Machine unresponsive with cache_lock: blocked on... message

Francois Tigeot ftigeot at
Sat Mar 20 13:11:30 PDT 2010

On Sat, Mar 20, 2010 at 12:52:28PM -0700, Matthew Dillon wrote:
> :This machine was really fine running the same workload with 2.4.
> :
> :With 2.5, simple hammer cleanup or rsync commands are enough to make
> :PCs with 2GB or 3GB memory swap.
>     The kernel can't really tell the difference between the desire to
>     cache a lot of data and a single-scan operation such as rdist or
>     hammer cleanup (and even then it has no idea whether the rdist
>     represents a data set small enough to be cached or not).
>     So its like half dozen of this or a half dozen of that... there is
>     no right answer.  We would need something like an ARC cache for our
>     VM pages and vnodes to distinguish between the cases.

Okay. Since this is not really something which can be resolved automatically,
is there a way for the administrator to set a hard limit to the memory used
by disk activity ?
A sysctl such as kern.max_disk_cache or so ?

Francois Tigeot

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