[NCLUG] Choppy performance issues.

[John Gilmore]

This is especially showing up in minecraft. It's been years since I
played it on this machine, but it used to work just fine.

Now it updates a few(!) frames, then locks up for almost a second
before continuing. Tellingly, other apps show the same performance
issues, even ones that aren't using X at all (minecraft server running
under screen, noteably)

I used to think it was ZFS. So I copied everything to a spare disk
formatted ext3, and the problem persists. Which I kinda like, because
I didn't want to give up ZFS's features.

I tried increasing the priority of X and java to no avail. This is an
older quad core machine with 4G memory. I set top to update at 300
secs, and this is what I got:
top - 09:57:32 up 13:50,  3 users,  load average: 1.20, 1.22, 1.10
Tasks: 314 total,   1 running, 313 sleeping,   0 stopped,   0 zombie
%Cpu(s):  8.7 us, 25.7 sy,  0.0 ni, 65.4 id,  0.0 wa,  0.0 hi,  0.1 si,  0.0 st
KiB Mem:   3803424 total,  2403724 used,  1399700 free,   106848 buffers
KiB Swap: 16775164 total,        0 used, 16775164 free,   854228 cached

  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+  COMMAND
10946 jgilmore  20   0 1090m 669m  33m S 111.3 18.0  14:42.05 java
 6153 jgilmore  15  -5  160m 6476 4536 S   4.1  0.2  23:47.45 pulseaudio
10860 jgilmore  20   0  641m 175m  30m S   2.5  4.7   0:43.03 iceweasel
 4495 root      20   0 86572  48m  12m S   1.7  1.3   1:04.85 Xorg
10832 root      20   0     0    0    0 S   1.6  0.0   0:12.47 kworker/3:4


What I noticed here is 25.7%sys is suspiciously close to "one CPU is
locked somewhere in the kernel" But that's all I got.