a Linux swap storm

Andries.Brouwer
2006-05-07T19:31:39Z

Earlier this evening I showed someone some pictures under X:

% display -size 300x300 *.jpg

(395 pictures, 315 MB). When display (from ImageMagick)
started to repeat, I exited the program.
At this moment the machine became unusable for twenty minutes
of solid disk activity.
No keystroke seen, not even the Ctrl-Alt-Backspace to kill X,
or Ctrl-Alt-F1 to switch consoles, no mouse movement seen,
vmstat did not produce any output for twenty minutes.

The vmstat 5 output was

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa

0 3 315728 3164 4424 3356 646 382 792 382 2425 182 0 5 0 95
1 1 316356 3856 4428 3572 454 366 507 366 2242 150 0 5 0 95
0 1 317540 3784 4456 3664 530 578 590 578 2403 179 0 7 0 93
0 1 306740 4240 4524 5372 127013 49878 129427 50061 405016 32901 0 4 0 95
1 1 306712 3992 4536 5372 30 0 30 3 450 122 2 1 94 2
0 0 306692 4016 4548 5372 18 0 18 3 402 134 2 2 96 1
0 0 306692 4016 4560 5372 0 0 0 3 257 35 1 1 98 0

The machine is vanilla 2.6.14, 256MB, 550MB swap.

% rpm -qf `which X`
xorg-x11-server-6.8.2-100

I wonder what precisely happened. Is this an X bug? Or a kernel bug?
The effect is reproducible.

Andries