Solved FreeBSD Browser Performance

Hello Forums,

i'm using Firefox 54 on FreeBSD 11.1-RELEASE from the pkg quarterly branch on i3wm.

I noticed when visiting big, busy websites that FF seems to do quite a lot disk IO when scrolling from top to bottom, which results in very unresponsive behaviour, e.g. cPgUp/PgDn or Home/End on a busy website takes multiple seconds while top -m io shows FF doing most of the IO while the TOTAL consists mainly of page faults.

The same system (Thinkpad x230) works as expected (no lag at all) with FF on i3wm with e.g. Arch Linux.

I just noticed the same behaviour with other (chromium) browsers too, on FreeBSD 11.1 massive IO with lagging composition, under Linux (Debian, Arch) smooth and instant composition under very similar circumstances..

Any Ideas?
I noticed that on a completely fresh installation, Firefox doesn't exhibit this behaviour on/after it's first start, but only the first start. Closing Firefox and restarting it, the lagging starts with 1-3 seconds between keyboard input. Disabling browser.cache.disk.enable appears to doesn't have any effect.

If someone want to give this a try: This happens while browsing e.g. Twitter or on "" the effect is really noticable. Or even these forums, for that matter..
I found that FF and Chromium appear to do many read/writes to /tmp/org.chromium.* and the problem seems to be related to a "missing" /dev/shm on FreeBSD.

Could this be the issue here, is the issue known already, or am i missing something here?

EDIT: well, mounting a tmpfs under /tmp indeed seems to appease the issue..