Messages in this thread | | | Date | Sun, 11 Aug 2002 15:51:22 +0100 | From | Jamie Lokier <> | Subject | Re: [patch 15/21] multiple pte pointers per pte_chain |
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Andrew Morton wrote: > Pages which are mapped by only a single process continue to not have a > pte_chain. The pointer in struct page points directly at the mapping > pte (a "PageDirect" pte pointer). Once the page is shared a pte_chain > is allocated and both the new and old pte pointers are moved into it.
May I suggest that the final pte in the list of ptes for a page is _always_ pointed to directly?
In other words, a pte_chain looks like this:
struct page -> pte_chain -> pte_chain -> pte_chain -> pte | | | v v v pte pte pte
pte_chain vs. pte would be distinguished by the least significant bit of the pointer, or something similar.
This adds a special case in the list walker -- on the other hand, it also removes two special cases ("PageDirect" is no longer required, and there is no 0 to indicate end-of-list). But the best part is: it saves more memory, has no cache line cost, and reduces the amount of work needed to share a page :-)
-- Jamie
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