Questions tagged [memory]

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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9answers
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How to display `top` results sorted by memory usage in real time?

How can I display the top results in my terminal in real time so that the list is sorted by memory usage?
180
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12answers
144k views

How to fill 90% of the free memory?

I want to do some low-resources testing and for that I need to have 90% of the free memory full. How can I do this on a *nix system?
177
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7answers
220k views

How to display meminfo in megabytes in top?

Sometimes it is not comfortable to see meminfo in kilobytes when you have several gigs of RAM. In Linux, it looks like: And here is how it looks in Mac OS X: Is there a way to display meminfo in ...
147
votes
6answers
210k 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 ...
138
votes
4answers
114k 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 /proc/self/...
122
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7answers
336k views

Sorting down processes by memory usage

I am able to see the list of all the processes and the memory via ps aux and going through the VSZ and RSS Is there a way to sort down the output of this command by the descending order on RSS ...
116
votes
6answers
120k views

How do I determine the number 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?
90
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6answers
84k 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?
89
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13answers
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Do I need swap space if I have more than enough amount of RAM?

From what I understand, the purpose of a swap partition in Linux is to free up some "not as frequently accessed" information from RAM and move it to a specific partition on your harddrive (at the cost ...
85
votes
1answer
88k views

How does the OOM killer decide which process to kill first?

This answer explains the actions taken by the kernel when an OOM situation is encountered based on the value of sysctl vm.overcommit_memory. When overcommit_memory is set to 0 or 1, overcommit is ...
82
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7answers
295k 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 :)
67
votes
8answers
19k views

Why can't Vim open a 100 MB text file when I have 16 GB RAM?

I have a 100MB MySQL database backup file and I have trouble to open it in Vim on my Linux box that has 16G of RAM. Vim just hangs (at least unusable). This is something I don't understand. I have 16 ...
63
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2answers
30k views

Will Linux start killing my processes without asking me if memory gets short?

I was running a shell script with commands to run several memory-intensive programs (2-5 GB) back-to-back. When I went back to check on the progress of my script I was surprised to discover that some ...
60
votes
9answers
128k views

Correctly determining memory usage in Linux

I'm a bit confused on some of the results I am seeing from ps and free. On my server, this is the result of free -m [root@server ~]# free -m total used free shared ...
59
votes
1answer
61k views

Need explanation on Resident Set Size/Virtual Size

I found that pidstat would be a good tool to monitor processes. I want to calculate the average memory usage of a particular process. Here is some example output: 02:34:36 PM PID minflt/s ...
46
votes
1answer
54k views

Getting information about a process' memory usage from /proc/pid/smaps

For a given process in /proc/<pid>/smaps, for a given mapping entry what are: Shared_Clean Shared_Dirty Private_Clean Private_Dirty Is Shared_Clean + Shared_Dirty the amount of memory that is ...
45
votes
5answers
25k views

Measuring RAM usage of a program

time is a brilliant command if you want to figure out how much CPU time a given command takes. I am looking for something similar that can measure the max RAM usage of the program and any children. ...
41
votes
2answers
87k views

Debug out-of-memory with /var/log/messages

The following report is thrown in my messages log: kernel: Out of memory: Kill process 9163 (mysqld) score 511 or sacrifice child kernel: Killed process 9163, UID 27, (mysqld) total-vm:2457368kB, ...
40
votes
3answers
63k views

How to create a user with limited RAM usage?

So I have 4 GB RAM + 4GB swap. I want to create a user with limited ram and swap: 3 GB RAM and 1 GB swap. Is such thing possible? Is it possible to start applications with limited RAM and swap ...
40
votes
4answers
32k views

grep: memory exhausted

I was doing a very simple search: grep -R Milledgeville ~/Documents And after some time this error appeared: grep: memory exhausted How can I avoid this? I have 10GB of RAM on my system and few ...
39
votes
1answer
25k views

Loading of shared libraries and RAM usage

I'm wondering about the way Linux manages shared libraries. (actually I'm talking about Maemo Fremantle, a Debian-based distro released in 2009 running on 256MB RAM). Let's assume we have two ...
38
votes
6answers
3k views

How do I use swap space for emergencies only?

I have a Debian (Buster) laptop with 8 GB RAM and 16GB swap. I'm running a very long running task. This means my laptop has been left on for the past six days while it churns through. While doing ...
38
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4answers
55k views

how is page size determined in virtual address space?

Linux uses a virtual memory system where all of the addresses are virtual addresses and not physical addresses. These virtual addresses are converted into physical addresses by the processor. To ...
37
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7answers
34k views

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

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> Is ...
34
votes
3answers
9k views

What does the vm.swappiness parameter really control?

