In computing, memory refers to the state information of a computing system, as it is kept active in some physical structure.

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Memory usage caused by MySQL or Apache?

Here is a screenshot of my usage today on an idle unfinished cms drupal site with a maximum of 14 added modules besides core and no activity or users. As you can see I am at my limit which is crazy ...
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285 views

is free command displaying all physical memory or there is some RAM reserved and hidden?

I am supposed to have 512MB of ram on my VM, however I see 495mb of total ram when I do free command. I would like to know if in case my system really had "precisely" 512MB of physical ram, if in ...
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158 views

What's using all of the memory in my VM? It's not the disk cache

I have an issue where when I try to build a really large project, my machine starts swapping (several GB) even though there's plenty of memory (14 GB in fact). When I run free, it shows that it's not ...
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191 views

“/sbin/yast: fork: Cannot allocate memory” on openSUSE 10.1

I guess I'll come across as a total newbie for asking this, but I get the above message right after starting an ssh session. The reason I opened the ssh session was that I came across a 500 internal ...
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2answers
467 views

raspberry pi keeps killing imagemagicks convert

My raspberry Pi keeps killing imagemagick's convert command when I'm resizing images, especially larger images. Is there any way I can prevent this?
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99 views

RES memory more than initial and maximum memory for java

We have a java application running on Centos 6.4 what we notice is that the RES is around 370m which is more then the allocated max that is 256m. Does this signify that we the application is leaking? ...
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3answers
1k views

Human readable system memory reading crom CLI?

On OS X, I get a nice human readable system memory reading like so: printf -v system_memory \ "$(system_profiler SPHardwareDataType \ | awk -F ': ' '/^ +Memory: /{print $2}')" ...
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1answer
651 views

Which parts of an ELF executable get loaded into memory, and where?

What I already know: An ELF executable has a number of sections, obviously the .text and .data sections get loaded into memory as these are the main parts of the program. But for a program to work, ...
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225 views

Where is the virtual memory stored on hard drive?

If a process wants to access a memory address that is not in physical memory, the OS outsources a page frame from physical memory to the hard drive for later use. Where on the hard drive is this data ...
4
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1answer
995 views

How to monitor RAM ECC errors on Ivy Bridge Xeon E3 processor in Linux?

How can I monitor if there are any errors in RAM that get corrected by ECC? The processor is an Intel Xeon (Ivy Bridge) processor, the operating system is Scientific Linux 6.3. On a previous system I ...
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3answers
315 views

Get separate used memory info from free -m comand

As a output of free -m command I got following. total used free shared buffers cached Mem: 2496 2260 236 0 5 438 -/+ ...
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1answer
147 views

What information exactly is in the access control bits of a page table?

I'm currently learning for an exam in operating systems. This includes learning some basics about page tables, which lead me to the question Why using hierarchical page tables? which mentions that ...
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Why does Linux show both more and less memory than I physically have installed?

I know about swap - this question isn't about that. In dmesg, the Linux (x86-64) kernel tells me this about how much memory I have: [ 0.000000] Memory: 3890880k/4915200k available (6073k kernel ...
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2answers
119 views

Where is the frame.h located in modern Linux implementations? (ubuntu specifically)

A book I am reading refers to an include file that shows how a stack frame looks on one's UNIX system. In particular: /usr/include/sys/frame.h I am having trouble finding the modern equivalent. ...
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1answer
95 views

application to see the cpu architecture in a figure

I remember there was an application that showed, in the console, or in a simple picture, the memory architecture of the system: what caches were shared by which processors, etc. but I can't remember ...
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2answers
3k views

How can i free up memory / manage memory on a linux box?

