HAMMER lockup

Matthew Dillon dillon at apollo.backplane.com
Sun Jun 29 17:05:12 PDT 2008

:I've backed up my /home partition and formatted it as HAMMER. I
:restored it and then moved some files around, did a prune-everything
:and a reblock, all worked fine. (I love to see how hammer does NOT
:stress the harddrive, as the LED rarely blinks. ;-)
:However, 256M of RAM is not enough for HAMMER, but that's not a big
:issue compared to ZFS.)
:But then I tried to stress-test by downloading
:torrents and it caused a lockup. I could do nothing but reboot,
:afterwards the UNDO was re-run and all worked fine. I can reproduce it
:just by downloading with rtorrent.
:All I could obtain is some kernel messages:
:found disconnected inode 000000010411441e
:[diagnostic] cache_lock: blocked on 0xc1529aa8 "log.smbd"
:log.smbd is strangely on a UFS partition.
:I know this is hard to debug but posted here as maybe we can sort it out
:anyway. I am glad to provide the information you need and perform the
:necessary tests as there is no sensitive data on this rig.
:Gergo Szakal MD <bastyaelvtars at gmail.com>

    You can ignore the cache_lock messages, typically.

    The disconnected inode message is for something 'hammer prune' does not
    yet deal with, but it should be harmless.  Disconnected inodes occur
    if you crash or reboot while the kernel is holding open file descriptors
    on removed files.

    The lockup is another issue.  I am currently able to lock my own test
    system up after a few hours of testing under extreme load.  I fixed
    a buffer leaks yesterday and I'll go ahead and commit what I've got
    fixed today so far, but there is still an issue somewhere.  I hope
    to find it soon.

    I would like to try to duplicate your stress test.  I will drop my
    test box down to 256M of ram but can you give me some idea on the
    torrent test you are doing?  I want HAMMER to work reliably regardless
    of the load down to 64-128M of system ram.

					Matthew Dillon 
					<dillon at backplane.com>

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