FreeBSD 10.0 swap behavior

[rudelgurke]

Hello,
after doing an upgrade from 9.1 to 10.0 the swap behavior changed. On the 9.1 processes more or less never got swapped. After doing the upgrade to 10.0, recompiling all ports the system starts to swap processes keeping the overall swap usage around 50%.
Both with a GENERIC kernel a self-compiled one. Additional sysctl variables haven't been set so I'm asking if that is expected or not. So far didn't found much related to this in the release notes for 9.2 and 10.0.
The attached graph starts while being on 9.1, then continues with 10.0 and the change in swap usage.

 

[trh411]

In my experience, FreeBSD-10.0-RELEASE swaps for very large builds (e.g., www/chromium, www/firefox, lang/gcc, emulators/virtualbox-ose) and I'll see the swap usage go to about 15% of my 4 GB swap partition. Otherwise, it never uses swap at all. My system has 6 GB of RAM.

I went from FreeBSD-9.2 using UFS exclusively to FreeBSD-10.0 using ZFS exclusively. The ZFS ARC uses quite a bit of RAM and so I see more swapping on FreeBSD-10.0 than with FreeBSD-9.2, but as I said above, only for large builds. I have no anecdotal info to share for swap using the same underlying filesystem on both FreeBSD versions performing the same tasks.