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How swap space is used in Linux and Unix

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BitJam
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How swap space is used in Linux and Unix

#1

Post by BitJam » Tue Aug 13, 2019 2:47 pm

I learned a lot from this article: What has to happen with Unix virtual memory when you have no swap space

TL;DR:
1) Running out of memory with no swap will bring your system to its knees (or worse).

2) Swap is only used for memory that does not already have a copy on disk. Libraries and executables are usually available on disk and therefore don't use swap space.

3) Therefore if you are running out of memory and have no swap then the disk will still thrash as it swaps out libraries and executables that may be needed right away.
Will I cry when it's all over?
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Adrian
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Re: How swap space is used in Linux and Unix

#2

Post by Adrian » Tue Aug 13, 2019 3:55 pm

Oh, interesting didn't know about no. 3.

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manyroads
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Re: How swap space is used in Linux and Unix

#3

Post by manyroads » Tue Aug 13, 2019 6:22 pm

I have found that my swap is almost 100% idle. Could be because I have 24GB of RAM.... Anyway on all my new builds I just add RAM and ignore swap. Sloppy programmer behavior I guess. :needcoffee:
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mxer
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Re: How swap space is used in Linux and Unix

#4

Post by mxer » Wed Aug 14, 2019 4:56 am

As long as you have enough ram to cover your computer use needs, you don't need any swap, but if you do work that requires a lot of ram use, compiling big programs/intensive video work, etc, then you'd better have some. probably the equal of the amount of ram you have installed.

Me? I used to get away with no swap on a 1GB machine, but now have at least 2GB, because of how much a modern web browser wants to use. :happy:
(FOSS, Linux, & BSD since 1999)

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Richard
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Re: How swap space is used in Linux and Unix

#5

Post by Richard » Wed Aug 14, 2019 6:15 am

I use a 1 GB swap file on /media/SWAPFS of the T430, just in case. And I occasionally see a small usage.
Probably for my use even ½ GB would suffice.

I believe it has reduced some occasional lags that I noticed while running without any swap.
All subjective but it feels right.
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