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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454
votes
9answers
680k views

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?
221
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8answers
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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 ...
189
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13answers
177k 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?
188
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8answers
259k 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 ...
157
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4answers
156k views

How do I determine the number of RAM slots in use?

I forgot how many RAM (DIMM) 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?
149
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4answers
131k 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/...
148
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8answers
387k 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 ...
113
votes
1answer
119k 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 ...
104
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7answers
96k 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?
97
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13answers
53k views

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 ...
93
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9answers
338k 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 :)
72
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2answers
38k 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 ...
69
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8answers
21k 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 ...
68
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9answers
144k 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 ...
67
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2answers
77k 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 ...
51
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1answer
59k 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 ...
49
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3answers
75k 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 ...
48
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4answers
75k 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 ...
48
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3answers
65k 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 ...
47
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5answers
30k 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. ...
47
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2answers
101k 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, ...
46
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6answers
5k 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 ...
45
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1answer
29k 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 ...
44
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5answers
256k 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 ...
44
votes
4answers
40k 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
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3answers
21k 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 ...
39
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7answers
46k 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 ...
39
votes
4answers
28k 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 ...
37
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3answers
11k 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. ...
33
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6answers
96k 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 ...
32
votes
8answers
13k 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 ...
32
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5answers
5k 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 ...
31
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1answer
42k 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 ...
30
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2answers
30k 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 ...
30
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3answers
44k 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 ...
27
votes
2answers
7k 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 ...
26
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4answers
42k 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 ...
26
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4answers
6k views

What is the gold linker?

Has anyone used the gold linker before? To link a fairly large project, I had to use this as opposed to the GNU ld, which threw up a few errors and failed to link. How is the gold linker able to link ...
26
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1answer
19k 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 ...
25
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3answers
11k 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 ...
25
votes
3answers
112k 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 | ...
23
votes
1answer
56k 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, ...
23
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4answers
8k 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 ...
22
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2answers
27k views

How to place / store a file in memory on linux?

I have read somewhere that one can put a file on a linux system into memory, and loading it will be superfast. How do I do this? How do I verify the file is loaded from memory?
21
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4answers
17k 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 ...
21
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2answers
26k 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 ...
20
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8answers
18k 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: set up a cron-job implement a loop with sleep in the script itself. Question: Which is the ...
20
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6answers
24k 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?
20
votes
1answer
19k 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, ...
20
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3answers
86k 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....

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