My system is a 1.8 GHz Pentium using Debian stable. I update frequently from debian.org.
Several weeks ago, I started noticing that Iceweasel would sometimes
stop responding to mouse or keyboard inputs for about five seconds.
After each such "hang" it would resume operating normally.
For example, while reading a web page I would try to scroll down by
clicking on the down arrow at the bottom of the scroll bar. Nothing
would happen, so I would click once or twice again, with no response.
After a few seconds, the window would suddenly scroll to the bottom of
the page - as if responding to all the backlogged mouse clicks.
I could not identify the problem with any particular software install or
update. Of course, the problem may have been happening for weeks before
I noticed the pattern of "hangs".
After some Googling, I thought the problem might be related to Java or
Flash, so in Edit-Preferences I disabled Java, and I installed
Flashblock 5.1.11.2. This appeared to have no effect on the frequency
with which the hangs occurred.
Also I tried to identify the problem with specific web sites. I most
often had the problem on newspaper websites, e.g.
www.theglobeandmail.com, but it seemed to occur intermittently on other
sites as well. Because of the random nature of the problem I have not
been able to decide whether it occurs on all websites or just some websites.
To further isolate the problem I ran top in a Gnome terminal. To be
specific, I ran terminal, su'ed to root, then
lucy:/home/jack# nice --adjustment=-20 top
I arranged the windows so that I could use iceweasel without covering up
the terminal window, then browsed until a "hang" happened.
What this showed was that during a "hang", iceweasel (firefox-bin) was
using close to 100% of the CPU. However, this did not stop the terminal
or any other application from responding. In fact, further testing
showed that during a hang, if I was quick, I could go to another
application window, use the mouse or keyboard and get a response, then
return to iceweasel, and iceweasel would still not respond until after a
significant delay.
By going to the terminal window that had top running, and hitting ^C
during a "hang", I captured the following top output - which is typical
of what I saw during hangs:
top - 15:57:35 up 28 days, 19:23, 3 users, load average: 0.66, 0.62, 0.47
Tasks: 173 total, 3 running, 170 sleeping, 0 stopped, 0 zombie
Cpu(s): 96.7%us, 2.6%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.3%hi, 0.3%si,
0.0%st
Mem: 775980k total, 763664k used, 12316k free, 16904k buffers
Swap: 9767512k total, 118268k used, 9649244k free, 372708k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND
6895 jack 20 0 216m 125m 21m R 93.0 16.5 2:48.19
firefox-bin
6027 root 10 -10 114m 26m 7460 S 6.6 3.5 5:04.60
Xorg
7022 root 0 -20 2520 1176 884 R 0.7 0.2 0:00.10
top
1 root 20 0 2100 428 400 S 0.0 0.1 0:21.94
init
If anyone can identify this problem, or offer suggestions about how to
further narrow it down, I would appreciate it.
Jack Dodds
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