[wplug-bsd] Frequent page faults -- getting on my nerves
Bill Moran
wmoran at potentialtech.com
Tue Apr 12 08:33:38 EDT 2005
Brandon Kuczenski <brandon at 301south.net> wrote:
> I've been running freeBSD 4.10 ("stable") since around August 1. My
> longest uptime is about 30 days. Every time there is a crash due to a
> page fault by a process associated with httpd. At the time of the last
> crash, about an hour ago, apache was version 2.0.52_3. I've since
> upgraded to the latest: 2.0.53_1, but in every case in the past, upgrading
> has not made the problem go away.
>
> The error is always the same: "Fatal trap 12: page fault while in kernel
> mode" and the current process is always httpd. I would have suspected
> hardware except that this has happened 5 times now and httpd has always
> been the current process.
>
> My httpd.conf is nothing if not unremarkable -- I think I'm using the
> defaults for pretty much everything. The only notable thing I can think
> of is that /usr/local/www/html is a symlink to /usr/local/www/data-dist,
> which I don't know if that's conventional or not.
>
> Here's a sample of the entry in /var/log/messages:
>
> Apr 11 20:06:14 ocean /kernel:
> Apr 11 20:06:14 ocean /kernel:
> Apr 11 20:06:14 ocean /kernel: Fatal trap 12: page fault while in kernel mode
> Apr 11 20:06:14 ocean /kernel: fault virtual address = 0x0
> Apr 11 20:06:14 ocean /kernel: fault code = supervisor read, page not present
> Apr 11 20:06:14 ocean /kernel: instruction pointer = 0x8:0xc169ba17
> Apr 11 20:06:14 ocean /kernel: stack pointer = 0x10:0xd1907c34
> Apr 11 20:06:14 ocean /kernel: frame pointer = 0x10:0xd1907c64
> Apr 11 20:06:14 ocean /kernel: code segment = base 0x0, limit 0xfffff, type 0x1b
> Apr 11 20:06:14 ocean /kernel: = DPL 0, pres 1, def32 1, gran 1
> Apr 11 20:06:14 ocean /kernel: processor eflags = interrupt enabled, resume, IOPL = 0
> Apr 11 20:06:14 ocean /kernel: current process = 188 (httpd)
> Apr 11 20:06:14 ocean /kernel: interrupt mask =
> Apr 11 20:06:14 ocean /kernel: trap number = 12
> Apr 11 20:06:14 ocean /kernel: panic: page fault
> Apr 11 20:06:14 ocean /kernel:
> Apr 11 20:06:14 ocean /kernel: syncing disks... 6
> Apr 11 20:06:14 ocean /kernel: done
> Apr 11 20:06:14 ocean /kernel: Uptime: 8d22h56m44s
> Apr 11 20:06:14 ocean /kernel: Automatic reboot in 15 seconds - press a key on the console to abort
> .....
>
> The only remarkable thing in httpd-error.log is a whole bunch of requests
> for mp3 files that once existed (but have since been removed) just before
> the crash. I seem to remember that this is consistent with behavior
> around the other page faults too.
>
> Is this something for the httpd list? How do I go about finding more
> information?
If this is happening this often, you can debug the kernel.
First, subscribe to one of the FreeBSD developer lists. Then update to the
current 4.x-STABLE (4.10 has been superceded by 4.11). Then, follow the
instructions below to set up your system to debug the problem:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html
Report your findings to the developers, and (hopefully) the problem will be
tracked down and fixed.
--
Bill Moran
Potential Technologies
http://www.potentialtech.com
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