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Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps)

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On Mon, 12 Sep 2016 21:06:49 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> On Mon, Sep 12, 2016 at 6:31 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
> > On Mon, 12 Sep 2016 08:01:48 -0700  
> [..]
> > That said, a noop system call is on the order of 100 cycles nowadays,
> > so rushing to implement these APIs without seeing good numbers and
> > actual users ready to go seems premature. *This* is the real reason
> > not to implement new APIs yet.  
> 
> Yes, and harvesting the current crop of low hanging performance fruit
> in the filesystem-DAX I/O path remains on the todo list.
> 
> In the meantime we're pursuing this mm api, mincore+ or whatever we
> end up with, to allow userspace to distinguish memory address ranges
> that are backed by a filesystem requiring coordination of metadata
> updates + flushes for updates, vs something like device-dax that does
> not.

Yes, that's reasonable.

Do you need page/block granularity? Do you need a way to advise/request
the fs for a particular capability? Is it enough to request and check
success? Would the capability be likely to change, and if so, how would
you notify the app asynchronously?

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Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-12 07:30 +0200
  Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) "Oliver O'Halloran" <oohall@gmail.com> - 2016-09-12 09:30 +0200
    Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-12 10:00 +0200
      Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-12 10:10 +0200
        Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-12 17:10 +0200
          Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 03:40 +0200
            Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams <dan.j.williams@intel.com> - 2016-09-13 06:10 +0200
              Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 07:50 +0200
        Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-12 23:40 +0200
          Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 04:00 +0200
            Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Christoph Hellwig <hch@infradead.org> - 2016-09-13 09:20 +0200
              Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-13 11:10 +0200
            Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-14 09:40 +0200
              Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-14 12:20 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-15 04:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-15 06:00 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-15 12:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-15 13:50 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Dave Chinner <david@fromorbit.com> - 2016-09-16 00:40 +0200
                Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in  /proc/self/smaps) Nicholas Piggin <npiggin@gmail.com> - 2016-09-16 08:00 +0200

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