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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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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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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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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1answer
441 views

Can I use pmap to find out Memory utilization?

I want to measure memory utilization of my Apache Server. Can I use the pmap command and pass all the process IDs of httpd and take that as total utilization? pmap PID1 PID2 .... It seems that pmap ...
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3answers
6k views

Swap usage too high?

I have a debian sid box, freshly installed about a month ago, with no desktop apps running at the moment. Any command I try to run (via ssh) makes the hard disk work very hard. The system worked ...
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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
470 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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0answers
319 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 ...
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2answers
211 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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1answer
224 views

Use all system memory in Solaris

I am doing server testing and intentionally trying to crash a virtual Solaris server by using all memory. Server has a ulimit of 15 GB (several hundred GB of total system/swap memory). Is there a ...
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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 ?
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1answer
230 views

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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1answer
467 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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1answer
998 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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2answers
543 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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36 views

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 ...
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1answer
813 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 ...
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1answer
810 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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702 views

Why does Linux purge the memory cache when it is nearly full?

Here's what the memory graph looks like on a VPS running CentOS with 512MB of RAM and nginx/php-fpm/mysqld serving (mostly static) content to a couple thousand visitors per day. (those are days on ...
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324 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 ...
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4answers
2k views

how to increase memory usage manually?

There is Solaris 10 OS on our server, and I would like to make test on this server. For this test memory usage should be high. So I wonder if there is an easy way to increase memory usage manually ?
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2answers
913 views

Find the PID of top CPU/MEM usage, save to a shell variable

Is there any way to get the PID of the top CPU/MEM usage, I need to use that in a script, top command doesn't seem to work for it.
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2answers
187 views

Total RAM used by a program with `ps`? [duplicate]

Possible Duplicate: Measuring RAM usage of a program I am trying to use ps to benchmark a program, I'm just not sure which flags to use. I would like to get the amount of RAM the program ...
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3answers
387 views

Physically break into box? (Memory & disk)

I have a VPS. I might be able to encrypt my partition but I havent tried. My VPS company I believe can reset my root password although the only SSH key I see is my own. With all my data I have it ...
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1answer
2k views

How to know maximum memory usage of a process? [duplicate]

Possible Duplicate: Measuring RAM usage of a program I have a process, which is quite short-running (about 10 minutes), but memory heavy. I want to know how much memory does the process ...
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1answer
526 views

Memory ussage for TCP or named pipe message buffers?

I have a group of programs that I was stress testing today. I drastically shot up the input load to the program and it worked at first, but I had an apparent memory leak sucking up memory. The only ...
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1answer
142 views

How to create external, filesystem, read-only entrypoint for process internal memory?

Target platform is GNU/Linux. Let's say I have: void *p I want to be create entrypoint for that internal memory in filesystem like: /tmp/my_entry_point And I'd like to be able to read that ...
5
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1answer
267 views

Virtual kernel memory layout: negative values [closed]

i'm porting drivers for omap3-board to 3.5 kernel. When I start board I see it: Memory: 256MB = 256MB total Memory: 253564k/253564k available, 8580k reserved, 3226106074K highmem Virtual kernel ...
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memtester runs faster after couple of runs

I am using this test tool : http://pyropus.ca/software/memtester/ And I noticed that first 3 iterations take 4 hours but 30 iterations take only 12 hours. I was hoping that 30 iterations will take 40 ...
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2answers
13k views

What do top's %MEM and VSZ mean?

