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How do you measure the memory footprint of a set of forked processes?

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http://serverfault.com – Say I've got a process using 200MB of memory, and it fork()s: python -c "import os; data='x'*200000000; os.fork(); raw_input()" Programs like 'top' will show each process using 200MB, with very little SHRd memory, so it appears as if the processes are using 400MB in total. However, because fork() implements copy-on-write (COW) for the process's memory pages, the reality is that the processes are only using 200MB in total. Why doesn't top show what fraction of the memory is COW? Is there a way to make it do so? Or is there another command I can use instead? Note: 'top' on OSX seems to ha (HowTos)

xskl's picture
Submitted by xskl on 10/19/2012

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Dear All,

I am new to this community and this is my first post. I am facing an issue where the process starts hanging. When I closely look at the logs I come to know that some of the child processes that are forked by the parent process are not finished. Regarding this I have a few questions:

i am using ubuntu 12.04LTS on my linode vps include core2 cpu, 2gb RAM. I am doing a lot of research on optimizing memory for mysql and apache process -> optimize apache memory use, there i am using two scripts for compute memory per process.

On Windows 7 and Windows 2008 SP2, how can I view who or what is using up my memory?

I just came to realize that my system is not limiting the amount of processes per user properly thus not preventing a user from dring a fork-bomb and crashing the entire system:

user@thebe:~$ cat /etc/security/limits.conf | grep user user hard nproc 512 user@thebe:~$ ulimit -u 1024 user@thebe:~$ :(){ :|:& };: [1] 2559 user@thebe:~$ ht-bash: fork: Cannot allocate memory -bash: fork

I am running apache on Fedora with mod_perl. The server forks a process to send an email frequently - and the fork exits.

Suddenly, I got: Cannot fork: Cannot allocate memory. There was plenty of free memory in the system, not too many apache processes running. Restarting the server httpd graceful resolved the issue.

What would cause something like this?

How to free PHP-FPM memory? 1 year 6 weeks ago

There are several discussions complaining high memory usage of PHP-FPM, without any practical approach to overcome. As I explored the problem with numerous tests, the problem is related to the age of PHP-FPM age.

Imagine we have pm.max_children = 10, and have a PHP script consuming 10M memory. One expects needing 100MB of MB. This is correct for the first 10 processes.

dear all,

kindly i want to check my server memory utilization i used alot of commands but i want to make sure that it is acurate let me explain

i have a server which has 32GB RAM

Total Memory = 33423360 kb Free Memory = 4172568 kb Utilized Memory = 29250792 kb Memory Utilization Percentage = 87.5 %

if Utilized Memory = 29250792 kb how can i make sure which processes eat this amount of memo

How many process will get executed for one fork method..

A process executes the code

fork(); fork(); fork();

The total number of child processes created

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 the OS for the child process. But this is not needed in certain cases.