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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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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Debian 8 performance problems with good hardware

I'm finally asking for help after some research, 'cause my problems are getting me crazy... I bought about 6 months ago a good laptop (Lenovo ThinkPad E550 : Intel Core i5-5200U, 8 GO DDR3, AMD Radeon ...
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50 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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23 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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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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26 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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60 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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18 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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54 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 ...
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1answer
25 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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55 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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48 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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50 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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19 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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66 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
27 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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34 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
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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 ...
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1answer
76 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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23 views

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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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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660 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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1answer
48 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 ...
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36 views

-/+ buffers/cache & Swap

When should the usage of swap get started? or How do I know that my swap is being used? At least some times if not always, considering the default swappiness of 60 Also, why does free offer to omit ...
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vmstat -s command fields meaning, specially “pages paged in” vs “pages swapped in”

Most of the fields are understandable but can someone please explain me the difference between "pages paged in" and "pages swapped in"?. I'm pretty sure that swapping is when the entire process is ...
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awk memory leak?

Base on this I'm running the command < /dev/urandom hexdump -v -e '/1 "%u\n"' | awk '{ split("0,2,4,5,7,9,11,12",a,","); for (i = 0; i < 1; i+= 0.0001) printf("%08X\n", ...
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1answer
35 views

Eviction of Disk Cache in Memory

Say RAM is 100% used, some by disk-cache and some by applications. There is plenty of swap (on a hard disk available). If Linux decides to evict a page that contains application data, it would be ...
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51 views

How to log every memory access in linux of a single program? [closed]

I am trying to analyse the memory usage of a single program and need a list of every access the program made, so basically i need something like Valgrind but with a complete output.
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1answer
31 views

vm.swappines parameter influence on system without swap partition

I run across following definition of vm.swappines: The swappiness parameter controls the tendency of the kernel to move processes out of physical memory and onto the swap disk. So, if I have ...
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1answer
72 views

How to debug an Out of memory crash

Recently one of my CentOS6 server crashed because of an Out of memory Error: It seems to be related to the postgres database used by java web-applications (deployed on tomcat). But I cannot find ...
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137 views

Understanding and configuring Cache Memory

I have few questions about Cache Memory In my system "free -h" command gave me below output, total used free shared buff/cache available Mem: 7.6G 2.1G ...
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Gentoo Hardened eats 3 GB of memory after running for ~12 hours with very few processes running

I'm running Gentoo Hardened AMD64 using kernel 4.3.3-hardened-r4. With my system only running some basic daemons like wpa_supplicant, cron or DHCP, and with an X session with only Windowmaker, GKrellM ...
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1answer
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Why do different instances of the same program use up different amounts of memory?

I simply started 5 instances of the default xterm, doing nothing in them at all. Looking at the output from htop, it appears that these instances use different amounts of RAM: VIRT RES ...
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Logging memory issues with Cron

I'm trying to log memory errors/issues using cron, however I'm still unsure how to do this. I'm new to cron, but I entered our system with it already using the tool. We've been having memory issues ...
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36 views

Why does OOM-killer sometimes fail to kill resource hogs?

If I type in my shell x=`yes`, eventually I will get cannot allocate 18446744071562067968 bytes (4295032832 bytes allocated) because yes tries to write into x forever until it runs out of memory. I ...
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1answer
59 views

Convert meminfo kB to bytes [duplicate]

To convert the readings in /proc/meminfo from "kB" to bytes, should I multiply by 1024, or 1000?
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1answer
45 views

What is difference between cached memory and used memory?

In my System Monitor panel applet in Linux Mint 17.3 Cinnamon, it shows me memory usage of used memory and cached memory combined, whereas in the system monitor application, it just shows used memory, ...
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2answers
91 views

C++ app. with mmap kills kernel? (kernel panic with mmap)

In my C++ program where intensive disk, network I/O and even CPU computation occur, I am using memory mapped region as an array. With very small data, it works fine. However when I ran the program ...
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2answers
51 views

What is the default memory allocation for shell process by linux

What is the default memory allocation for shell process by Linux , i mean is there any upper limit for shell process or any process.
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1answer
47 views

Memory leak on webserver

So I have lately been have some server performance issues. Currently we are running a Fedora server with 4GB and 160gb disk space. We are pretty much capping out the disk, with all of the files we ...
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1answer
103 views

How can I get the amount of available memory portably across distributions?

The standard files/tools that report memory seem to have different formats on different Linux distributions. For example, on Arch and Ubuntu. Arch $ free total used free ...
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1answer
67 views

Exceeding memory issues on server using PHP

PHP has memory limits set at a global level in the PHP.ini file. I also know that they can be configured at the local level. Our memory limit for a query is set to 132MB, but we keeping getting ...
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1answer
45 views

Get current memory usage of a tmux session

As the title says. I need a way to the used memory of a current tmux session. I am not sure if that is even possible. I am using tmux to start multiple minecraft servers I'd like to know each servers ...
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why we need ram if we having swap memory? [closed]

In Linux we have a swap memory right. the system will use swap memory if ram memory is full.then what is require of RAM we can use directly swap memory.
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2answers
571 views

High memory usage but no process is using it

I run free -m on a debian VM running on Hyper-V: total used free shared buffers cached Mem: 10017 9475 541 147 34 909 ...
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1answer
52 views

Downsides of processes with high virtual size but low RAM and GPU memory use

I have noticed that some of my processes take a lot of virtual size in my computer. I understand that the virtual size of a process is the sum of memory it is actually using, memory it has mapped into ...
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1answer
32 views

How does OSX handle Out of Memory conditions?

Linux uses the OOM killer; what do Macs do?
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115 views

FDT relocated by U-Boot cannot be accessed by Linux (in highmem)

We run a customized version of U-Boot on an ARM-based embedded system and would like to load Linux 4.3 with a device tree blob. The system features 1GB of RAM of which the top 128MB are reserved for ...