Re: 2.6.12.2 dies after 24 hours

[Chris Mason <mason@suse.com>]

On Tuesday 12 July 2005 20:27, Rob Mueller wrote:
> > > We're also applying the attached patch.  There's a bug in reiserfs that
> > > gets tickled by our huge MMAP usage (it's amazing what really busy
> > > Cyrus daemons can do to a server, ouch).  It's fixed in generic_write,
> > > so we take the few percent performance hit for something that doesn't
> > > break!
> >
> > Interesting - When I got the problem it was on mail servers under high
> > load (handling 60.000 emails pr. hour) with reiserfs as file system. I
> > have seen this problem on 5 different servers so I am confident that
> > it is not hardware failure.
> >
> > Sometimes the server load just rises and then the server dies other
> > times the load rises but the kernel manages to get it back alive
> > filling up syslog with messages like this
>
> Sounds like a different issue. The patch Bron included before fixes (or at
> least reduces to the point where it fixes it for us) a problem where
> processes get stuck in D state and are unkillable. A reboot is required to
> remove them. Apparently this is a known bug in ReiserFS (see messages
> below). As noted, the same bug exists in ext3. There appears to have been
> some patches to try and fix it for both reiserfs and ext3, but I'm not sure
> if they're in the mainline kernel yet.
>
> http://www.ussg.iu.edu/hypermail/linux/kernel/0409.0/2056.html
> http://hulllug.principalhosting.net/archive/index.php/t-22774.html
>

There is a much less complex solution that I've just recently gotten working 
in the SUSE kernel.  If reiser3/ext3 don't log the inode during atime 
updates, the problem goes away.

You can solve this now by mounting with -o noatime (although that might not 
play well with cyrus, not sure).  My current patch works around this in ugly 
ways, what I plan on doing during OLS is finding out why ext3 is still 
logging the inode all the time.

For reiser3, this was to avoid kswapd having to log a bunch of inodes in 
response to memory pressure, but that was back in 2.4 when things were 
different.  We shouldn't need to do it anymore...

-chris
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