Some things in top's output are pretty straightforward, like memory and swap usage. But load average numbers are a bit of a mystery: what do these three numbers mean? Also, what exactly is a zombie process and how is it different from a sleeper?

top - 13:20:58 up 69 days,  7:07,  1 user,  load average: 0.03, 0.02, 0.00
Tasks:  80 total,   1 running,  79 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0% us,  0.2% sy,  0.0% ni, 99.8% id,  0.0% wa,  0.0% hi,  0.0% si
Mem:   8054888k total,  7975100k used,    79788k free,   130240k buffers
Swap:  1572856k total,       84k used,  1572772k free,  6393160k cached
  • I might suggest checking out htop as a top replacement. It has a much nicer interface.
    – baudtack
    May 12, 2009 at 18:08
  • 2
    Arrrgh, I can't edit the formatting! Browsing ServerFault is going to drive me crazy...
    – mmyers
    May 12, 2009 at 18:10

2 Answers 2


Load average reference.

Zombie process reference.


The 3 load average numbers is the load your system has been under for the past minute, 5 minutes, and 15 minutes.

I'm not exactly clear on how load is calculated - but it has something to do with how many processes are demanding cpu time at once. A server that is running consistently below 1.0 means it has no processes waiting for the cpu (ie. it is running at maximum speed)

  • 3
    The value of "1" only applies on a single CPU machine. Multiply it by the number of CPUs in the system to get your "overload limit." That is, in a four processor machine, a value equal to or less than 4.0 indicates that the machine is not overloaded.
    – Boden
    May 12, 2009 at 19:00

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