copy-on-write Questions
2
Solved
My understanding of copy-on-write is that "Everyone has a single, shared copy of the same data until it's written, and then a copy is made".
Is a shared copy of the same data comprised of a heap ...
Malan asked 5/5, 2016 at 10:17
2
Solved
I have read about the copy-on-write principle which occurs when a new process is being forked in Linux.
I have also read about the fact that if multiple instances of one program are running at the...
Ulmaceous asked 23/8, 2015 at 19:34
2
Solved
I was just reading a Wikipedia article on Copy-on-write (curious if there are any filesystems that support it), and was surprised by the following passage:
COW is also used outside the kernel, i...
Stonybroke asked 25/6, 2013 at 13:6
1
According to GCC 5 release changes page (https://gcc.gnu.org/gcc-5/changes.html):
A new implementation of std::string is enabled by default, using the small string optimization instead of copy-o...
Brandtr asked 5/7, 2015 at 8:39
1
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I there any way to avoid copy-on-modify for in-place modifications of matrices in R?
I am trying to copy a smaller matrix to a slice of larger matrix as follows.
library(data.table)
y <-...
Loden asked 21/6, 2015 at 19:23
1
How do I prevent the GC from provoking copy-on-write, when I fork my process ? I have recently been analyzing the garbage collector's behavior in Ruby, due to some memory issues that I encountered ...
Popgun asked 20/5, 2015 at 14:53
2
Solved
I want to know how copy-on-write happens in fork().
Assuming we have a process A that has a dynamical int array:
int *array = malloc(1000000*sizeof(int));
Elements in array are initialized to s...
Llano asked 27/11, 2014 at 0:52
1
Solved
I've been playing around with copy-on-write buffers on Linux and the following example seems to work as intended:
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#in...
Navicert asked 13/3, 2015 at 16:16
4
I noticed that in python, string object keeps only one copy. Like below code:
>>> s1='abcde'
>>> s2='abcde'
>>> s1 is s2
True
s1 and s2 point to the same object.
When...
Whiplash asked 25/2, 2015 at 5:34
2
Solved
I have classes like below
class A {
@Override
public boolean equals(Object other) { return true }
}
Class B extends A {
}
Class C extends A {
@Override
public boolean equals(Object other) { ...
Guyon asked 23/7, 2014 at 20:42
2
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I get the idea behind copy-on-write. When I fork, the heap is marked as CoW, and when any process tries to change it, a copy is made. The question is: do I have to free it in a child's process none...
Berkelium asked 24/2, 2014 at 18:11
1
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I've recently discovered that using references in PHP is generally (although not always) a bad idea from a memory management or performance point of view, because of Copy On Write and the way...
Provencher asked 23/2, 2014 at 21:10
2
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I have a class that returns large NumPy arrays. These arrays are cached within the class. I would like the returned arrays to be copy-on-write arrays. If the caller ends up just reading from the ar...
Bumbailiff asked 20/2, 2014 at 1:6
2
Solved
It's known that Qt classes use copy-on-wite when passing by value. So copy isn't done until its needed. I have seen many times passing Qt classes by const reference when only needed read-only acces...
Wold asked 12/6, 2013 at 17:20
2
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Is a shared memory/copy on write implementation for general containers (like that found in Qt's containers) superseded by C++11 move semantics and rvalue references?
Where does one fail and the ot...
Dimarco asked 18/4, 2013 at 20:8
3
Solved
PHP uses a copy-on-modification system.
Does $a = (string) $a; ($a is a already string) modify and copy anything?
Especially, this is my problem:
Parameter 1 is mixed / I want to allow to pass...
Capricorn asked 28/2, 2013 at 15:43
2
Solved
According to wikipedia (which could be wrong)
When a fork() system call is issued, a copy of all the pages corresponding to the parent process is created, loaded into a separate memory location by...
Mapes asked 11/12, 2012 at 4:26
3
Solved
How to get sparse block size and check if data is present at the given offset in sparse file in reiserfs/ext3 in Linux?
I want to use it to implement simple copy-on-write block device using FUSE.
...
Junko asked 1/4, 2010 at 20:5
5
Solved
If I have an unsynchronized java collection in a multithreaded environment, and I don't want to force readers of the collection to synchronize[1], is a solution where I synchronize the writers and ...
Alesandrini asked 15/8, 2012 at 4:5
2
Solved
If we consider a std::string implementation that uses reference counting, consider this scenario:
int main()
{
string english = "Hello";
string german = english; //refcnt = 2
string german2 = g...
Splasher asked 21/6, 2012 at 23:39
1
Solved
I am implementing cp(file copy) command using mmap().
For that I mapped the source file in MAP_PRIVATE (As I just want to read)mode and destination file in MAP_SHARED mode(As I have to writeback th...
Ferrule asked 21/6, 2012 at 6:18
2
Solved
I stumbled about a method which seems to be present in all data objects like QList, QQueue, QHash...
I even investigated so far I can see the source code of it, which is
inline void setSharable(b...
Lacustrine asked 26/3, 2010 at 21:48
2
Solved
I am programming a web API client in PHP that parses CSV data into associative arrays and I want to protect my users from data-duplication when using these arrays.
My users will never be writing t...
Keyway asked 17/6, 2012 at 21:34
1
Solved
I have a large buffer:
char *buf = malloc(1000000000); // 1GB
If I forked a new process, it would have a buf which shared memory with the parent's buf until one or the other wrote to it. Even th...
Linkboy asked 12/6, 2012 at 14:38
5
I want to implement a copy-on-write on my custom C++ String class, and I wonder how to.
I tried to implement some options, but they all turned out very inefficient.
Stealthy asked 30/10, 2009 at 10:29
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