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

learn more… | top users | synonyms

3
votes
2answers
5k views

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 ...
4
votes
1answer
1k views

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 ...
3
votes
1answer
272 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 ...
4
votes
1answer
815 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: ...
5
votes
1answer
357 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 ...
1
vote
1answer
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 ...
14
votes
3answers
4k views

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: ...
8
votes
3answers
535 views

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 ...
0
votes
4answers
391 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".
9
votes
2answers
742 views

Memory management principle used by Linux

Is memory management in the Linux Kernel done using paging or segmentation or both?
1
vote
1answer
1k views

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?
7
votes
2answers
636 views

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. ...
7
votes
2answers
2k views

.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 ...
12
votes
4answers
3k views

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 ...
45
votes
4answers
39k views

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 ...
3
votes
3answers
594 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 ...
5
votes
2answers
2k views

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 ...
3
votes
2answers
801 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 ...
61
votes
3answers
34k views

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 ...
13
votes
4answers
5k views

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 ...
9
votes
6answers
3k views

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?
8
votes
2answers
982 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 ...
4
votes
1answer
2k views

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
3
votes
2answers
1k views

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?
2
votes
2answers
241 views

How to reuse Physical memory in the absence of swapping?

How can I reuse physical memory in the absence of swapping?
5
votes
3answers
652 views

Is it possible to support multiple processes without support for Virtual memory?

Is it possible to support multiple processes without support for virtual memory? I would like to know more about it if so.
5
votes
2answers
1k views

ZONE_NORMAL and it's association with Kernel/User-pages?

Above is presented a case where I have only 512 MB of physical memory. What I have read up so far, is that ZONE_NORMAL is mapped to the kernel virtual address space as shown. Essentially I have a ...
8
votes
2answers
893 views

Kernel Panic because of RAM stick?

one of my RAM sticks causes a Kernel Panic on my Ubuntu 10.10 (something like "not syncing" with a lot of memory adresses shown on screen). It's definitely this one RAM stick and not its socket ...
11
votes
1answer
5k views

What does the Virtual kernel Memory Layout in dmesg imply?

While going through the "Output of dmesg" I could see a list of values which i am not able to understand properly. Memory: 2047804k/2086248k available (3179k kernel code, 37232k reserved, 1935k ...
26
votes
5answers
50k views

How to find which processes are taking all the memory?

I'm looking for somthing like top is to CPU usage. Is there a command line argument for top that does this? Currently, my memory is so full that even 'man top' fails with out of memory :)
10
votes
4answers
4k views

Shell command to read device registers?

On a single-board computer running Linux, is there a way to read the contents of the device configuration registers that control hardware? I think it would be a wrapper for inw(), more or less. I'm ...
54
votes
5answers
25k views

What are high memory and low memory on Linux?

I'm interested in the difference between Highmem and Lowmem: Why is there such a differentiation? What do we gain by doing so? What features does each have?
11
votes
1answer
472 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?
0
votes
2answers
2k views

How does cached memory work for executables?

I always understood cached memory in Linux (as in free -m) as pages of memory that can be reused if they are needed again, or quickly freed if more memory is needed by new applications (I found this ...
2
votes
4answers
6k views

What is “System Memory ” displayed in nmon in AIX?

I have a host with AIX 6.1 (6100-04-02-1007) upgraded from AIX 5.1 with Veritas Storage Foundation 5.1. Since the upgrade from AIX 5.3 to 6.1, Run vx services means a lots of memory consumed that I ...
4
votes
3answers
242 views

Randomise or shred memory of an application

Is it possible to randomise or shred memory of a particular application just after its life ends, or better, whenever it deallocates some memory? A command-line utility like this would be perfect: ...
2
votes
1answer
309 views

Kernel memory allocator patch

Is there any patch for Linux kernel to use different memory allocators, such as ned allocator or TLSF allocator?
16
votes
6answers
5k views

Is there a way to limit the amount of memory a particular process can use in Unix?

I need to test a process for memory management. I do not have the source, so I need to do all the testing from the OS side. I want to be able to say something like limitmemory 400k -p <pid> ...
5
votes
5answers
2k views

How do you free up resources in Ubuntu?

What steps do you take to make a vanilla Ubuntu system run faster and use less memory? I'm using Ubuntu as the OS for my general purpose PC, but it's on slightly older hardware and I want to get as ...
7
votes
3answers
504 views

How to track down memory spikes?

I have an app running on rackspace cloud (ubuntu 10.04). For some reason, over the last 3 nights, the memory has been spiking and then leveling off for about 7 hours before eventually falling off. ...