Tuning Question

Lowell Gilbert freebsd-questions-local at be-well.ilk.org
Mon Feb 12 15:17:26 UTC 2007

Cy Schubert <Cy.Schubert at komquats.com> writes:

> I have a question about tuning FreeBSD systems, specifically in regard to 
> memory. At one time on Solaris systems it was recommended to keep scan rate 
> below 200 pages per second. (Today it's 300 pages per second, dependent on 
> the amount of memory, class of system.) Are there any recommendations or 
> rules of thumb a person can use to determine when a memory upgrade is 
> required? My machines are only busy during port builds when the scan rate 
> can vary greatly and the page out rate could reach as high as two pages per 
> second during brief periods. What kind of memory and paging metrics should 
> I use on FreeBSD systems?

I'm not convinced that such a simple algorithm makes sense these days.
If the system is normally pretty quiet, then it is unlikely you'll see
any difference from optimizing memory behaviour further.  

I believe that when top(1) gives memory sizes, they are in bytes
rather than pages as the manual indicates.

Lowell Gilbert, embedded/networking software engineer, Boston area

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