Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE)

On Fri, Nov 13, 2015 at 01:45:52AM -0500, Daniel Micay wrote:

quoted

And now I am thinking if we use access bit, we could implment MADV_FREE_UNDO
easily when we need it. Maybe, that's what you want. Right?

Yes, but why the access bit instead of the dirty bit for that? It could
always be made more strict (i.e. access bit) in the future, while going
the other way won't be possible. So I think the dirty bit is really the
more conservative choice since if it turns out to be a mistake it can be
fixed without a backwards incompatible change.

Absolutely true. That's why I insist on dirty bit until now although
I didn't tell the reason. But I thought you wanted to change for using
access bit for the future, too. It seems MADV_FREE start to bloat
over and over again before knowing real problems and usecases.
It's almost same situation with volatile ranges so I really want to
stop at proper point which maintainer should decide, I hope.
Without it, we will make the feature a lot heavy by just brain storming
and then causes lots of churn in MM code without real bebenfit
It would be very painful for us.

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