HAMMER lockup

Matthew Dillon dillon at apollo.backplane.com
Sun Jun 29 17:27:37 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.)

    Yah, I like HAMMER's buffering too.  UFS's softupdates has to flush
    under certain conditions and UFS also uses cluster_write() which
    tends to want to flush data out as buffers fill up.  HAMMER doesn't
    have to flush under any circumstances until the number of dirty buffers
    exceeds 1/2 the available buffer space.

    I've never run rtorrent, what you are rtorrent'ing to cause the lockup?

    I am half suspecting that the lockup may be due to large write()'s
    occuring in parallel and deadlocking the buffer cache.  Nearly all of
    the other lockups I located during testing have been related to buffer
    cache deadlocks.  I should be able to get it fixed this evening if I
    can get it more reliably reproduced on my test box.


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