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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How to Study Effect of zram on Memory Size and Paging?

Situation: to study the effect of zram's virtual memory compression (wiki) on memory's size and its speed Motivation: I experience no effect on the memory's size but increased amount of errors from ...
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“swap cache” of vmstat vs. “SwapCached” of /proc/meminfo

On my Fedora 24, I executed two commands to examine the memory information, however, I got two different results about swap cache's size. The first command is as follows: [root@localhost ~]# vmstat -...
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42 views

Less RAM Aailable than installed on Centos 7

I can't seem to figure out why do I have less RAM usable than installed. I am running 64bit Centos 7 with 1 RAM module of 4096MB on a Lenovo x230. Some information from the machine in question: $ ...
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14 views

Kernel module crashes when reading memory [migrated]

If I know the physical memory of data, because it was placed there by a memory mapped peripheral, how do I access it in a kernel module? My first instinct is to make a pointer int * addr; and ...
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1answer
24 views

performance comparison of multiple commands excutions

I've got three different programs written in three different languages, and I'm trying to compare their performance in terms of runtime, and memory consumption. What I'm looking for is some command ...
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31 views

Is there a more efficient way of defragmenting Linux memory other than rebooting?

I am running Gentoo Linux with kernel 4.4.8-hardened-r1, QEMU-KVM version 2.5.1 and 3227 MB of system-visible RAM (without considering RAM taken by BIOS and my AMD APU's graphics). I have a VM that ...
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42 views

Program execution in Linux [closed]

I would like to know what sequence of events are followed when a program (Say a C code image) is executed in Linux based OS. The memory map of the executable image of program is made using structure ...
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2answers
69 views

Where the remaining memory of vm.overcommit_ratio goes?

If I disable memory overcommit by setting vm.overcommit_memory to 2, by default the system will allow to allocate the memory up to the dimension of swap + 50% of physical memory, as explained here. I ...
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25 views

Questions on /dev/mem, dumping using dd, and .bin and .rom formats

Following @ack 's answer on How to dump BIOS data to a file I would like to know: 1) when one is dumping memory from /dev/mem, is the file data in binary or some other format? I have done a dump ...
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36 views

How to convert from virtual address to physical address and back? [migrated]

I'm given a task to write an application that will talk to a device. However this is not a driver since device is still being developed and the application is intended to exercises its first revision. ...
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32 views

Flash an OS to an eMMC, from uSD with larger capacity than eMMC

With a Debian distro installed into a 8GB uSD (although uSD memory is almost free), I need to flash this distro into the 4GB eMMC of a BeagleBone Black board, based on AM335x SoC. The S2 switch ...
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i whant to clean the shared and the buff/cache memory [duplicate]

I want to clean the shared and the buff/cache memory, I'm not expert in linux but I want to learn. I have 2 gb of ram when i go through firefox the memory used is 900-1000 mb is this normal?? ...
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33 views

Embedded Linux OOM - help with lost RAM

I have little Linux system with 256MB RAM. I'm little bit confused, where the RAM may be lost? It is running old linux kernel 2.6.38 and I'm not able to ubgrade it (some specific ARM board). SHM and ...
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41 views

GNU/Linux OOM (out of memory) freezes - solution ideas

Explanation While working with older machine with swap on and 2 GB ram, I frequently encounter behaviour well described as freeze: here, what is the best way to prevent out of memory oom freezes on ...
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2answers
35 views

How to use top in a shell script to track memory consumption of a process?

I was wondering if there was a way to use top or another program to track the memory consumption of a script I will be running. I was using runtime.totalMemory - runtime.freeMemory But that'...
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37 views

How to specify memory region for ramdrive

We are setting up a Linux based benchmarking cluster. Each node is going to be a headless, diskless machine, booted via tftp, the OS copied to a local ramdrive, and the same ramdrive is used as local ...
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1answer
676 views

When files are being moved are they stored in a memory?

