sendfile and page usage statistics

David G Lawrence dg at
Wed Oct 10 11:13:01 PDT 2007

> The read() from file certainly updates vnode pages' PG_A/PG_REFERENCED,
> because coping to userland is made by CPU. I think write() does the same.

   No, it does not. The kernel virtual mappings involved in that copy
are "special"; page bits (PG_A, PG_M, etc) from those mapping are not
preserved from the PTEs (at least not on x86).

David G. Lawrence
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