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3
votes
1answer
16 views

Shared library mappings in /proc/pid/maps

Why does /proc/pid/maps contain a few records for the same library ? Here is an example: 7fae7db9f000-7fae7dc8f000 r-xp 00000000 08:05 536861 ...
1
vote
0answers
23 views

Print kernel memory layout

Userland memory layout can be inspected by looking into /proc/self/maps. I am wondering if there is a similar facility allowing to inspect runtime kernel memory layout?
3
votes
2answers
71 views

Physical Address Extension - how do virtual addresses work?

I'm running Debian Linux. uname -m says i686 which means 32-bit architecture machine with pae flag enabled. getconf LONG_BIT is 32. Installed RAM capacity is 6GB. My /proc/cpuinfo has an entry ...
3
votes
1answer
41 views

Kernel address space layout

Userland address space is well documented, which includes segments like heap, stack, .text, .bss, etc. But there is not enough documentation on kernel address space. Since certain virtual address is ...
0
votes
0answers
31 views

Why process is killed while a lot of memory is free?

I am running a python script in ipython. This script will take about 8GB RAM. The system has more than 80 GB free RAM but the swap is nearly 0. My script was killed after it runned for a while. I want ...
2
votes
0answers
29 views

How do I vmtouch a directory (not the files it contains)?

The vmtouch(8) tool allows locking a file or files in memory. It has recursive mode, but the directories are used just for discovering files and are not locked themselves. How do I lock a directory ...
1
vote
1answer
78 views

Why does my process take too long to die?

Basically I'm using Linux 2.6.34 on PowerPC (Freescale e500mc). I have a process (a kind of Virtual Machine that was developed in-house) that uses about 2.25 G of mlocked VM. When I kill it, I notice ...
0
votes
0answers
37 views

Is High Virtual Memory usage a problem or may cause problems?

In our server, we have a python based code that listen ports. The amount of Virtual Memory it uses is increased greatly with time Like: USER PID %CPU %MEM VSZ RSS TTY STAT ...
3
votes
1answer
55 views

How do I forbid access to physical memory in Linux?

I'm on an embedded system (Zynq from Xilinx. It uses ARMv7, Cortex-A9), and running Linux. I need to ensure that no access to a certain physical memory range is ever made, either accidentally by the ...
0
votes
0answers
19 views

Page Fault Frequency Algorithm - Compute number of frames and mean resident set

I'm reading about Page Fault Frequency algorithm but I don't understand how can I compute the number of frames. For example I have my reference string: 112233444412412214432255543 and control ...
1
vote
1answer
35 views

Case study of virtual memory management

Need help in understanding virtual memory concept. When a process requesting for 2GB mapping onto the virutal memory in Linux environment of 4GB ( 1GB Kernel : 3GB Userspace), when already another ...
0
votes
0answers
32 views

fast way to find the address range from the given info

I have a question, If I am given some memory devices with size specifications, how do i map it to address range quickly. if the address space is of 32 GB. Ex: ROM - 1Mb 3 RAMs - 2 GB each 2 FLASH - ...
1
vote
1answer
82 views

Is the Linux kernel affected by paging?

Is the whole kernel always loaded to RAM whatever the size of the RAM? In other words, can the Linux kernel be affected by paging (some part of kernel reside in virtual memory)?
2
votes
2answers
59 views

How to get the virtual storage size of a process continuously?

We all know that top command monitors the running processes continuously. I have an application that is running continuously in an embedded Linux and I need to monitor its VSZ (Virtual storage size) ...
0
votes
1answer
31 views

/dev/mapper/vg00-var maxing out

Over the past few years we have had multiple Linux servers have the same problem time and time again: our /dev/mapper/vg00-var folder maxes out at 100%, which means all sites on the server die. We ...
10
votes
1answer
149 views

Does anyone actually use and benefit from transparent huge pages?

I've been struggling with transparent huge pages performance issues of late, and noticed many database systems recommend turning it off. I am talking Oracle, Postgresql, MySQL, Cassandra, NuoDB, ...
2
votes
0answers
46 views

JVM low-memory tuning

What command-line options would provide the lowest memory-footprint JVM, in OpenJDK, or possibly other JVMs (Linux/Debian)? I'm willing to disable JIT, live with slow or choppy garbage collection, ...
1
vote
0answers
39 views

In the Linux Kernel what file/process controls the assignment of permissions to memory pages?

A given memory page may be writable, readable or executable. What kernal source code file in the linux kernal describes the setting of these rights? What process or kernal data structure would set the ...
-1
votes
2answers
236 views

Generate major page faults

Is it possible to generate major page faults in the linux kernel at will? Can a program be written such that it is guaranteed to cause a major page fault on it's execution.
1
vote
1answer
70 views

Linux always hangs when out of physical memory

I'm using ArchLinux, with 3.18.6-1 kernel, when a software uses more than physical memory (when total memory used is >5.8 GB), it always lags, unresponsive, and all that I can do is reset the ...
2
votes
0answers
65 views

How can I let high priority processes continue when low priority processes are causing free memory to be low

Ok I'm not sure if this is the correct place to post this. It is more of a 'why not' question than a 'how to' one (assumption is that it isn't/can't be done). Why don't we allow RAM to be partitioned ...
0
votes
2answers
80 views

Are the size of a memory page and the size of a file system cluster always the same?

From http://en.wikipedia.org/wiki/Page_%28computer_memory%29 A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in the page ...
5
votes
1answer
236 views

When does swap start to be used? When does a process get an out of memory error and be killed?

When does swap start to be used? Is it when the memory is fully used? Or when the memory hasn't been fully used? When does a process get an "Out of memory" error and be killed by the kernel? is it ...
3
votes
0answers
172 views

Why does saving a KVM-QEMU VM requires additional memory?

