Thursday, July 20, 2006

Scalability prediction with sysstat

"How many users can run their applications on this machine?"

This kind of question comes up often, but determining a precise value is hard. A key metric for getting this number is the amount of memory needed by every user. Unfortunately it's difficult to find out how much memory this is, because certain pages (e.g. code, read-only data) are shared among different processes on Solaris, which is of course a Good Thing TM.

In most cases the highest impact on exclusively used memory have stack and heap. So if you are curious how much heap and stack your users are using, try sysstat. You can get it here.

I'd be happy to hear from you, if you simply like sysstat, want to report a bug, or have a proposal for an enhancement.


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