uncached user space mapping with mmap() ???

Jon Masters jonathan at jonmasters.org
Fri Mar 12 23:07:50 EST 2004

Fillod Stephane wrote:

<snip jcm being anal>

| Indeed! I should have written:
| "The bigger the mmap, the better, and the "lesser"  vma entries
| there will be."

Yes indeed. I shall try not to be such an anal pedant in future.


|>Are you somehow assuming you can have variable page sizes or will
|>necessarily be using BATs to map in large regions? If this is the case
|>then do bear in mind the fixed 4K page size on most platforms and the
|>fact that many architectures like 4xx do not have any BATs anyway.

| You're right. To have less entries in the page table, we would need
| variable page sizes, since 4xx does not have BAT. Hence my remark
| in form of question about ability of hugetlb. The answer must
| be in the archive.

I would love to look at the hugetlb stuff but have not got around to it.
FWIW I looked at your Wiki example of uncached access the other day and
will probably send an update for a generic peekpoke utility unless
someone tells me there already is one generally available.

| Thanks for the correction  :-)

Coffee does this kind of thing so I apologise if I ever seem snappy.
Robert Love must hate me by now with the list of stuff for his book!


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