I have three VMs running on Red Hat Enterprise Linux with 8 GB RAM, each of the VMs has 3 GB allocated, and I also run a 512 MB VM. If we also consider the guest OS's memory usage (usually 1.5 GB due ...
1
vote
0answers
324 views

Xorg consuming 1.1GB, is it a leak?

I am facing a problem wherein Xorg starts to consume more and more memory and finally eats up the whole swap space. As shown below, Xorg's virtual memory is about 1.1GB. My system runs only one GTK ...
0
votes
1answer
122 views

What is the difference between MAC OS X “Virtual Memory” and Linux/Unix Swap? [duplicate]

I would like to understand the difference of MAC OS X "Virtual Memory" and Linux/Unix Swap. I ask this because I observed that MAC OS X "Virtual Memory" seems to work way more efficient (in desktop ...
1
vote
0answers
409 views

About mem and vmem

I am working with a cluster machine running under linux. I have a shell script that uses mpirun to submit my jobs to the cluster machine. In that same script, I can choose the number of nodes that ...
1
vote
3answers
2k views

Actual memory usage of a process

The following are the memory usage of mysql and apache respectively on my server. As per the output of pmap say, mysql is using about 379M and apache is using 277M. [root@server ~]# pmap 10436 | ...
1
vote
1answer
85 views

A simple definition for Virtual Memory

How correct is this picture that I drew up if I am to explain Virtual Memory to some of my colleagues? There are hundreds of documents available online explaining virtual memory, but I am yet to ...
0
votes
1answer
343 views

Opening files of size larger than RAM, no swap used.

I found myself asking this question while doing small experiments and reading upon how memory is managed in Linux. I have a 64-bit Centos 6.5 machine with 512M RAM and 1G SWAP. I created a 1GB file ...
1
vote
1answer
176 views

AIX Memory Limits

I cannot find these numbers anywhere on the IBM Web site or even random blogs that Google finds. Questions What is the maximum physical memory size a POWER7 CPU supports? What is the maximum ...
0
votes
1answer
49 views

«nm» shows zero VMA: where is the symbol will be mapped?

I am look at the functions of my compiled application via «nm» — I need to find an address to set a breakpoint to the «send()» function. The problem is that this function accordingly to «nm»'s output ...
1
vote
1answer
87 views

benefits of huge pages on a laptop/desktop

I have read about huge pages and its the (potential) benefits. However, I am still confused whether this is mostly beneficial on a server with lots of RAM, or if it can be advantageous on a ...
2
votes
0answers
102 views

Disk page cache size in Linux for integrity purposes

I am trying to bound corruption in a block-based disk format in the presence of plausible machine failures in a Linux-specific application. That is, the file is read and written in application-defined ...
30
votes
2answers
2k views

Why did powering down my machine after a bad `rm` save my files?

Classical situation: I ran a bad rm and realized immediately afterwards that I had removed the wrong files. (Nothing critical and I had tolerably recent backups, but still annoying.) Knowing that ...
1
vote
0answers
51 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? ...
0
votes
1answer
147 views

to print address space of a process in ubuntu 12.04

How do I print an address space of a process by taking the process' PID?
1
vote
1answer
122 views

How logical address of one process differs from the logical address of another?

I am a newbie. I am reading Understanding Linux Kernel. There, I am trying to understand how logical address got translated to physical address. To my understanding, I believe logical address got ...
1
vote
1answer
206 views

Malloc and Paging

When a user process invokes malloc(n), are there any physical pages allocated to the process? I believe No since malloc allocates from the heap. Is this correct?
2
votes
1answer
302 views

Is a page contiguous in the virtual address space or physical memory or both?

Wikipedia says that: A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in the page table. It is the smallest unit of data ...
3
votes
4answers
2k views

How much RAM needed for preventing use swap?

At my system always available some "Free" and "Inactive" memory, but sometimes system move couple megabytes to swap. Per night it maybe around 100MB, but for a few days in swap could be more than ...
7
votes
2answers
2k 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 ...
2
votes
0answers
195 views

Virtual kernel memory layout in dmesg linux kernel 2.6.31

I'm working on a embedded linux project for ARM architecture, kernel version is 2.6.31.12-rt21. In dmesg, I cannot see the virtual kernel memory layout like this: virtual kernel memory layout: ...
0
votes
2answers
719 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 ...
5
votes
2answers
327 views

1GB huge page - Is writing occurring in 1GB chunks?

I'm trying to understand the relation between huge page size and how data is actually being written to RAM. What happens when a process uses a 1GB huge page - does writing occur in 1GB chunks? I ...
4
votes
1answer
81 views

Memory consumption of a script

Is there way to check the memory (physical & virtual) consumption of a script, of course in the moment of its execution. Calculating the used memory minus the used memory before and after the ...
1
vote
1answer
1k views

Clear Memory Cache on Amazon EC2

In our project we have a few tests which run for about 3-4 hours continuously. In due course, the tests fail as they couldn't find enough memory. On googling, I found that running the following ...
3
votes
1answer
48 views

program executing for 2 days

I have a java program which implements the Hungarian algorithm. I made changes to the existing code in such a way that the input is read from file. I have a pretty huge input around 32,000 rows for ...
1
vote
1answer
1k views

Iotop shows swapin but vmstat si is zero

I run iotop and vmstat on a CentOS server. Under some load the iotop swapin column starts to display values around 5% to 20% for some processes. But vmstat si field remains at zero. I thought that ...
2
votes
2answers
363 views

Is there a good benchmark for virtual memory performance?

Aside from running memory benchmarks, has anyone used a benchmark that stresses the virtual memory subsystem? I'm curious to see how performance differs in virtual machines with and without EPT ...