Re: Determining disk activity per volume
Re: Determining disk activity per volume
- Subject: Re: Determining disk activity per volume
- From: Quinn <email@hidden>
- Date: Wed, 11 Oct 2006 18:11:02 +0100
At 13:48 +0100 11/10/06, Arvind Dalvi wrote:
wondering....if I/O Media Filter puts the application on hot path,
how are filesystem filter drivers (example: on-access antivirus
scanners) implemented ?
Mac OS X does not support file system filter drivers ("stacking file
systems" in Mac OS X terminology). See Q&A 1242 for the details.
<http://developer.apple.com/qa/qa2001/qa1242.html>
On-the-fly AV scanners are mostly implemented at the kauth level.
Kauth tells you when files are opened and closed [1], not when
individual reads and writes are done. Getting into the read/write
hot path just to gather statistics is not recommended. There are
plenty of other mechanisms. For example:
At 9:12 -0700 11/10/06, Shawn Erickson wrote:
IOBlockStorageDriver already does this and that information is
readable via the ioregistry.
And this is exactly what <x-man-page://8/iostat> does. Take a look
at the "devstats" routine in the following source file.
<http://www.opensource.apple.com/darwinsource/10.4/system_cmds-336/iostat.tproj/iostat.c>
S+E
--
Quinn "The Eskimo!" <http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
[1] Actually, that's a simplification. Some kauth operations are
actual notifications (stuff in the "file operation scope"), but
others (stuff in the "vnode scope") only occur when an operation is
authorised, and authorisations can be cached (so there's no
one-to-one correspondence between operations and kauth callback
invocations).
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