Does the page fault occur while their is read request for a file that is
opened with IRP_NOCACHE.
Page fault happen when we refer to virtual address that is not backed by a
physical page. This is fine for cached IO. But if the IO is non cached then
there would not be any memory allocated to non cached file. So there is no
question(I guess) of virtual address existence in this case. since no
virtual address exist for that non cached file, then page fault should not
occur. Can some one from you validate my statements. Is I am thinking in
right direction
A page fault can occur when performing any I/O operation (including
non-cached I/O operations.) The page fault could refer to the buffer
(from the user address space,) the file system code, the file system
data (and/or meta-data.) The *only* point is that the data will
typically be placed into the buffer directly and not via the cache. I
say typically because even this is not a firm guarantee (e.g.,
compressed files in NTFS, encryption filters that need to perform the
I/O out-of-band, etc.)
The statement that you made “since no virtual address exist for that non
cached file…” doesn’t make sense to me. The MDL describes the
physical pages, but this is not to imply there are no virtual references
to those physical pages.
Tony
Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com http:</http:>
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Rohit
Sent: Wednesday, June 06, 2007 2:07 AM
To: ntfsd redirect
Subject: [ntfsd] Query regarding page faults
Does the page fault occur while their is read request for a file that is
opened with IRP_NOCACHE.
Page fault happen when we refer to virtual address that is not backed by
a physical page. This is fine for cached IO. But if the IO is non cached
then there would not be any memory allocated to non cached file. So
there is no question(I guess) of virtual address existence in this case.
since no virtual address exist for that non cached file, then page fault
should not occur. Can some one from you validate my statements. Is I am
thinking in right direction
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