Re: [PATCH 2/2] dax: move writeback calls into the filesystems

[Dan Williams]

On Mon, Feb 8, 2016 at 12:58 PM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:
> Dan Williams <dan.j.williams@xxxxxxxxx> writes:
>
>> I agree the mount option needs to die, and I fully grok the reasoning.
>>   What I'm concerned with is that a system using fully-DAX-aware
>> applications is forced to incur the overhead of maintaining *sync
>> semantics, periodic sync(2) in particular,  even if it is not relying
>> on those semantics.
>>
>> However, like I said in my other mail, we can solve that with
>> alternate interfaces to persistent memory if that becomes an issue and
>> not require that "disable *sync" capability to come through DAX.
>
> What do you envision these alternate interfaces looking like?

Well, plan-A was making DAX be explicit opt-in for applications, I
haven't thought too much about plan-B.  I expect it to be driven by
real performance numbers and application use cases once the *sync
compat work completes.