It is an extension of memory address space which is logically appended to the physical memory of a computer by the Memory Management Unit (MMU) of its processor. It is normally realized in operating systems by utilizing free disk space to implement such memory extension and may also be referred to ...

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67
votes
3answers
58k views

Meaning of the buffers/cache line in the output of free

Why does my server show total used free shared buffers cached Mem: 12286456 11715372 571084 0 81912 6545228 -/+ buffers/cache: 5088232 7198224 ...
43
votes
4answers
25k views

In Linux, what is the difference between “buffers” and “cache” reported by the free command?

This is an old question that I've seen from time to time. My understanding of it is rather limited (having read about the differences a long time ago, but the factoid(s) involved never really stuck). ...
1
vote
2answers
1k views

Linux out of memory on VPS

On my VPS (CentOS) 4GB ram (2 + 2 dynamically assigned when needed) and i have tomcat running with following options JAVA_OPTS="-Xms256m -Xmx2048m -XX:MaxPermSize=256m". Now when i try to start ...
29
votes
17answers
26k views

Caching/preloading files on Linux into RAM

I have a rather old server that has 4GB of RAM and it is pretty much serving the same files all day, but it is doing so from the hard drive while 3GBs of RAM are "free". Anyone who has ever tried ...
28
votes
5answers
21k views

swap partition vs file for performance?

What is better for performance? A partition closer to the inside of the disk will have slower access times, and we must wait for the drive to switch between the OS and swap partitions. On the other ...
7
votes
4answers
5k views

Understanding virtual memory usage > swap + physical on Linux

I have a process that is reporting in 'top' that it has 6GB of resident memory and 70GB of virtual memory allocated. The strange thing is that this particular server only has 8GB physical and 35GB of ...
7
votes
4answers
6k views

Constantly Increasing swap size in Linux and Swap space not being reclaimed?

I have a 8GB RAM linux box on which 4 tomcat servers are running. One of the them is set to 3000MB memory(jvm -Xms and -Xmx setting) and others are set to 1500MB. The swap partition is also set to ...
6
votes
3answers
25k views

How do I tell what process is causing kswapd to be in use?

I see kswapd using 100% CPU... how can I tell on which process's behalf kswapd is being used so much?