I am running two Ubuntu 12.04 servers (no GUI / desktop) using canonical's cloud images on Amazon EC2. One is a micro with 613MB of RAM and one is a medium with 3.75GB of RAM. I only have opscode's ...
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3answers
2k views

kswapd0 takes 99% to 100% CPU in RHEL 6.3

I have 5 systems on which I have just installed RHEL6. System configuration is CPU-i7 HDD-500 GB RAM-2 GB Swap- 4 GB I have installed the same software's and all the configuration as per old ...
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1answer
78 views

Not using specific memory regions due to errors

I have just installed some new RAM (2x1GB, 667, sticks from 2x512MB, 533, sticks) into an old system (perfectly valid), and all was working fine, until now. I have been having some issues when the ...
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Linux Kernel logical address space organisation

According to "Write Great Code" in almost all OS run time memory is organized into following regions: OS | Stack | Heap | Text | Static | Storage/BSS [In increasing address fashion] User ...
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2answers
195 views

find total ram memory and swap memory

I need to write a script to find total memory and total swap of several linux server (2000+). I have one trusted server from where I can login to all these 2000 servers without a password. When I run ...
2
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1answer
580 views

Huge page and performance improvemnt

How can using huge page improve performance? I have read that huge pages improve performance by reducing TLB lookups and reducing the size of the page table. Can someone tell me how this helps with ...
6
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1answer
997 views

Tracking down “missing” memory usage in linux

On an Arch 3.6.7 x86_64 kernel I am trying to account for the memory usage of the system, which the more I look at it, the more there appears to be a hole (in the accounting of used memory, a non-hole ...
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1answer
400 views

How to solve this memory issue gracefully?

I have a standard Linux (Debian testing) laptop, with a swap partition. I do a lot of experiments with it. Some of them are really memory hungry and the way Linux behaves by default is an issue for ...
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2answers
395 views

Memory management, bias to swapping

I was having 768 MB RAM. In a general day MySQL was using 100-180 mb of RAM and MySQL was swapping 80-120 mb. I was having 50-60 mb free RAM. So I thought I should upgrade. Then I upgraded my RAM ...
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132 views

Why message queues were not being used for any application?

In my Linux machine, when i run 'ipcs' command, I have the below information listed srinivas@srinivas-G41MT-S2:~$ ipcs -a ------ Shared Memory Segments -------- key shmid owner ...
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248 views

Does Linux have ways to cache IO with memory

My server has a large amount of memory. However, the amount of IO (each of which is small) is very high. Is there a way to make a virtual drive out of portion of the memory? I realize I can also use ...
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How can I reserve a block of memory from the Linux kernel?

I have a device that needs a block of memory that is reserved solely for it, without the OS intervening. Is there any way to tell BIOS or the OS that a block of memory is reserved, and it must not ...
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1answer
242 views

Limit disk buffer usage in SLES 11SP2 to allow more efficient memory overcommit on esxi host

When running VMs on an ESXi host, you can overcommit the memory. Example: host == 20GB physical RAM The amount of RAM allocated to each VM is VM1 == 10gb VM2 == 10gb VM3 == 10gb VM4 == 10gb The ...
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1answer
55 views

How might I detect memory errors if I do not have root or physical access to a Linux system?

The background to my question is as follows. I currently rent a virtual private server from a major hosting company, which I use to run a minecraft server. I have a suspicion that there may be bad ...
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893 views

httpd memory usage very high

I host a wordpress site on my server which has 2GB mem, I have used some cache plugin, but when I type ps -eo "%C : %p : %z : %a" | sort -k5 -nr in SSH, I see the httpd memory usage is very high. ...
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2answers
2k views

What a 64 bit Linux can do that 32 bit linux can't?

I ordered a server from fdcserver. Then I realized that, unless changed, fdcserver actually provides 32 bit operating as default. I logged in using SSH, typed uname -m, and to my horror I saw that I ...
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281 views

Where does the Linux kernel reside in memory ?

From some book I have, I have in my notes that the Linux kernel resides at 0xc00000000 on 32-bit systems, and is mapped into user space for performance reasons. Is this accurate ? How can I verify ...
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Increasing kernel memory size

I have an embedded board with 512MB of RAM running Linux 2.6.29 and UBoot bootloader. But the kernel is able to utilize only 128MB of RAM. I tried changing the value of XCODE_MEMSIZE, which I think ...
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2answers
168 views

Why buffers equals to used memory?

