0
votes
0answers
6 views

Get start and end of process segments C/C++ [migrated]

I need to get the start and end addresses of the following process segments: code, data, stack, environment. I understand how it is located in memory, but don't know how to get it using API calls or ...
13
votes
3answers
183 views

How to force Linux kernel to “freeze” (or nearly freeze) for a few hundred milliseconds

We are running a real-time process on a non real-time kernel (CentOS 6), and this is probably not going to change. We have a streaming video application that requires about 500 MB/s of PCIe traffic ...
1
vote
1answer
58 views

Why can't I see my file in RAM?

In nano, I created a simple text file named 'blue_pink_red_orange_green' with the following contents: red blue orange green pink I then opened the file again and did: sudo strings /dev/mem | ...
0
votes
0answers
23 views

Zone Normal range in system with 4G RAM

I have a 4GB RAM in my system. Following is my BIOS provided RAM map. [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009d7ff] usable [ 0.000000] BIOS-e820: [mem ...
1
vote
2answers
124 views

Using only 3.3GB but I have 8GB RAM even on Ubuntu 14.04 64bit

I have 2x 4GB(8GB) RAM installed on my motherboard and BIOS/UEFI can confirm it, but on Ubuntu 14.04 64bit only has 3424776kB or 3.266120911GB. uname -a returns: 3.13.0-36-generic #63-Ubuntu SMP Wed ...
1
vote
2answers
43 views

How to get a procesess's actual memory usage (including data in swap)

I'm trying to check how much memory strain a process is actually putting on the system, but ps, top and friends are almost useless for that purpose as they only report 3 statistics: RES - the ...
0
votes
0answers
6 views

How to walk the Kernel's VMA? [migrated]

I'm writing a kernel module that finds and parses the VM_EXEC pages of a process. This is doable through walking the virtual memory of the process, similar to what /proc/$PID/maps does. However, I ...
0
votes
0answers
21 views

How fast is a process reading/writting virtual memory?

So, we have top, htop, iotop, iostat, vmstat, etc, to measure many different things on Linux, but how can one measure how much MB/s a process is reading and writting to/from RAM, i.e., virtual memory? ...
4
votes
1answer
94 views

How OOM killer decides which process to kill first?

This answer explains the actions taken by the kernel when an OOM situation is encountered based on the value of sysctl vm.overcommit_memory. When overcommit_memory is set to 0 or 1, overcommit is ...
1
vote
0answers
36 views

What is being cached?

I have an embedded system with a low amount of memory. The system has allocation issues. Maybe due to fragmentation: Memory allocation issue on NOMMU? The platform is a NOMMU platform and so I suspect ...
10
votes
2answers
144 views

Reserve fixed RAM memory region as a block device ( with a given start physical address)

There have been a lot of questions about RAM Disks and I am aware of ramfs and tmpfs which allow the use of ram as a block device. However my interest is in using a fixed memory address range as a ...
2
votes
2answers
143 views

find out the memory allocated for a particular process in ubuntu

Could anyone please tell me how to find out the memory allocated for a particular process in ubuntu?
1
vote
2answers
98 views

Why does Linux only see 3832MB of my 4096MB of RAM?

I am setting up a lot of 64-bit RedHat VMs (VMware vSphere) for our development department in my company. Most of them start with 4096MB of RAM, but Linux only seems to recognize 3832MB. Can anyone ...
1
vote
1answer
131 views

Real vs Actual memory in Xymon/Hobbit

What is the difference between real and actual memory usage in xymon ?
0
votes
2answers
57 views

What are the positions in `free` called?

I am trying to compare the output of free with the output of sar -r: # sar -r 12:00:01 AM kbmemfree kbmemused %memused kbbuffers kbcached kbcommit %commit 12:10:01 AM 629756 65293976 ...
0
votes
0answers
38 views

Why does Android crash when stressed on Memory where as GNU-Linux keeps running?

I have two devices, an Android phone with an eGlibC stack running side by side with Bionic, and an old HP tower with Debian. My HP tower has 512 MB of RAM. My phone has 2GB of RAM. I run top on ...
6
votes
2answers
424 views

How does stack allocation work in Linux?

