SuperPages utilization survey

[Ivan Voras]

hello,

I was wondering how much usage superpages get in real-world systems, and
made a small script to parse the output of "procstat -va":

http://people.freebsd.org/~ivoras/stuff/spsurvey.py

The results from three systems (with the script being run as root) are here:

http://people.freebsd.org/~ivoras/stuff/spsurvey_desktop.txt
http://people.freebsd.org/~ivoras/stuff/spsurvey_mixserver.txt
http://people.freebsd.org/~ivoras/stuff/spsurvey_webserver.txt

What I get from it is that they are really under-utilized, probably
because it's a rare occasion that every single page in a 2 MB region is
touched to enable its promotion.

The only good case seems to be the third one, with the database
accessing the whole memory range a lot, but the statistics which
procstat reports is inaccurate: there could be only a single superpage
in the whole region and procstat will make the region with the "S" flag.

If there's anyone else wishing to run the script and post the results,
it could be useful to see.


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