Swap_pager and modified after free console messages

Hi,

First, apologies I dont have any extra information - that is partly
what my post is about. I have been getting a couple of messages I have
not seen before running -CURRENT, and wanted to ask whether there are
any steps I could take to help debugging if people think that is worth
tying.

This is what I have seen over the past few days:
1) kernel: memoery modified after free and then what appears to be a
memory address

I saw another post mentioning a console message like this that
appeared to be related to the subsequent panic, but mine hasnt caused
the machine to panic. I am not sure if this is because I have the
standard -CURRENT GENERIC kernel running (with WITNESS, INVARIANTS
still enabled), but a reply said use memgaurd to track down the issue.
How should I configure this?

2) a swap_pager message about not being able to allocate any more space.

My /usr filesystem was full (except for the last 8% reserved for root
only), and I had been doing some heavy ports tree compiling. I am just
not sure if that message is normal and that swap was REALLY 100% used
up, or whether it was indicative of something else and I should try to
replicate the issue.

Again, apologies if this post seems very sparse...I have very little
idea where to go with these things.

Thanks for your patience, Alex J Burke.