds it , the object will keep still even if gc runs.
You ask who hold the reference, goroutine who uses this val without put it to nil or the goroutine uses it in a loop will both keep the reference.
The gc() will never marked a referred reference to black, then it will never be clear
When we are using dynamically allocated memory, the usefulness of the delete command is obvious - we need to let our program know that the memory at the pointer is no longer needed and can be repurposed.
Smart pointers in C++11 (e.g. unique_ptr) have a member function seemingly used for a similar purpose: release(). I thought the point of using smart pointers was to avoid having to manually handle the release of memory. Why is the release() function provided when, in this context, it seems pointless?
(pun intended)
unique_ptr::release is not equivalent to calling delete on the managed pointer. unique_ptrs are used when you want a sole entity owning a heap-allocated object. unique_ptr::release relinquishes ownership and returns the raw pointer. There might be instances when you no longer want the unique_ptr to own the managed data and yet not destroy the object - maybe you want to call a legacy API which takes a plain pointer and assumes ownership of it. Or perhaps you want your interface receive a unique_ptr but have many shared_ptrs having access to it in the implementation. So, the implementation would release from the unique_ptr and transfer ownership to one or more shared_ptrs.
unique_ptr only automatically releases memory when it goes out of scope or is assigned a new pointer, but you might want to release the memory before that (the most obvious reason would be optimizing memory usage).
Suppose there is simple object like:
object = Object.new
As I know this creates Object in memory (RAM).
Is there a way to delete this object from RAM?
Other than hacking the underlying C code, no. Garbage collection is managed by the runtime so you don't have to worry about it. Here is a decent reference on the algorithm in Ruby 2.0.
Once you have no more references to the object in memory, the garbage collector will go to work. You should be fine.
The simple answer is, let the GC (garbage collector) do its job.
When you are ready to get rid of that reference, just do object = nil. And don't make reference to the object.
The garbage collector will eventually collect that and clear the reference.
(from ruby site)
=== Implementation from GC
------------------------------------------------------------------------------
GC.start -> nil
GC.start(full_mark: true, immediate_sweep: true) -> nil
------------------------------------------------------------------------------
Initiates garbage collection, unless manually disabled.
This method is defined with keyword arguments that default to true:
def GC.start(full_mark: true, immediate_sweep: true); end
Use full_mark: false to perform a minor GC. Use immediate_sweep: false to
defer sweeping (use lazy sweep).
Note: These keyword arguments are implementation and version dependent. They
are not guaranteed to be future-compatible, and may be ignored if the
underlying implementation does not support them.
Ruby Manages Garbage Collection Automatically
For the most part, Ruby handles garbage collection automatically. There are some edge cases, of course, but in the general case you should never have to worry about garbage collection in a typical Ruby application.
Implementation details of garbage collection vary between versions of Ruby, but it exposes very few knobs to twiddle and for most purposes you don't need them. If you find yourself under memory pressure, you may want to re-evaluate your design decisions rather than trying to manage the symptom of excess memory consumption.
Manually Trigger Garbage Collection
In general terms, Ruby marks objects for garbage collection when they go out of scope or are no longer referenced. However, some objects such as Symbols never get collected, and persist for the entire run-time of your program.
You can manually trigger garbage collection with GC#start, but can't really free blocks of memory the way you can with C programs from within Ruby. If you find yourself needing to do this, you may want to solve the underlying X/Y problem rather than trying to manage memory directly.
You can't explicitly destroy object. Ruby has automatic memory management. Objects no longer referenced from anywhere are automatically collected by the garbage collector built in the interpreter.
Good article to read on how to do allocation wisely, and a few tools you can use to fine tune.
http://merbist.com/2010/07/29/object-allocation-why-you-should-care/
Here's my situation:
I have .NET wrapper-objects in a C++/CLI layer that hold pointers to unmanaged C++ objects. I've implemented the finalizer so that it deletes the unmanaged memory pointed to by the wrapper-object on garbage-collection and sets the pointer to null.
Here's the problem:
I'm watching the finalizer for the .NET wrapper-object and it gets called twice and tries to delete the same memory twice, indicating that I have somehow created 2 .NET wrapper objects that go out-of-scope, and are garbage collected while I'm still expecting the wrapper object to be in scope (these wrapper objects are getting passed to a VB.NET application).
Here's my question:
Is there anyway for me to check the handle value so that I can confirm where the wrapper objects are getting created (copied or whatever)? Currently I'm looking at the handle values (EG - 0x0014fe80), but I see 3 different values for when the object is created, added to a collection, and deleted. So I'm not sure if the GC is just moving stuff around and this is the same object, or if I'm actually seeing 3 different objects that reference the same unmanaged memory. I would like to resolve the duplicate object copies if possible, but I understand that I will probably want to implement some sort of smart pointer so that this doesn't happen.
Thanks,
Ian
Take a look at this question
Here is an implementation of a scoped_ptr that is noncopyable and has an auto-release mechanism for unmanaged objects, by #Ben Voigt
Yeah, I ended up modifying an auto_ptr class to be a shared pointer to ensure that the unmanaged memory is only deleted once through the smart pointer finalizer. I'm assuming I did something similar to all the other implementations; I created a static dictionary in the auto_ptr template class, using the native pointer value as the key, that is checked every time the finalizer is called to update the count of each item, or delete the memory.