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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Is the file table in the filesystem or in memory?

In the context of operating system control tables, does the term "file tables" refer to a data structure that is part of the filesystem, or that is in main memory (and in which case I assume it would ...
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644 views

Behavior of mmap'd memory on memory pressure

I have a large tar file (60GB) containing image files. I'm using mmap() on this entire file to read in these images, which are accessed randomly. I'm using mmap() for the following reasons: Thread ...
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Access memory via a flat file in Linux

I understand everything is a flat file in Linux. How hard is it to dump the contents of the main memory into a flat file? Does it already exist in Linux? If yes, what's the path to the file? What are ...
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gnome-keyring-daemon couldn't allocate secure memory

I run logcheck on my Debian Linux system to get alerted to unusual lines in my log files, and recently I saw the following in /var/log/messages: gnome-keyring-daemon: couldn't allocate secure memory ...
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Is there any method to mount a block of memory as a filesystem in linux?

I have a question,in linux, is there any method to mount a block of memory as a filesystem? For example, in X86 architecture, when power on, I reserve a block of memory about 8 Mbytes, and then when ...
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Difference between free -m and ps -euf

I'm not an expert on linux so I do apologize in advance for the silly question. I have a vps machine with ubuntu 10.04 and 512Mb of RAM. I'm trying to guess how much memory is available after running ...
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482 views

Does window minimizing free memory usage?

Both the undisplayed maximized window and minimized window are invisible to the end user. By undisplayed I mean an inactive maximized window covered by the active window. There is a difference ...
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Measuring RAM usage of a program

time is a brilliant command if you want to figure out how much CPU time a given command takes. I am looking for something similar that can measure the max RAM usage of the program and any children. ...
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463 views

Is there a way to kick kswapd and make it swap out pages?

Even though I have set swappiness to 100 and enabled swap, nothing is being swapped out. This is probably because I don't have high memory pressure at the moment. For testing purposes though, I want ...
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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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Disable Address space layout randomization (ASLR) for my processes

I want to run some programs in Linux where I want to disable Address Space Layout Randomization (ASLR). I know to disable it at system level, which is by setting /proc/sys/kernel/randomize_va_space to ...
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Why does my system show only 3.2 GiB of RAM when I definitely have 4.0 GiB

I have 2x2 GiB sticks of RAM installed. Running memtest86 from the grub boot menu confirms this.. memtest86 reports no errors. However every which way I check my available memory in a running ...
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274 views

What are the Implications of moving to Huge mem kernel on RHEL4

I've been asked to investigate adding extra memory (> 16gb) to a RHEL 4 server and moving to a huge mem kernel. The server is used for Oracle RAC. Is it just a case of installing the hugh mem kernel ...
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How to check for hardware errors with software methods?

How can I check for bad blocks, bad memory, etc. using only software solutions? I'm using Ubuntu 11.04.
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772 views

Limiting the Size of Apache HTTPD Memory Footprint

I have a web server running Cent OS 5 with Apache. I have over 1GB of Ram and the MaxSpareServers set to 15. This would be fine under most situations, but for some reason my httpd processes are ...
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How to limit resource usage to save CPU+RAM for a certain process?

I have a dev server on which sshd sometimes stops working because the machine runs out of RAM. Yes we are running low on memory and upgrading is not a feasible choice right now. What I want to do is ...
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real memory usage

if I understand correctly, in the following output produced by free, 3535m is the actual free memory available to applications, only 413m is used, is this correct? need some clarification on the ...
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373 views

Fedora 15 - Limited RAM Access

I have an issue with Fedora 15's available memory. The laptop it is installed on has 4GB of SDRAM, but Fedora only sees 2GB. [njozwiak@calvin xpmc6720]$ free -m total used ...
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How to find memory per core on multicore CPU?

This is required information for some MPI using app that I am working with... From its Makefile template: #insert memory per core and uncomment the following line #PREPROC= -D'MB_PER_CORE=750' ...
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Does optimizing for size reduce runtime memory usage as well as binary size?

Does optimizing for size with gcc -Os only reduce the binary size of a program, or does it reduce its runtime memory usage as well? I know what exactly the results are depend on the specific code, but ...
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627 views

Solution to get data from memory of a process

If I'm using Firefox and filling out a big form (with lots of text to write), and for some reason I accidentally press F5 and all my text in the forms is lost, I can use e.g. HxD on Windows to ...
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0answers
315 views

VMO Changes After Adding New RAM To AIX?

We have a server at a client site running AIX 5.3, which we just up the RAM to 32GB, from initially 16GB (if I'm not mistaken). This server is our Application server running J2EE applications on top ...
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Linux kernel slab usage growing on embedded system

I'm in the process of QA/debugging a project on a custom embedded linux system. The problem we're VERY tight on memory, and even a couple megs can cause issues with our software. What I'm seeing ...
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Unpredictable memory explosions

The main server at my company has recently been having a lot of downtime. For reasons that neither I nor the other admins can determine, it has random (VERY sudden) explosions in memory. It becomes ...
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1answer
825 views

CentOS 5.6 x86 64 Not seeing all my memory

So I installed CentOS 5.6 on a box at my house and it is not recognizing all my memory. I have 2gb in the machine but when you run a 'free -m' or a 'top' or a 'cat /proc/meminfo' it only shows that ...
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Tracking huge buffer usage under Linux

I have a Linux server running under Debian Lenny with 4Go of RAM. It doesn't run much, just: Postfix/spamassassin (daemon mode) Bind9 KVM (one guest - 1Go of RAM for it) Every day at exactly 3:05 ...
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What is the difference between 32-bit PAE and 64-bit kernels?

