From: Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 2/2] dax: move writeback calls into the filesystems
Date: Mon, 8 Feb 2016 14:05:34 -0800
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Cc: Dave Chinner <david@fromorbit.com>, Ross Zwisler <ross.zwisler@linux.intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "Theodore Ts'o" <tytso@mit.edu>,
	Alexander Viro <viro@zeniv.linux.org.uk>, Andreas Dilger <adilger.kernel@dilger.ca>,
	Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.com>,
	Matthew Wilcox <willy@linux.intel.com>, linux-ext4 <linux-ext4@vger.kernel.org>,
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To: Jeff Moyer <jmoyer@redhat.com>
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On Mon, Feb 8, 2016 at 12:58 PM, Jeff Moyer <jmoyer@redhat.com> wrote:
> Dan Williams <dan.j.williams@intel.com> 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.

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