Swap space is an area of the hard disk that serves as an overflow when the computer memory is full. The memory used by inactive applications is partially written out to disk to make room for other applications and for the disk cache for active files.

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Resize XFS home directory in LVM

I am desperately trying to increase the swap space available to my server from 4GB to 16GB, however at present XFS + something is making this impossible. I have a single SSD hosting the OS (CentOS 7),...
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1answer
110 views

Page cache elimination in Linux kernel

Optimizing the page cache space for less memory utilization in some system where systems don't have swap space and external flash drive or hard disk. Is there any possibility that if we can remove or ...
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1answer
2k views

How do I increase the maximum swap space on Mac OS X? [closed]

On Mac OS X Yosemite 10.10.5, when I try to run a calculation that needs to allocate and use 128 GB of memory (it is a command line program written in C), the kernel kills my process with extreme ...
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1answer
62 views

Expand the size of swap partition

I did some partition size expansions of my centOs system and recover boot loader and file system successfully.I also changed the location and expanded the swap (5GB to 8GB) partition along with above ...
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81 views

Fixing fstab after reformatting swap

I just made a small mistake and reformatted my swap partition. It's still formatted as a swap partition - I was fortunate not to touch anything more important. However, I notice that the uuid has ...
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2answers
198 views

On page fault, how does Unix determine if the faulting address is in swap space?

When a page fault occurs for a virtual address for any process how does the linux/unix operating system determine whether that page (of that virtual address) was swapped previously present in memory ...
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1answer
53 views

Cached Memory but swap is being used [duplicate]

I've got a VM with 16gb of memory and recently it's been using some of the swap space. At first I thought this was because it was using all the memory but then I read some articles about the Cached ...
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1answer
95 views

How does mkswap work? What is in the swap header it creates?

I am looking at mkswap and trying to understand how exactly it works. From what I understand, it sets up Swap space on a partition by creating a swap header. How large is this swap header? Is it one ...
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1answer
561 views

Is it safe to delete all swap partitions?

More explicitly: If it safe to shutdown a system, boot from a live cd, delete all disk swap partitions, and boot the system? This is in follow up to How to safely turn off swap permanently? (on ...
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1answer
163 views

How low can I go on RAM?

I have some old PCs runnning on my business. And by old I mean PENTIUM-3 800 MHZ and AMD DURON 950 MHZ, with 256MB RAM. They are running my business software today on Windows XP. I want to run Linux ...
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1answer
295 views

Permanent swapping with lots of free memory

We have a Linux server running Debian 4.0.5 (Kernel 4.0.0-2) with 32G RAM installed and 16G Swap configured. The system uses lxc containers for compartmentalisation, but that shouldn't matter here. ...
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How to safely turn off swap permanently? (on Debian Jessie)

I fresh installed Debian Jessie with default partitioning on an SSD drive. My current disk partitions look like this: As I have 16GB RAM, I think I don't need swap. On Windows, I had it turned off ...
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Is clearing a full swap necessary / wise?

We have a linux machine, in which the swap partition gets filled to the limit from time to time. There's still enough of RAM free, so there should be no risk of running out of memory. The usual course ...
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1answer
43 views

How to prevent swapping on Mac OS X?

I am inclined to run Tails through a virtual machine so that I could chain two VPNs. One running through the host Mac osx and one more running from inside the virtual machine that's running Tails. ...
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1answer
95 views

Zeroing out FreeBSD swap space?

I'd like to zero-fill the partitions/slices in my FreeBSD VMs in order to provide for better compression for archival. For those partitions/slices with file systems the process is no problem for me to ...
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4answers
840 views

8G RAM and SSD - how big should the swap be?

