On Fri, 15 Feb 2013 01:34:50 -0500
Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
> + * The status is returned in a vector of bytes. The least significant
> + * bit of each byte is 1 if the referenced page is in memory, otherwise
> + * it is zero.
Also, this is going to be dreadfully inefficient for some obvious cases.
We could address that by returning the info in some more efficient
representation. That will be run-length encoded in some fashion.
The obvious way would be to populate an array of
struct page_status {
u32 present:1;
u32 count:31;
};
or whatever.
Another way would be to define the syscall so it returns "number of
pages present/absent starting at offset `start'". In other words, one
call to fincore() will return a single `struct page_status'. Userspace
can then walk through the file and generate the full picture, if needed.
This also gets inefficient in obvious cases, but it's not as obviously
bad?
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