I'm working on an embedded Linux system (128MB RAM) without any swap partition. Below is its top output: Mem: 37824K used, 88564K free, 0K shrd, 0K buff, 23468K cached CPU: 0% usr 0% sys 0% nic ...
5
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1answer
753 views

Defragging RAM / OOM failure

This question is fairly lengthy, so I'll ask the questions at the top and then go through my method of coming to the questions: Did (Busybox based) rm not execute because there wasn't enough ...
6
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2answers
1k views

An oom killer thats baffling me

I am not able to understand why would kernel issue this oom killer when I see enough memory is available: Also why are there so many kernel cache pages allocated? I say enough memory is available ...
4
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2answers
233 views

crontab, instance, memory issues+spamming

I have a cronjob that runs php5 wp-cron.php every minute to update my website. However something happened and i had 30+ instance of it (31 is marked on this one dump of ps aux). It ate up my ram, ...
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2answers
318 views

Do Solaris 10 and 11 still use slab allocation for their kernel memory allocator

If not, what do they use. Please provide a source.
2
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1answer
579 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
637 views

Tomcat does not get enough memory

i'm trying to setup a jira instance on my vServer. I've got min. 1 GB ram and max. 2 GB ram. It was runing on my friends Server with only 512 MB ram. The first error was: ...
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2answers
155 views

Critical Memory [duplicate]

Possible Duplicate: free: output format My Redhat server shows the following: free -m ============= total used free shared buffers cached Mem: ...
3
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1answer
405 views

Rationale for making user space text segment start at 0x8048000

I read somewhere that (at least since Linux v. 2.6) all user-space code is placed at load address 0x8048000 in the virtual memory address space. My own observations confirm this. I have done a cat ...
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1answer
497 views

How to make the system automatically kill some processes?

Sometimes my computer starts to behave sluggishly after running too many programs/processes simultaneously, at points almost looking crashed/frozen. Using Debian Linux, is there a way to ...
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2answers
215 views

Sudden burst in free memory

I'm experiencing some strange memory management behaviour on Squeeze with Kernel 2.6. I'm trying to get to the bottom of this with nmon. Sometimes this will freeze up the system for 30 seconds to 5 ...
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0answers
473 views

Memory mapping of the Linux kernel : how extended (4MB) and regular (4KB) paging coexist?

On x86 architecture, "Extended paging" allows page frames (physical memory) to be 4 MB instead of 4 KB. The book "Understanding the Linux Kernel, 3rd" at chapter 2 "Memory Addressing", sub-chapter ...
2
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1answer
379 views

How to get the maximum virtual set size of a unix process during its lifetime?

The time command includes a format parameter "M", which according to the time man page on Linux is used for the following: Maximum resident set size of the process during its lifetime, in Kilobytes. ...
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4answers
6k views

How to find information about the RAM using the Terminal? [duplicate]

Possible Duplicate: Can I identify my RAM without shutting down linux? I need to know it to check the compatibility... I wanna know the type/size/model, etc. Can someone help? Thanks.
2
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1answer
199 views

Compare usage of memory by window managers

I'd like to test a few window managers to see which of them takes less memory and CPU in certain time period (so is better choice for older computers). I'd like to make the tests myself (not to read a ...
0
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1answer
377 views

Smallest GUI VNC setup

I'm setting up VNC on my VPS with 768mb ram. What would be the best setup to save the most memory? Right now I tried Gnome-core with vncserver but it uses a lot of RAM. I remember having a VNC ...
4
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1answer
604 views

How can I tell what memory RAM address range is being used by uboot?

I am in uboot and was wondering, how could I tell what RAM address range is being used by uboot. uboot needs memory to run so it might be using some of the RAM. I want to avoid modifying those RAM ...
2
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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 ...
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2k views

free / top difference. Does free show virtual memory?

free -m shows me the following in my system: total used free shared buffers cached Mem: 3954 3842 111 0 248 2585 -/+ ...
10
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1answer
4k views

How can I test the RAM for data corruption on an ARM-based system?

I have an embedded device. It is ARM based, with Linux 2.6.31 and has 256 MB RAM. I wanted to get some ideas/tips on what is the most effective way to test the device RAM for data corruptions. Is ...
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2answers
782 views

Is it possible to trigger OOM-killer on forced swapping?

Is it possible to have the system preemptively swap out inactive pages (vm.swappiness), but invoke the oom-killer when the system runs out of RAM (as opposed to running out of memory) and is forced to ...