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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getting kernel: pci 0001:02:00.0: BAR 0: can\'t allocate mem resource [0x60100000-0x600fffff] on reboot

On rebooting the board we are getting following errors: err: kernel: pci 0001:02:00.0: BAR 0: can\'t allocate mem resource [0x60100000-0x600fffff] Warning: kernel: aer: probe of 0001:02:00.0:pcie01 ...
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2answers
3k views

What is the appropriate value of vm.swappiness when using zram?

I'm using zram on my computer as a compressed RAM-backed swap. When the system needs to swap something out, swapping it to a zram-backed swap file is more or less equivalent to compressing that data ...
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2answers
1k 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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2answers
83 views

How to identify cause of large buffer memory usage?

I have a production machine running a 2.6 kernel (Centos 6.7) with 64 GB of RAM of which 18 GB is apparently used for buffer memory. I am interested in identifying specifically what that 18 GB is ...
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1answer
142 views

Is there a way to know how much memory Linux Os is using?

I am looking for a way to know the size of the memory that Linux os is using (I'm not worried about the other applications memory size). I am using Ubuntu distribution (Ubuntu 15.10). Thanks for your ...
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0answers
120 views

Why are slab objects not reclaimed automatically

Everyday after a full system backup, various programs are failing with read errors until I run echo 2 > /proc/sys/vm/drop_caches to free reclaimable slab objects. For example, here's the output of ...
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3answers
148 views

Is it possible to impose some kind of soft limit on the memory consumption of processes?

I reckon it's not such an uncommon problem: one process allocates massive amounts of memory (be it due to a memory-leak bug, because you try to process an infeasibly large input file, or whatever). ...
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16 views

What does “wrap around” mean in DMA?

Recently working on a PCI driver project and trying to understand the Scatter Gather DMA. In my project, the PCI device(in a PC's PCI slot) is the DMA master and I want to do a DMA write to the PC's ...
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1answer
65 views

Does my system use all available RAM?

I installed 16GB of RAM on a motherboard that shouldn't take it. Should I buy a better motherboard or change anything at all? It seems to be working fine. Memory: Crucial Ballistix Sport "(8GBx2) ...
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2answers
86 views

Is there a way to free memory? [duplicate]

I remember, back from my days with Windows Vista/7, that there was a tool called memclear or memclean that would free some memory by invoking the NT garbage collection API. Probably it cleared cache ...
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1answer
32 views

How to find hugepage size on system?

I am getting following two different result. which one i should consider for Hugepage? [root@server ~]# getconf PAGESIZE 4096 [root@server ~]# grep -i hugepagesize /proc/meminfo Hugepagesize: ...
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1answer
171 views

How to find out how much memory lxc container is allowed to consume?

I'm trying to make ansible set InnoDB buffer pool size to some percent of available memory. But ansible_memtotal_mb and free report how much memory the host has. How do I figure out how much memory is ...
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20 views

Best small distro for ROM burning of the system for an embedded system

I am building a specific device and I would like to know what Linux based small distribution would be good when I would choose the put-Linux-on-the-ROM route, so, that the system is not possible to ...
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2answers
103 views

It's safe to remove /var/log files

Today i was freeing my space in my Linux mint 17. In Disk analyzer i found that /var/log uses 54+ GB. So what does /var/log used for ? is it safe to delete /var/log ?
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How to check if an application uses my video card memory?

We can check the core, cpu utiliztion, memory etc of a particular process. Can we check if it uses video card too and if it is how much memory it is using?
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4answers
18k 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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1answer
559 views

What's the difference between ioremap and file operation mmap?

I'm currently working on a PCI device driver for Ubuntu. I have some example code about PCI driver, but I have difficult on understanding the ioremap and file_operation.mmap. The description of file ...
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47 views

How can I profile/benchmark RAM performance?

I would like to know if my memory hardware is a bottleneck of my system performance. I am dealing with really old hardware (late 2000). If there is room for improvement, I would like to upgrade. ...
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5answers
82k 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 ...
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0answers
33 views

how to enable 1MB dma-kmalloc

I'm running a ubuntu 15.10 VM and testing code that will allocate 1MB dma buffers. However, from the /proc/slabinfo, the max that can be allocated is 8K dma-kmalloc-8192 0 0 8192 4 ...
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1answer
25 views

What is taking up my memory in my Linux virtual machine

I'm trying to debug an application (mongodb) memory usage on a a virtual machine. mongod, is taking 11% of memory. I know this by using top but when I want to see how much of my 7.5GB is free, I ...
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Working my way through dmesg output on a custom 3.5.4 kernel

Having read this thread here: What does the Virtual kernel Memory Layout in dmesg imply? It sounds like 'lowmem' is exclusively meant for kernel-space. [ 0.000000] virtual kernel memory layout: ...
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2answers
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What tools can I use to diagnose the exact reason for laptop slowness? And how do I use those tools?

I am running Linux Mint 17 on my laptop. When using applications (mainly Web Browsers) the machine freezes for little time periods. The CPU indicates 100% usage at such times, but this only seems to ...
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87 views

Boot rescue kernel at high memory address using kexec on arm

Summary: Crashkernel boots at 512MB address in RAM with kexec -e/-l but not with kexec -p - why? Embedded platform with Marvell Armada XP (MV78460) (ARMv7 with 4 cores) and 1GB of RAM. production ...
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107 views

Is unreclaimable memory allocated to slab considered used or available cache?

After evaluating /proc/meminfo, I see the following information: $cat /proc/meminfo MemTotal: 197852592 kB MemFree: 64755992 kB MemAvailable: 65655112 kB Buffers: 4388 kB ...
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52 views

Where is my memory being used?

