2013-12-05 22:47:53

by jon ernst

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Subject: difference between xip and o_direct.

Hi,
I am trying to understand difference between xip and o_direct.

For XIP, document xip.txt says
"instead of keeping
data in the page cache, the need to have a page cache copy is eliminated
completely. With execute-in-place, read&write type operations are performed
directly from/to the memory backed storage device."

For O_Direct,

" File I/O is done directly to/from user-
space buffers. " from manual of open(2)

So, are those 2 trying to do the same thing ? The difference I can
tell is, XIP option can be used when mounting fs. O_Direct is used in
open system-call.
Can anybody kindly teach me what are other differences?

thank you!

Jon