Does the OS reserve the fixed amount of valid virtual space for stack or something else? Am I able to produce a stack overflow just by using big local variables? I've wrote a small C program to test ...
4
votes
1answer
346 views

Maximum memory usable by a 32 bit RHEL 6 system

I have installed a 32 bit RHEL OS on a 64 bit system. From the wiki page of PAE: The Linux kernel includes full PAE mode support starting with version 2.3.23, with Linus Torvalds mentioning ...
0
votes
2answers
123 views

Linux memory usage?

We have 1TB of memory on a server which hosts an SAP application. When the app is running the memory usage shown in top is around 700GB. When the app is stopped the memory usage shown in top comes ...
0
votes
2answers
142 views

Is Inactive memory related to the Commited but unused?

From the Linux procfs documentation: Active: Memory that has been used more recently and usually not reclaimed unless absolutely necessary. Inactive: Memory which has been ...
0
votes
1answer
367 views

How to compute Linux slab memory leak in GNU/Linux ( proc/slabinfo ) of running process

How to compute Linux slab memory leak in GNU/Linux ( proc/slabinfo ) of running process ? I'm want to free usage is not working properly . I want to way how to check Memory Usage & Memory Leak ...
0
votes
1answer
320 views

How to figure out memory leaks? [closed]

I'm running Ubuntu 14.04 on Digitalocean to host my blog. I'm using HHVM + nginx + MySQL. Every few hours (~12h), there's no more RAM left and nginx throws an 502 error. I check the memory usage for ...
1
vote
1answer
73 views

Random application crashes in Linux

Sometimes after booting my computer, some applications fail to start: they crash. They're usually the largest ones, such as firefox, thunderbird or virtualbox. Rebooting or cleaning the cache usually ...
25
votes
2answers
2k views

Will Linux start killing my processes without asking me if memory gets short?

I was running a shell script with commands to run several memory-intensive programs (2-5 GB) back-to-back. When I went back to check on the progress of my script I was surprised to discover that some ...
8
votes
1answer
289 views

How to limit the total resources (memory) of a process and its children

There are plenty of questions and answers about constraining the resources of a single process, e.g. RLIMIT_AS can be used to constrain the maximum memory allocated by a process that can be seen as ...
4
votes
1answer
202 views

Does 'ulimit -m' not work on (modern) Linux?

This article claims that the -m flag to ulimit does nothing in modern Linux. I can find nothing else to corroborate this claim. Is it accurate? You may try to limit the memory usage of a process ...
0
votes
2answers
1k views

Debug out-of-memory with /var/log/messages

The following report is thrown in my messages log: kernel: Out of memory: Kill process 9163 (mysqld) score 511 or sacrifice child kernel: Killed process 9163, UID 27, (mysqld) total-vm:2457368kB, ...
2
votes
1answer
851 views

What would happen if the amount of free memory (vm.min_free_kbytes) was too low?

I came across the following parameter in kernel settings (in sysctl): vm.min_free_kbytes This is the amount of free memory (RAM) that's always free no matter what. In my case, I have only 1 GiB of ...
2
votes
3answers
453 views

how is page size determined in virtual address space?

Linux uses a virtual memory system where all of the addresses are virtual addresses and not physical addresses. These virtual addresses are converted into physical addresses by the processor. To ...
1
vote
1answer
83 views

32 bit OS memory limitation on NUMA systems

Running 32 bit Rhel 6.5 with kernel 2.6.32-431.el6.i686 on a server with 46 Gb RAM and NUMA support. CONFIG_X86_PAE=y Intel(R) Xeon(R) CPU E5-2660 0 @ 2.20GHz OS is not able to see more than 14GB ...
1
vote
0answers
276 views

About Linux Memory Compaction (CONFIG_COMPACTION)

I have a question regarding memory compaction on Linux. Generally compaction is triggered when system cannot satisfy a large contiguous memory allocation. This causes the compaction to run on all ...
2
votes
2answers
432 views

/proc/pid/maps addresses (and converting them)

When looking at the memory maps in /proc/pid/maps, we can see different length addresses 00400000-0042e000 r-xp 00000000 fb:01 268953 /bin/nano 0062e000-0062f000 r--p ...
2
votes
1answer
649 views

kernel: disabling /dev/kmem and /dev/mem

I understand that /dev/kmem and /dev/mem provide access to the memory (i.e. raw RAM) of the system. I am also aware, that /dev/kmem can be completely disabled in kernel and that access can be ...
5
votes
1answer
72 views

How the network packets are transferred to the memory on linux?

