SUMMARY: Difference between TOP and ps output

From: James M. Thompson (
Date: Sat Nov 04 1995 - 03:48:48 CST

First a clarification-I should have noted in my original question that
the example I cited was from memory and meant for illustrative purposes.
The reason I point this out is that the correct answer to my question
does not make sense if reviewed against my original posting.


> I've noticed a difference in the memory usage information returned by top
> and the ps command. For example, top shows for a process SIZE=132M and
> RES=18M, but /usr/ucb/ps -auxw reports SIZE=44038 and RSS=8095. I believe
> that the ps command does not include the text size of the program, whereas
> top does. I expect to see some difference in the returned information, but
> not of the magnitude shown above.
> Other information - top and ps returns the same value for cpu time used
> by the process. The system memory usage summary matches vmstat output.
> Bottom Line Questions:
> 1) Which command has the correct process memory usage information. If the
> answer is that both are correct because they are reporting two different
> views of memory, what are the different views?
> 2) Does top 3.3 run correctly on an MP system? (There seems to be a
> difference of opinion in my organization.)


1) TOP shows memory usage in Kilobytes and ps show memory in units of pages.
   In my case the page size is 4KB.

2) TOP 3.3 works on MP machines.

Thanks to the following people for their feedback:
David Blackman
Allen Livingston
Kevin Sheehan
Daniel Blander

Jim Thompson
phone: 703-714-3284

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