When I move a file using the mv command, is this file first read, fully cached into a memory and then saved as another file? Or is it the same as writing while read line; do echo "$line" >>...
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3answers
107 views

Get chrome's total memory usage

Since google chrome/chromium spawn multiple processes it's harder to see how much total memory these processes use in total. Is there an easy way to see how much total memory a series of connected ...
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27 views

Entire Harddrive to linux swap

I have an old hard drive that is less than 50Gb and a computer that only has about 4Gb of ram (and ~250Gb main HDD). I was thinking about using the second drive as an entire drive linux-swap partition....
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1answer
37 views

Disable OS-level caching

I want to be able to prevent the OS from caching in memory either: A particular file, or Any file a particular process accesses (i.e. by specifying a pid) Either would be helpful since I don't ...
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39 views

Total memory decreased when increasing swap file?

I am running a low-end server with about 1GB RAM and I was trying to optimize my ram. But after increasing my swap file and emptying the buffers, my total ram, judging from free -m, have lowered from ...
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1answer
31 views

Virtualbox memory not reflected in its cgroup

I've trying to limit the amount of memory a user can use using cgroups (using Ubuntu 16.04 with systemd). After setting the MemoryLimit property of user-.slice I can see the change reflected in its ...
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1answer
34 views

Do .so files get loaded as a whole into memory?

When a program causes a .so file to be loaded into memory, does is get loaded as a whole, or or does it only load the necessary "chunks"?
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2answers
46 views

How much memory is a specific user using

Is it possible to find out how much memory I am using on a multiuser linux machine? I want to know whether I am using a lot of memory and possibly inconveniencing others, so I can shut down my ...
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45 views

Possible slab memory leak related to bio and btrfs?

I'm currently running a rebuild on a btrfs NAS (~20TB) that had a drive failure. It's going to take a few days. My problem is about once every 24 hours the RAM filled up and the kernel starts killing ...
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1answer
36 views

What does a “Synchronous” type detail mean in dmidecode?

I'm curious if my 2 DIMMs are running dual-channel or not and use: dmidecode -t 17 ... Type Detail: Synchronous ... What does a "Synchronous" type detail mean? Dual-channel?
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66 views

Debian 8 performance problems with good hardware

I bought about 6 months ago a good laptop (Lenovo ThinkPad E550 : Intel Core i5-5200U, 8 GO DDR3, AMD Radeon R7 M260) and installed Debian Jessie with Gnome 3 (no unity) on it. The system worked fine ...
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56 views

How to determine which files are necessary in /bin, /lib, /var, etc.?

I'm currently trying to get an image working for a network boot using somebody else's file contents. The previous images I made keeping all original files present were way too big, so I need to shrink ...
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1answer
52 views

Limit CPU and Memory usage for C, Java programs at system level

I am building an online code editor for C and Java. Chances are users will write infinite loops. Is there any way I can limit the cpu and memory utilization of these processes at system level settings ...
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2answers
43 views

U-Boot shell - show memory usage (like Linux free command)

Is there any way of displaying memory usage from U-Boot? I mean operation memory - like sdram - not mmc.. Ideally from shell but I can be happy also with C command as I compile U-Boot myself.
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1answer
39 views

How to obtain counters for swap-in/swap-out on Linux?

I'm trying to obtain counters for swap-in/swap-out activity on CentOS 6. The intention is to feed raw data into RRDtool to generate graphs, and use it to generate alerts. I've had a look at common ...
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1answer
131 views

What page replacement algorithms are used in Linux kernel for OS file cache?

Linux uses the unused portions of memory for file caching, and it cleans up the space when needed. My question is about how it picks a victim page for replacement? There are various algorithms (LRU, ...
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23 views

Can I deny use of swap space to a specific process (and have it just get killed)?

