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    SubjectRe: Reiserfs, 3 Raid1 arrays, 2.4.1 machine locks up
    Colonel wrote:

    > > There seem to be several reports of reiserfs falling over when memory is
    > > low. It seems to be undetermined if this problem is actually reiserfs
    > > or MM related, but there are other threads on this list regarding similar
    > > issues. This would explain why the same disk would work on a different
    > > machine with more memory. Any chance you could add memory to the box
    > > temporarily just to see if it helps, this may help prove if this is the
    > > problem or not.
    > >
    > >
    > > Well, I didn't happen to start the thread, but your comments may
    > > explain some "gee I wonder if it died" problems I just had with my
    > > 2.4.1-pre2+reiser test box. It only has 16M, so it's always low
    > > memory (never been a real problem in the past however). The test
    > > situation is easily repeatable for me [1]. It's a 486 wall mount, so
    > > it's easier to convert the fs than add memory, and it showed about
    > > 200k free at the time of the sluggishness. Previous 2.4.1 testing
    > > with ext2 fs didn't show any sluggishness, but I also didn't happen to
    > > run the test above either. When I come back to the office later, I'll
    > > convert the fs, repeat the test and pass on the results.
    > >
    > >
    > > [1] Since I decided to try to catch up on kernels, I had just grabbed
    > > -ac18, cd to ~linux and run "rm -r *" via an ssh connection. In a
    > > second connection, I tried a simple "dmesg" and waited over a minute
    > > for results (long enough to log in directly on the box and bring up
    > > top) followed by loading emacs for ftp transfers from,
    > > which again 'went to sleep'.
    > > -
    > If these are freezes I had them too in 2.4.1, 2.4.2-pre1 fixed it for me.
    > Really I think it was the patch in handle_mm_fault setting TASK_RUNNING.
    > /RogerL
    > Ohoh, I see that I fat-fingered the kernel version. The test box
    > kernel is 2.4.2-pre2 with Axboe's loop4 patch to the loopback fs. It
    > runs a three partition drive, a small /boot in ext2, / as reiser and
    > swap. I am verifying that the freeze is repeatable at the moment, and
    > so far I cannot cause free memory to drop to 200k and a short ice age
    > does not occur. Unless I can get that to repeat, the effort will be
    > useless... the only real difference is swap, it was not initially
    > active and now it is. Free memory never drops below 540k now, so I
    > would suspect a MM influence. didn't mention
    > the memory values in his initial post, but it would be interesting to
    > see if he simply leaves his machine alone if it recovers
    > (i.e. probable swap thrashing) and then determine if the freeze ever
    > re-occurs. James seems to have better repeatability than I do.
    > Rebooting and retrying still doesn't result in a noticable freeze for
    > me. Some other factor must have been involved that I didn't notice.
    > Still seems like MM over reiser tho.

    When the machine stopped responding, the first time, I let it go over the weekend
    (2 days+) and it still didn't recover. I never saw a thrashing effect. The
    initial memory values were 2MB free memory, < 1MB cache. I never really looked at
    the cache values as I wasn't sure how they affected the system. when the system
    was untarring my tarball, the memory usage would get down < 500kb and swap would be
    around a couple of megs usually.

    > PS for james:
    > >One thing I did notice was that the syncing of the raid 1 arrays went in
    > sequence, md0, md1, md2 instead of in parrallel. I assume it is because
    > the machine just doesn't have the horsepower, etc. or is it that I have
    > multiple raid arrays on the same drives?
    > Same drives.

    That's what I thought.


    James A. Pattie

    Linux -- SysAdmin / Programmer
    PC & Web Xperience, Inc.

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