Naive question about grant/map
kevine at cse.unsw.edu.au
Thu Dec 11 08:48:24 CET 2003
Volkmar Uhlig <mailto:volkmar at ira.uka.de> scribbled on Thursday, 11 December
2003 5:59 PM:
>> sense of the word.
> This also depends on your point of view. Your statement that the
> mapping can be a superset of user-level pagers is wrong. The
> pagers have full knowledge about the replacement policy (since it is
> implemented in user land via map and unmap) and therefore can rely on
> the fact that the kernel won't replace entries in the cache. If it
> would be a superset then the kernel would have to enter values itself.
I believe I am not wrong, just mis-interpreted :-). The superset I refer it
is where pager effective discards the information required to re-establish
the mapping after establishing it and relies on the kernel to hold the only
copy, i.e. the kernel posseses a superset of the mapping stored by the
Older versions of sigma0 (maybe the current version too) did not keep track
of mappings they handed out, only the fact that a page had been mapped. This
is a concrete example of what I meant by a superset. Only the kernel has the
actual mapping established and it was lost if a client of sigma zero flushed
I'm not arguing that it is a sensible thing to do in all but the most
controlled situations (and maybe not there as well), but it can be done.
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