While developing some software, a program under test sometimes eats all the memory, then proceeds to yomp into the swap space and start thrashing the disk, leading to a predictable drop in ...
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2answers
122 views

Top command output explanation (in embedded system)

Can someone please help me understand the output that I get from the top command? This is the point that the oom-killer is invoked and kills my main application. What exactly is under the VSZ and %VSZ?...
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1answer
29 views

How to run a process and find how much memory it uses? [duplicate]

I regularly use time to find out how long a process takes. Is there an equivalent command for memory? The usual ways to find out how much memory a process takes (ps,/proc/meminfo, etc.) work fine for ...
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1answer
76 views

Memory not used any more but still allocated

I have something kind of weird going on with memory. I have Ubuntu 14.04 servers with Zimbra 8.6 with kernel (for this one) 3.13.0-37-generic. But I have already seen the problem with other kernels. ...
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4answers
85 views

Get total memory size on sun os through kstat

I have sun os there Following commands are not available prtconf prtdiag psrinfo The only command which is working is kstat. Can any one please help me on finding the total memory size using only ...
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1answer
74 views

Keep a process in RAM (prevent it from swapping)

I want to keep a process in RAM. It should never go into swap. Is this possible? The process is a Java program. I'm running CentoS 7.
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How to mmap file w/ HUGE_PAGES to specific memory location (via “memmap=4G$4G”)

Presently working: Device driver to mmap to specific memory location (isolated by boot parameter "memmap=4G$4G") via the remap_pfn_range call. Desired solution: Same/similar outcome using 2M pages ...
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21 views

How does disabling data journalling speed up the file system?

How exactly does disabling journalling give a better performance in case of Linux (ext4)?
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2answers
87 views

Disk busy 101% all the time

I have an OpenNMS Linux server which is having poor disk performance. The machine is a EC2 inside a VPC. atop shows: iotop shows: How do I reduce the IO numbers and bring down the disk ...
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1answer
30 views

How to know what exactly is being written or which process is keeping my storage disk busy?

I have a server , which has gone rogue(not really), i ran nmon and saw that its Disk utilization is BAD, its 100% busy writing!! Here is the output : Can someone tell me what is keeping my disk ...
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53 views

How can I mount remove /dev/mem to local

This question is relate to this, but more general. Currently I mount remote root by sshfs sshfs -o sshfs_sync,sync_readdir,reconnect,follow_symlinks,direct_io,sync_read root@pi:/ pi /proc is ok, ...
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3answers
77 views

When interrupting a process, does a memory leak occur?

Lets say I created a program in c/c++, where I manually allocated some variables. Then while running the program, I send an interrupt signal (Ctrl-C). Are those variables freed from memory, or will ...
3
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1answer
131 views

free command output: gentoo (redhat?) vs debian

I noticed there is a difference between outputs of free command: On debian: $ free -h total used free shared buffers cached Mem: 4.0G 3.4G ...
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OOM Killer: Processes have a score of over a 1000

All top links when Googling for OOM score seem to indicate that the values must be between -1000 and 1000. I tried to verify that with a simple cat /proc/*/oom_score | sort -n | less and I ...
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Why does .text region of shared libraries is not flagged as VM_SHARED?

When I'm using shmem/mmap to share memory between processes I can see with pmap that it creates virtual memory area that marked as shared. Example: Address Kbytes RSS Dirty Mode ...
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40 views

How to calculate the amont of kernel memory allocation on Linux?

My system has 128GB physical memory. However, free -h said I have 125 G total memory. [root@rhel7 ~]# free -h total used free shared buff/cache available Mem: ...
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671 views

Finding the source of CoW page faults on OS X

I'm trying to find the source of CoW page faults in some C code on OS X. I would like to use the vminfo DTrace provider, but vminfo isn't available on OS X. On Linux, I can use SystemTap to print a ...
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88 views

How do you change the Hugepagesize?

How can I change the pagesize for Hugepages on Linux? I'd like to increase it to 4096 kB or 8192 kB. I'm working specifically with Centos and Amazon Linux. $ grep Hugepagesize /proc/meminfo ...