Per the kernel documentation: This control is used to define how aggressive the kernel will swap memory pages. Higher values will increase aggressiveness, lower values decrease the amount of swap. ...
34
votes
4answers
20k views

System hanging when it runs out of memory

I've got an eeePC 900a: it has a 8GB flash as disk and only 1GB of RAM. The Linux distribution installed on it is ArchLinux. When the system runs out of memory it becomes extremely unresponsive: it ...
32
votes
3answers
12k views

Unix command to tell how much RAM was used during program runtime? [duplicate]

Let's say I'm running a script (e.g. in Python). In order to find out how long the program took, one would run time python script1.py Is there a command which keeps track of how much RAM was used as ...
28
votes
5answers
186k views

How to check which process is using most memory

When I check free in one of Prod server it showing 70% of memory is being used: total used free shared buffers cached Mem: 164923172 141171860 23751312 ...
28
votes
5answers
84k views

How to get memory used(RAM used) using Linux command?

I am trying to retrieve memory used(RAM) in percentage using Linux commands. My cpanel shows Memory Used which I need to display on a particular webpage. From forums, I found out that correct memory ...
28
votes
5answers
4k views

Making Linux read swap back into memory

The Linux kernel swaps out most pages from memory when I run an application that uses most of the 16GB of physical memory. After the application finishes, every action (typing commands, switching ...
27
votes
2answers
24k views

How to blacklist a correct bad RAM sector according to MemTest86+ error indication?

MemTest86+ (the version included with Ubuntu 13.04) says Failing address: 002f796c48 - 759.5 MB What should I specify in the memmap kernel parameter to bypass this area? I've tried running ...
27
votes
1answer
37k views

What is maximum RAM supportable by Linux?

What is the maximum supportable RAM by Linux? Assume that hardware is/supports 64-bit. Among all Linux distros. Does it go up to 16 exabytes, or is it limited like with Windows which I believe is 192 ...
26
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2answers
5k views

Is it possible to trigger OOM-killer on forced swapping?

Is it possible to have the system preemptively swap out inactive pages (vm.swappiness), but invoke the oom-killer when the system runs out of RAM (as opposed to running out of memory) and is forced to ...
24
votes
7answers
9k 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 ...
23
votes
3answers
8k views

Are files opened by processes loaded into RAM?

Commands, for instance sed, are programs and programs are codified logic inside a file and these files are somewhere on the hard disk. However when commands are being run, a copy of their files from ...
23
votes
4answers
36k views

How can I reserve a block of memory from the Linux kernel?

I have a device that needs a block of memory that is reserved solely for it, without the OS intervening. Is there any way to tell BIOS or the OS that a block of memory is reserved, and it must not ...
22
votes
1answer
15k views

getrusage system call: what is “maximum resident set size”

man getrusage 2 says ru_maxrss (since Linux 2.6.32) This is the maximum resident set size used (in kilobytes). For RUSAGE_CHILDREN, this is the resident set size of the largest ...
22
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3answers
30k views

How to reduce ClamAV memory usage?

I'm running a Ubuntu based web server (Apache, MySQL) on a 512MB VPS. This is more than sufficient for the website it is running (small forum). As I wanted to add some protection against viruses I ...
21
votes
3answers
29k views

What do the “buff/cache” and “avail mem” fields in top mean?

Within the output of top, there are two fields, marked "buff/cache" and "avail Mem" in the memory and swap usage lines: What do these two fields mean? I've tried Googling them, but the results only ...
20
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4answers
15k 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 ...
20
votes
4answers
7k views

Suspend/resume single process to/from disk

On occasion, we would like to suspend memory-intensive processes on our Ubuntu and OS X servers to temporarily free up some RAM for other jobs. If all we were worried about was CPU usage, a simple ...
19
votes
1answer
17k views

What do the different memory counters in FreeBSD mean?

top tells me: last pid: 64807; load averages: 0.99, 0.97, 0.92 up 189+04:47:22 09:16:17 45 processes: 1 running, 44 sleeping CPU: 0.4% user, 0.0% nice, ...
19
votes
1answer
13k 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 ...
19
votes
1answer
23k views

How can I test the RAM for data corruption on an ARM-based system?

I have an embedded device. It is ARM based, with Linux 2.6.31 and has 256 MB RAM. I wanted to get some ideas/tips on what is the most effective way to test the device RAM for data corruptions. Is ...
18
votes
2answers
3k 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 ...
18
votes
3answers
103k 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 | ...
18
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3answers
67k views

How to dump memory image from linux system?

I know to dump memory images in Windows. (eg-dumpit) But I don't know how to dump memory images in Linux. I want to get memory images in Linux and from Linux to Linux with ssh connection or something....
17
votes
6answers
18k 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?
17
votes
3answers
15k 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 ...
17
votes
3answers
7k 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: ...