question regarding organization of the pte hash table

Dan Malek dan at
Tue Mar 26 05:37:27 EST 2002

Neil Horman wrote:

> .... use of the PPC860 MMU (my processor in question),

The MPC8xx family processors don't use a hash table.  We just use a two-level
Linux page table and fill the TLBs using the software table walk as described
in the manual.

> .... memory context (CASID) using that same

The MPC8xx identifies 16 possible ASIDs, plus a global identifier we use
in the kernel.  The sixteen ASIDs are assigned to the 16 most active memory
contexts.  If we require the use of a memory context that does not have an
ASID assigned, we invalidate one of the existing ones and claim it.

To minimize source code changes, we try to utilize as much common code as
possible.  Sometimes, the same 'hash' functions are called on processors that
don't use hash tables, because there is some TLB side effect we still want to
cause.  Anything hash table related is skipped, but the TLB management is still

	-- Dan

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