I have a computer with 8G RAM and a 128G SSD. I don't plan hibernating. What swap size would you recommend? Would you change any swappiness? In the nearest future I'll compile programs (or even ...
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1answer
32 views

Old Xen Installation Unable to be Formatted

I recently tried to format a disk that had an old Ubuntu 14.04 partition and a Xen Swap Disk partition. I am currently running the Ubuntu Live CD and trying to access my partitions on the drive for ...
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3answers
518 views

Linux, SSD and swap

This article suggests not to create a swap space on an SSD drive in order to reduce its wear. On the other hand, it suggested here that swap space positively affects performance. Would it be a better ...
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2answers
266 views

Is there way to force Linux to unswap when there is low CPU usage?

After working more than 1 day on my machine swap becomes about 1GB. Some of my panel plugins go to swap so they become laggy. Moreover system doesn't unswap until I make it to do it swapoff -all;...
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1answer
94 views

How to create Swap from already created mount points

I have prepared a CentOS 6.5 with all mount points at formatting time, including swap. Now, when I am trying to run command swapon, it shows 0 0 0. And when I am trying to create it again using mkswap,...
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FreeBSD shared swap partition with Linux

What must I do, to run these commands before Arch Linux calls swapon -a? mkswap /dev/sdaX swapon /dev/sdaX Just in case it matters, /dev/sdaX was created in FreeBSD 10.1 environment, as soon as ...
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1answer
76 views

Linux Swap Space

I have 32GB memory. SSD and NonSSD drives. I installed Linux to NonSSD drive but I prefer SSD for /var directory and I didn't create swap space because there is high memory. I know physical memory +...
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2answers
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Swap on tmpfs (Obviously a bad idea, but is it possible?)

This question originated with a joke between co-workers about increasing performance by moving swap partitions to a tmpfs. Clearly even if this is possible, it's not a good idea. All I want to know is,...
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1answer
160 views

How to calculate Swap warning/critical dynamically through script?

I have used SAR in my below script and is trying to run on individual servers for my nagios monitoring. Can someone please suggest how i can get the swap warning and swap critical values in my check ...
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1answer
121 views

Encrypted filesystems with swap partitions

A common error that happens with Ubuntu, though not Ubuntu in particular is the options of being able to encrypt the file system at installation time which creates an encrypted swap partition with ...
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1answer
96 views

Swap suddenly vanished from Debian?

Everything has been going fine for 6 months now until my swap suddenly vanished today. Now that I look into it, I find that my disk partitioning is a bit weird. What happened to it, and what should I ...
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What is kswapd_low_wmark_hit_quickly from /proc/vmstat

What does this parameter mean? # cat /proc/vmstat | grep low kswapd_low_wmark_hit_quickly 2
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1answer
79 views

swapon command is not listing the lvm name

I am facing issues with swapon -s command. It is displaying some other filename instead of my lvm name which i have given ( swap is LVM partition ) swapon -s command is not listing my LVM Name for my ...
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1answer
713 views

Why and how is swap improving performance, and can I disable it? [closed]

I have a laptop with 8GB of RAM running 4.0.4-2-ARCH. Recently, I installed Android Studio, and bam, my normally pristine system was suddenly stuttering and all out freezing (more than once). Before ...
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1answer
126 views

How to add 100MB of swap space as a logical volume in CentOS?

I need to add 100MB of swap space to my machine. I was trying to use a logical volume. # lvcreate –name lv_swap2 –size 100M vg # mkswap /dev/vg/lv_swap2 # swapon /dev/vg/lv_swap2 # vi /etc/fstab /dev/...
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1answer
177 views

Linux doesn't drop FS Caches. Instead Memory starts Swapping

I'm quite confused about this behaviour of linux memory caching. total used free shared buffers cached Mem: 15953 14188 1765 64 ...
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1answer
325 views

What happens when a tmpfs volume is full and swap is full? Is Linux's OOM-killer involved? [duplicate]

I understand that if a persistent / disk-based volume is full, files need to be explicitly deleted to free up space before more can be added. Further, I understand that if memory is exhausted, the ...
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1answer
861 views

What sets the size of tmpfs? What happens when its full?

