On 13/11/15 02:03 AM, Minchan Kim wrote: > On Fri, Nov 13, 2015 at 01:45:52AM -0500, Daniel Micay wrote: >>> 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. Well, I don't think you need more than a good API and an implementation with no known bugs, kernel security concerns or backwards compatibility issues. Configuration and API extensions are something for later (i.e. land a baseline, then submit stuff like sysctl tunables). Just my take on it though...
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