Is there some command or tool for monitoring network packets and how those packets are handled by the memory and than proceeded to the CPU on linux platform? Using tcpdump I can capture many apache ...
2
votes
1answer
470 views

Why is swap used when a lot of memory is still free? [duplicate]

In the below 2.6.18 Linux Kernel (Red Hat) server, there is a lot of free memory, but I see some swap is used. I always thought of swap as an overflow when memory has been depleted. Why would it ...
2
votes
0answers
66 views

Automatically memtest and then boot

Is there some way to reboot server, so it runs memtest (say, 1 or 2 passes) and then reboots back to Linux and writes report to some log? This feature in Windows Server 2012 helped me to diagnose bad ...
11
votes
3answers
748 views

On system memory… specifically the difference between `tmpfs,` `shm,` and `hugepages…`

I've been curious lately about the various Linux kernel memory based filesystems. Note: As far as I'm concerned, the questions below should be considered more or less optional when compared with a ...
1
vote
0answers
137 views

How to cause memory fragmentation on a Linux based embedded device?

Hardware ARM What am I trying to do: Answer: I am trying to create memory fragmentation on a Linux 2.6.31 based swapless embedded device. Why: Answer:I am trying to port some patches to Linux ...
16
votes
1answer
2k views

What is maximum RAM supportable by Linux?

What is the maximum supportable RAM by Linux? Assume that hardware is/supports 64-bit. Among all Linux distros. Does it go up to 16 exabytes, or is it limited like with Windows which I believe is 192 ...
3
votes
1answer
691 views

Optimised ZFS in low RAM environment feasibility?

I am currently setting up a file server and have come to the point of actually setting up the data drives. The system has 4 drives (one OS disk, 3 data disks). The OS disk is formatted as ext4 and ...
2
votes
2answers
1k views

How to remove cache device from bcache?

I believe, that once I made sure my cache device state is "clean": $ sudo cat /sys/block/bcache0/bcache/state I can just physically remove it from the machine when it is powered off or boot with ...
2
votes
2answers
1k views

How to reduce ClamAV memory usage?

I'm running a Ubuntu based web server (Apache, MySQL) on a 512MB VPS. This is more than sufficient for the website it is running (small forum). As I wanted to add some protection against viruses I ...
3
votes
3answers
696 views

Why does MemTotal in /proc/meminfo change?

I monitor value from /proc/meminfo file, namely the MemTotal: number. It changes if a ram module breaks, roughly by size of the memory module - this is obvious. I know the definition for the field ...
1
vote
1answer
696 views

What's exactly Compile time, Load time, and Execution time? [closed]

It's said, Compile time -- When it is known at compile time where the process will reside, compile time binding is used to generate the absolute code. Here I'm not sure what is the absolute code? ...
0
votes
1answer
75 views

Preventing a new instance of a program to open when calling it

My problem is with FBI (frame buffer image viewer) for Linux, but my question and any answers are perhaps applicable to more than only that program. I don't know. Anyway… While things are loading on ...
1
vote
0answers
16 views

Amount of memory transfer on a running Linux

Can I determinate the amount of RAM exchange (between the CPU and the RAM) on a running Linux system? I'm not looking for the max RAM speed (then memtest would be valid answer). I'm looking for the ...
0
votes
2answers
4k views

Memory usage on SunOS and Linux

I have some doubts with memory usage. Currently I have nagios check who measures used memory from free -m command on Linux. I added another script for memory usage from ...
-2
votes
1answer
77 views

Loading a kernel driver to a specific memory address

How can I load a kernel driver at a specific memory address? How could it be done with the following methods? commands/scripts like insmod or modprobe using C code (not sure if there may exist ...
1
vote
1answer
428 views

Worker MPM or Prefork?

I understand that there is a comparison topic between the two modules but this is different. I was contacting cPanel support in order to help me freeing up some memory usage on the VPS. They found ...
1
vote
1answer
963 views

Linux empty buffer cache command permission denied

I'm using the following commands to flush cache: # sync; echo 3 > /proc/sys/vm/drop_caches # sync; echo 2 > /proc/sys/vm/drop_caches # sync; echo 1 > /proc/sys/vm/drop_caches When I use ...