Re: [PATCH 2/3] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILEflags
From: John Stultz
Date: Mon Apr 30 2012 - 17:07:49 EST
On 04/27/2012 06:36 PM, Dave Chinner wrote:
That's my concern - that persistent filesystems will have different
behaviour to in-memory filesystems. They *must* be consistent in
behaviour w.r.t. to stale data exposure, otherwise we are in a world
of pain when applications start to use this. Quite frankly, I don't
care about performance of VOLATILE ranges, but I care greatly
about ensuring filesystems don't expose stale data to user
applications....
I think we're in agreement with the rest of this email, but I do want to
stress that the performance of volatile ranges will become more
ciritical, as in order for folks to effectively use them, they need to
be able to mark and unmark ranges any time they're not using the data.
No application likely wants their data to be purged, but by volunteering
it allows them to help the kernel with low-memory constraints and
improve entire system behavior.
So if the overhead is too great for marking and unmarking pages,
applications will be less likely to "help out". :)
thanks
-john
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