I ask this only in regards to memory addressing. I know that a PAE kernel allows the OS to access more memory than a standard 32-bit kernel, however, what are the other implications? What specific ...
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Disable random memory address generation in my programs

I'm reading "The art of exploitation" and would like to try some experiments, including reading from and writing to various memory address. I've created some simple programs and trying to overwrite ...
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261 views

Linux system calls

I want to obtain information about memory used by different users and different processes which users are running and statistics about those processes like memory consumption ,execution speed etc ...
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811 views

Linux - why is kernel.shmall so low by default?

I run DB2 on Linux where I have to allocate the vast majority of memory on the machine to shared memory segments. This page is typical of the info that I've found about shmall/shmmax: ...
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352 views

Problem on Linux NAND Root Filesystem

I'm have a JFFS2 root filesystem running on a large NAND device. Every once in a while, when I restart the computer, I get error messages about invalid ELF headers when /sbin/init or /bin/login try ...
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104 views

How can I test the system footprint of applications?

I am about to develop a piece of software and I want to ascertain the impact it has on my system. The main things I am look for are load times, memory and CPU usage and shutdown time, although I would ...
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How to detect memory type under Linux?

Which Linux utility can tell me if I have registered or unbuffered ECC memory in my server? Lshw and dmidecode do not work for me; dmidecode provides no information about registered vs. unbuffered: ...
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Memory size for kernel mmap operation

I'm interested in the way Linux mmaps files into the main memory (in my context its for executing, but I guess the mmap process is the same for writing and reading as well) and which size it uses. So ...
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4answers
381 views

Mnemonics for Unix functions?

Does anyone have any useful mnemonics for remembering the order of function parameters or the return values of Unix system calls? I am suffering from "memory leaks".
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718 views

Memory management principle used by Linux

Is memory management in the Linux Kernel done using paging or segmentation or both?
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1answer
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How to view and change kernel memory size?

How can i view the kernel's share of memory on a machine? How can I increase it? What should I consider before doing it?
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What governs the limits of shell brace expansion?

In this example I refer to the expansion of a sequence of integers, but perhaps(?) the limits would be relevant to all aspects of brace expansion.. This more general view is also of interest to me. ...
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.dtors looks writable, but attempts to write segfault

This is Ubuntu 9.04, 2.6.28-11-server, 32bit x86 $ cat test.c main() { int *dt = (int *)0x08049f18; *dt = 1; } $ readelf -S ./test ... [18] .dtors PROGBITS 08049f14 000f14 000008 ...
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Read the stack of another process?

I'm trying to read a child process's stack but with no luck. I know it is possible using ptrace, but ptrace's interface allows you to read only one word at a time, and I'm trying to scan a larger ...
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Limit memory usage for a single Linux process

I'm running pdftoppm to convert a user-provided PDF into a 300DPI image. This works great, except if the user provides an PDF with a very large page size. pdftoppm will allocate enough memory to ...
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3answers
579 views

Preloading the OOM Killer

I don't have any swap partition/file on my machine, and only 2GB of RAM. Sometimes it happens that the memory gets saturated by some process (Xorg+browser+compiler+...) and the system hangs ...
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Can I identify my RAM without shutting down linux?

I'd like to price some new RAM for our in-house VMware testing server. (It's a consumer box we use for testing our software on and running business VMs). I've forgotten what kind of RAM it has and I'd ...
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781 views

Questions on Linux kernel internals

I was reading "Linux device drivers, 3rd edition" and faced a few kernel items I don't quite understand. Hope gurus on this forum will help me out. Does the Linux kernel internally operate with ...
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How do I read from /proc/$pid/mem under Linux?

The Linux proc(5) man page tells me that /proc/$pid/mem “can be used to access the pages of a process's memory”. But a straightforward attempt to use it only gives me $ cat /proc/$$/mem ...
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4answers
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How to re-load all running applications from swap space into RAM?

If my desktop run out of memory and swaps a lot then I free or kill the application wasting my RAM. But, after that, all my desktop/applications have been swapped and are horribly slow, do you know a ...
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6answers
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Is there a tool that allows logging of memory usage?

I want to monitor memory usage of a process, and I want this data to be logged. Does such a tool exist?
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945 views

How to find out how much memory a program taking

I use htop to watch my processes, but most of services ran are multi threaded, so they are shown on several lines with a % of memory use which in some cases is the same for all, sometimes it varies ...
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What are shmpages in laymans terms?

What exactly are shmpages in the grand scheme of kernel and memory terminology. If I'm hitting a shmpages limit, what does that mean? I'm also curious if this applies to more than linux
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Is it possible to execute code in heap space?

I would like to know if i can execute a code piece sitting inside the heap space?