On Tue, Sep 26, 2017 at 11:30:57AM -0600, Ross Zwisler wrote: > I agree that Christoph's idea about having the system intelligently adjust to > use DAX based on performance information it gathers about the underlying > persistent memory (probably via the HMAT on x86_64 systems) is interesting, > but I think we're still a ways away from that. So what are the missing blockers for a getting started? > FWIW, as my patches suggest and Jan observed I think that we should allow > users to turn on DAX by treating the inode flag and the mount flag as an 'or' > operation. i.e. you get DAX if either the mount option is specified or if the > inode flag is set, and you can continue to manipulate the per-inode flag as > you want regardless of the mount option. I think this provides maximum > flexibility of the mechanism to select DAX without enforcing policy. IFF we stick to the dax flag that's the only workable way. The only major issue I still see with that is that this allows unprivilegued users to enable DAX on a any file they own / have write access to. So there isn't really any way to effectively disable the DAX path by the sysadmin. > Does it make sense at this point to just start a "dax" man page that can > contain info about the mount options, inode flags, kernel config options, how > to get PMDs, etc? Or does this documentation need to be sprinkled around more > in existing man pages? A dax manpage would be good.
