Nasty state after running out of swap

[Mikhail T.]

In my absence my desktop managed to run out of memory and had to kill a 
number of processes:

    pid 47493 (firefox), uid 105, was killed: out of swap space
    pid 1665 (thunderbird), uid 105, was killed: out of swap space
    pid 975 (kdeinit4), uid 105, was killed: out of swap space
    pid 1344 (mysqld), uid 105, was killed: out of swap space
    pid 898 (Xorg), uid 0, was killed: out of swap space
    pid 1430 (pidgin), uid 105, was killed: out of swap space

While that's unfortunate in its own right, the current state of the 
machine is just weird... After the massacre the swap-usage is down to 5% 
and memory is plentiful. top(1) reports:

    last pid: 85719;  load averages:  0.17,  0.15, 0.11     up
    25+21:17:34  16:50:27
    123 processes: 1 running, 102 sleeping, 11 stopped, 8 zombie, 1 waiting
    CPU:  0.1% user,  0.0% nice,  1.8% system,  0.3% interrupt, 97.7% idle
    Mem: 17M Active, 7276K Inact, 9876M Wired, 10M Cache, 1032M Buf, 28M
    Free
    ARC: 1114M Total, 264M MFU, 282M MRU, 69K Anon, 44M Header, 524M Other
    Swap: 12G Total, 616M Used, 11G Free, 5% Inuse

And yet, various commands hang for a while in either pfault or zombie 
state upon completion. For example, top, when I tried to exit it, hung 
for about a minute with Ctrl-T reporting:

    load: 0.13  cmd: top 85718 [pfault] 19.04r 0.00u 0.01s 0% 2532k

Why would a machine with so much free memory continue to act this way? 
Is it yet to recover from the "out of swap" situation? I'm sure, a 
reboot will fix everything, but I expected FreeBSD to be better than 
that... Running 10.3-stable from April 18 here. Thanks!

    -mi