top/ps: is Active Memory = sum(resident set size)?

Chuck Swiger cswiger at
Tue Jan 12 17:46:51 UTC 2010


On Jan 12, 2010, at 6:17 AM, Anton Shterenlikht wrote:
> Should the Active memory, as reported by top(1), be equal to the
> sum of rss (the real memory (resident set) size of the process)
> of all processes, as reported by ps(1)?

No.  They aren't measuring the same thing; in a system with plenty of available RAM, processes might be entirely resident because there is no memory pressure to start paging inactive pages out, but only be using a fraction of their address space, in which case active per top will be less than the sum of RSS.


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