Memory

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Memory, in computing, refers to the non-persistent storage area in a computer. All the programs actively running on your computer use up some of its memory. The operating system (the kernel and any basic services it relies on) also consume memory.

Physical memory means the RAM (Random-Access Memory) installed in your computer. Virtual memory is an extension of physical memory by using the hard disk as a swap space to simulate more RAM in situations where the programs running on the system demand more memory than is actually available. Least recently used "pages" are written to the much slower disk to provide additional RAM that processes need and are read out when called for.

Find out your memory configuration

To find out how much RAM you have, enter

# hwinfo --memory
01: None 00.0: 10102 Main Memory
  [Created at memory.59]
  Unique ID: rdCR.CxwsZFjVASF
  Hardware Class: memory
  Model: "Main Memory"
  Memory Range: 0x00000000-0xc7fffffff (rw)
  Memory Size: 50 GB
  Config Status: cfg=new, avail=yes, need=no, active=unknown

In this case you have 50 GB of memory.

To find out what dimms you have, use

# dmidecode | less
Memory Device
        Array Handle: 0x1000
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
        Size: 4096 MB
        Form Factor: DIMM

Tips

  • On most Linux systems the cat /proc/meminfo command gives a static printout of current memory utilization
  • top analyzes and displays continuously updated statistics on current memory usage

related commands

  • free -- shows the free memory