HAMMER lockup

Matthew Dillon dillon at apollo.backplane.com
Mon Jun 30 09:20:57 PDT 2008

:Is there/ will there be in the future, a tunable that limits HAMMER's  
:buffer allocations ???
:I.e. can I tell HAMMER to only use a certain amount of memory and
:let me fill up the rest of available RAM as I please.
:Kaiser Jasse -- Authorized Stealth Oracle

    What tunables there are only exist to prevent HAMMER from deadlocking
    the system by running the kernel out of memory.  There is
    vfs.hammer.limit_recs which limits the number of small record
    structures HAMMER will allocate (so the M_HAMMER kmalloc pool is not
    exhausted), and vfs.hammer.limit.dirtybufspace which limits the number
    of buffers HAMMER is allowed to hold in a locked state, so HAMMER
    knows when it must do a partial finalization of UNDO data to the

    HAMMER actually slaves off of the kernel's own buffer cache buffer
    management code, so the kernel decides when HAMMER buffers must be
    freed, not HAMMER.  All the normal kernel and VM tunables apply.

					Matthew Dillon 
					<dillon at backplane.com>

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