What sets the size of the tmpfs? (On my machine it resides in /dev/shm) I can see its entry in /etc/fstab, but no notation of its size. When checking with df -h, it seems to be half the size of the ...
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how to check what is in swap?

On my system i have some amount of swap used: undefine@uml:~$ free total used free shared buffers cached Mem: 16109684 15848264 261420 633496 ...
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1answer
108 views

SWAP write protection on SSD

When using SWAP on an SSD, does the filesystem offer any write-cycle protection? i.e. randomizing or otherwise managing writes to avoid "flash wear-out" since modern SSDs are generally rated in the ...
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0answers
37 views

Which parts of Memory can Swap Support

For this question, "swap" does not include RAM and only refers to the configured space on the disk. According to, http://www.ualberta.ca/CNS/RESEARCH/LinuxClusters/mem.html, a program's memory usage ...
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1answer
97 views

Can swap space accomodate single process?

From what I understand, the swap space can be used to swap out inactive processes to free up memory. But can a single process take advantage of swap space? For example, if my system has little memory, ...
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2answers
66 views

Swap output in last x minutes

Is there any command or script to give o/p as " swap used in last 10 minutes is x" ? I wished to use that out put for my nagios monitoring.. I have used SAR in my below script and is trying to run on ...
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0answers
265 views

Ubuntu 14.04 using 100% swap space, with more than 40GB free memory, why?

I'm a bit at a loss trying to figure out why this would be the case. Can anyone provide some helpful ideas on troubleshooting this? $ free -m total used free shared ...
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1answer
184 views

Will SSD swap improve performance?

I am wondering if i have only 4GB ram and somehow(virtualbox,browser) isn't enough and i cannot proceed to upgrade(due to ultrabook and soldered memory) will swap held in SSD help the overall ...
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449 views

VGEXTEND: How to avoid wiping a swap signature in /dev/sda3?

The problem: [root@195623 ~]# vgs VG #PV #LV #SN Attr VSize VFree fedora_195623 1 3 0 wz--n- 9,50g 0 [root@195623 ~]# vgextend fedora_195623 /dev/sda3 WARNING: swap ...
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1answer
105 views

How are the values represented with the “free” command

I am interested in the totals of the 3 lines. Specifcally, if the "used" values can be counted as what's going on in real time, or if that's just a running total since the OS was started? How does ...
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4answers
2k 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 ...
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0answers
141 views

Out of Memory with unused memory and swap

I have a strange error on my Raspberry Pi2. System is archlinuxarm. Short after boot (about 30 secs), the system states that it is out of memory, resulting in closing many applications, most time ...
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1answer
331 views

Process Being Killed due to low swap

I'm running a python (2.7) script on mac osx yosemite. The script is fairly computationally intensive, certainly bumping up against my machine's RAM limitations. The computer crashes and restarts ...
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2answers
115 views

Free up swap space all at once after swap event

I use my Linux box for a lot of computational work, and sometimes a particular computation eats a lot of RAM. When I'm done, I end up with a bunch of swap used and a bunch of free memory, and if I go ...
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1answer
532 views

Is there any relationship between memory fragmentation and whether or not swap is enabled on a system?

One of the answers to Do I need swap space if I have more than enough amount of RAM? got me wondering if there is any relationship between memory fragmentation as measured by cat /proc/buddyinfo and ...
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3answers
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Is swapping enabled by default on common operating systems?

As a result of this question, I was a bit confused. After some research I found that swapping is enabled by default on Mac OS X. Swapping was furthermore introduced in Windows 3.0, so I believe it is ...
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12answers
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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 ...
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1answer
2k views

How to find the swap uuid

I am in the process of setting up a raid. sda was used during the installation and I just copied the partition table of sda to sdb like so: $ sudo sfdisk -dL /dev/sda > partition_table_sda $ sudo ...