[haiku-development] Reproducing system pauses.
- From: "Bruno Albuquerque" <bga@xxxxxxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Thu, 23 Jul 2009 13:55:25
I have mentioned more than once that I noticed system pauses (between 1
and 5 seconds) where during some IO intensive operations the system
would simply stop. Most of the time I can still move the mouse but
sometimes even the mouse stops. Syslog does not show anything of
interest and so far the only way I could reliably reproduce it was by
doing a svn up in the Haiku tree. It would always stop 3 or 4 times at
least for some seconds.
I decided to try to investigate it and, although I did not go very deep
yet, I already have some pointers:
1 - It does not happen with read operations. Only with write
operations.
2 - It seems to be related to memory allocations (the applications seem
to stop because they request memory and, somehow, can not get it).
3 - It happens even with virtual memory disabled but it shows more
easily with it disabled (probably related to swaping memory out).
I then procedded to find a way to be able to reproduce it in a very
noticeable way. This is how you can do it:
1 - Open ActivityMonitor. Be sure that you have views with CPU usage
and with memory usage.
2 - For a more dramatic effect, go to ActivityMonitor settings and
change update interval to 23 msecs (this is the fastets setting
possible).
3 - Open a terminal and run "dd if=/dev/zero of=zero.img bs=1024k count
=4096". Note this command will try to create a 4 Gb file on your HD, so
be sure to have enough space or tweak the parameters.
4 - While the file is being created, watch ActivityMonitor. you will
notice that, from time to time, the graphic will stop being updated.
Can some of you guys try this and let me know if you also see the
problem? I jsut want to rule out the problem is not on my specific
configuration.
Also, I ran the above with virtual memory disabled, bur it should be
even more noticeable with it enabled.
AFAIK, ActivityMonitor does not try to access the disk when rendering
the memory and cpu graphics (if it does, something is worng with it),
so the pause can not be attributed to it not being able to read
something from disk because of heavy IO.
Any thoughts?
-Bruno
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