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I have a node.js process running on a Solaris box. In the top command view, the "RES" column which I guess represents the physical memory is constant and reasonable. However the "SIZE" column keeps growing, within two hours it could reach up to 520MB and is constantly going up.

  • What does the "SIZE" column exactly represent?
  • Is this behavior acceptable (normal).
  • Would restarting the process have any effect on performance (e.g. loose cached resources, etc.) ?
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up vote 4 down vote accepted

The "SIZE" column measures the usage of address space, which is virtual memory. It's not a scarce resource, so 'excessive' consumption is usually nothing to worry about.

However, if it is constantly going up, that could indicate a memory leak. Physical memory is likely not being wasted because the memory is not being used, but if the memory is dirtied, swap space will be wasted and eventually the machine will need to do I/O to save the memory in order to keep sufficient free physical memory.

Given that you don't see the resident set size growing, I would say most likely it's not being dirtied and is simply use of address space. That, by itself, is not a cause for concern.

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Its at 2.5 GB now, looks like its going to infinity. However everything seems stable and performance is great. Thanks. – Amjad Masad Sep 22 '11 at 0:13
It does seem that something is leaking address space then. On a 64-bit OS, it can take an awfully long time for that to do damage. But going to infinity is not good. See if the rate of increase seems to be leveling off. – David Schwartz Sep 22 '11 at 0:28

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