I'm using Ubuntu 11.10, virtualized by OpenVZ. That output of free -m shows that buffers is always equal to used. total used free shared buffers cached Mem: ...
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2answers
2k views

How to place / store a file in memory on linux?

I have read somewhere that one can put a file on a linux system into memory, and loading it will be superfast. How do I do this? How do I verify the file is loaded from memory?
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2answers
210 views

Monitor single process to logfile perodicly

Based on this question, I would like to log the performance of a specific process, with a frequency of say one second, to a csv (comma separated value) log file. Something like: ...
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0answers
318 views

Are there any tools to test MTD/JFFS2 for Linux 2.4 kernels

I have some issues with a platform I support and I suspect memory problems. I wanted to check the Flash parts using some MTD JFFS2 test tools, I found a link to a bunch on this site. However they ...
2
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1answer
229 views

Concept of memory mapping in Unix like systems

Can some one explain in an easy to understand way the concept of memory mappings (achieved by mmap() system call) in Unix like systems ? When do we require this functionality ?
2
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1answer
466 views

Where is max process size specified?

I've got a RHEL4 machine with 1TB of memory and have discovered that malloc and mmap refuse to allocate any memory above 512GB. Meanwhile, I don't seem to have a problem with RHEL5 machines. I'm ...
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433 views

Restricting memory area for linux kernel

I am running ltib Linux on P1022RDK (P1022 Core) platform. I have 512 MB = 0x20000000 memory. I want my Linux kernel to use the second half of the board memory (i.e from 256 MB to 512 MB) and want the ...
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1answer
346 views

What is the difference between shared memory in early unix systems vs modern unix systems?

How could processes share memory in early versions of UNIX version modern implementations of shared memory?
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4answers
2k views

Suspend/resume single process to/from disk

On occasion, we would like to suspend memory-intensive processes on our Ubuntu and OS X servers to temporarily free up some RAM for other jobs. If all we were worried about was CPU usage, a simple ...
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2answers
542 views

RSS(resident set size) is differ when use pmap and ps command

$ pmap -x 10400 10400: ./a.out Address Kbytes RSS Dirty Mode Mapping 0000000000400000 0 0 0 r-x-- a.out 0000000000600000 0 4 4 r---- a.out ...
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free reporting huge amount of used memory [duplicate]

Possible Duplicate: real memory usage I recently got access to a machine which remains rather unoccupied. I looked up the available memory and was surprised to see that so much memory has ...
0
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1answer
800 views

glibc malloc() uses mmap() for small blocks of memory allocation?

I learned that on Linux the glibc’s malloc() uses mmap() for very big chunk of memories and brk() is used for small allocations. However that does not seem to be the case when I experiment the theory ...
2
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1answer
380 views

Memory profiling the linux kernel on an embedded device

I have an linux kernel 2.6.30 on an ARM based embedded device and I have to do some kernel memory usage profiling on the device. I am thinking of monitoring the ps output on various kernel threads ...
3
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1answer
806 views

Does free() unmap the memory of a process?

I am running a C program on Linux 2.6.16 kernel. I do not think there are memory leaks in my program however the memory consumption for the program remains stable after certain operations and does not ...
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0answers
322 views

Swap space not used

I recently installed Debian 6.0.6. Here are the machine's states: CPU - AMD XP 3000+ RAM - 1 Gig HDD - IDE 80 Gig I primarily use this machine for developing toy personal projects. When I run ...
2
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1answer
576 views

High memory (user space) and highmem (kernel space)

Each process has 2 memory area: User space (high memory) and kernel space (low memmory). In the kernel space, are the first 896 MB used for mapping kernel code (not fully 1 GB)? This means, when a ...
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2answers
567 views

RAM usage doesn't add up? (Free+used < total)

Lately I've been noticing that my monitoring script which reads from /proc/meminfo and /proc/<pid> has been showing odd readings, where several hundred MB seem to be missing. htop is showing the ...