Only 28G is being used by buff/cache. $free -h total used free shared buff/cache available Mem: 188G 87G 72G 17M 28G ...
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1answer
89 views

How do you prevent system from freezing when memory is used up?

I've been running a process (gdb) that can easily use up all my ram and swap space. Every time that happens the whole system becomes very non-responsive and Xorg will barely update, I can't swith to ...
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1answer
124 views

How to run free command by crontab

I want to run this command: free && sync && echo 3 > /proc/sys/vm/drop_caches && free -m by cron. That way I can free my RAM and cache in an Ubuntu system. I'm using ...
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1answer
38 views

How do I check how much total memory my VM has? [closed]

I've tried /proc/meminfo but my permission has been denied.
3
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1answer
188 views

What is the usual Allocation unit for a process on Linux?

I'm currently studying memory management in Operating Systems. Allocation Unit is the smallest unit of memory the OS will give to any process. I've read in this page, in the 'Memory allocation ...
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0answers
46 views

What does it mean when a private VM page is none of `rwx`?

UPDATE: It's a padding: every such non-rwx area is preceded with a readable and/or writable area and together they constitute a 64Mb segment (for 64bit architecture). A relevant question on SO: ...
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1answer
455 views

find: cannot fork: Cannot allocate memory

I want to delete 1 file at a time from my directory which contains so many files,So i want to remove 1 file at a time. Just to avoid too many reads and failed at too many arguments. find ...
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1answer
55 views

Shared memory v/s physical memory

I have a C++ process which is using shared memory to store and transfer data between its child processes. I want to check the shared memory usage while the parent process is executing just like top ...
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1answer
162 views

How can two identical virtual addresses point to different physical addresses?

Following a fork() call in Linux, two processes (one being a child of the other) will share allocated heap memory. These allocated pages are marked COW (copy-on-write) and will remain shared until ...
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1answer
37 views

difference between inactive and free memory in output of FreeBSD top utility?

top -d1 displays following SDRAM usage statistics on one of my older machines: 125M Active, 42M Inact, 51M Wired, 17M Cache, 34M Buf, 2720K Free In total, there is 256MiB of memory installed. ...
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1answer
61 views

Finding memory corruption bugs in Linux and FreeBSD

In windows, we can enable page heap verification using gflags to catch memory corruption bugs more easily. Is there a similar service/program for Linux and FreeBSD operating systems?
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4answers
26k views

How to Determine the Amount of RAM Slots In Use?

I forgot how many RAM modules are installed on my laptop. I do not want to unscrew it but want to look it up on the console using bash. How do I gather this information?
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8answers
5k views

cron Vs. sleep - which is the better one in terms of efficient cpu/memory utilization?

The Case: I need to run some commands/script at certain intervals of time and for this I have two options - 1. set up a cron-job or, 2. implement a loop with sleep in the script itself. Question: ...
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2answers
2k 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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0answers
76 views

wProcess killed by OOM killer when plenty of memory apparently free

I'm working on an embedded ARM-based platform. 32-bit, 512MB of RAM, no swap. Linux 3.10.53 (some variety of Ubuntu, if that's relevant). Some code I'm working on is getting consistently oom-killed, ...
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1answer
41 views

Hardware specs for Linux machine for cluster administration [closed]

I have just started as cluster system administrator and was asked to choose some features to get bought a personal machine to work on, and most intensive calculations will be perform in the cluster. I ...
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2answers
723 views

Does sync command remove the dirty cache in the memory?

I am aware that sync command flushes the dirty cache into disk. I have run free command first, then sync, and then free again. The result of latter free command shows more free memory available than ...
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3answers
2k views

How to monitor use of Huge Pages per process

I'm trying to determine which process is using a large number of Huge Pages, but I can't find a simple Linux command (like top) to view the Huge Page usage. The best I could find was $ cat ...
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0answers
27 views

Debian - Memory usage [closed]

I all, I'd like to understand what happens in this system. Running top I get: KiB Mem: 496948 total, 460012 used, 36936 free, 68604 buffers and in the process list the process that ...
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1answer
496 views

What happens after a page fault?

When a page fault occurs in a Linux system, the interrupt-handler has to figure out the reason why the page fault happened. But how ? Is there anywhere a special number for that !? If yes, where is ...
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1answer
68 views

How to read .vma files?

I am trying to read a .vma file but no luck finding an application to do it on Linux.. I tried to google it but it didn't work out.. The file was produced by Volatility on Ubuntu Linux 12.04 using ...
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Memory consumption over variable period of time

There are a number of questions on this StackExchange about memory consumption, notably: How to check which process is using most memory How to display top results sorted by memory usage in real ...
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3answers
2k views

Linux / JVM - OutOfMemoryError: unable to create new native thread

I have a memory problem with a Linux server (CentOS). It is a VM. Below is the context. It has 70Gb of RAM. There are 2 tomcat running on it. One tomcat is given a heap of 13Gb and the other one a ...
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0answers
180 views

Portable way to parse /proc/meminfo

I'm having trouble finding a generic code that work, here, for both CentOS 5/6 and CentOS 7 versions pc the /proc/meminfo file. I Want to compute the "Real Used memory" like free does. (amounts ...
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0answers
89 views

Dump XEN guest memory image

I am new into memory forensics thing and I am trying to dump a memory image from a XEN guest (Ubuntu 12.04 x64 - domU) in order to analyze it on dom0 (Ubuntu server 12.04 x64) with volatility . For ...