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From: Nicholas Piggin <npiggin@gmail.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	Yumei Huang <yuhuang@redhat.com>, Michal Hocko <mhocko@suse.com>,
	Xiao Guangrong <guangrong.xiao@linux.intel.com>,
	KVM list <kvm@vger.kernel.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Gleb Natapov <gleb@kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
	mtosatti@redhat.com,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps)
Date: Tue, 13 Sep 2016 15:40:48 +1000	[thread overview]
Message-ID: <20160913154048.76b0e0bc@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <CAPcyv4iPh2io4S4LpyFvgn9NcoOUEHU25uBz3aSZPJaxbZJZoA@mail.gmail.com>

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?

  reply	other threads:[~2016-09-13  5:41 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-08  4:32 DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Dan Williams
2016-09-08 22:56 ` Ross Zwisler
2016-09-08 23:04   ` Dan Williams
2016-09-09  8:55     ` Xiao Guangrong
2016-09-09 15:40       ` Dan Williams
2016-09-12  6:00         ` Xiao Guangrong
2016-09-12  3:44       ` Rudoff, Andy
2016-09-12  6:31         ` Xiao Guangrong
2016-09-12  1:40   ` Dave Chinner
2016-09-15  5:55     ` Darrick J. Wong
2016-09-15  6:25       ` Dave Chinner
2016-09-12  5:27   ` Christoph Hellwig
2016-09-12  7:25     ` Oliver O'Halloran
2016-09-12  7:51       ` Christoph Hellwig
2016-09-12  8:05         ` Nicholas Piggin
2016-09-12 15:01           ` Christoph Hellwig
2016-09-13  1:31             ` Nicholas Piggin
2016-09-13  4:06               ` Dan Williams
2016-09-13  5:40                 ` Nicholas Piggin [this message]
2016-09-12 21:34           ` Dave Chinner
2016-09-13  1:53             ` Nicholas Piggin
2016-09-13  7:17               ` Christoph Hellwig
2016-09-13  9:06                 ` Nicholas Piggin
2016-09-14  7:39               ` Dave Chinner
2016-09-14 10:19                 ` Nicholas Piggin
2016-09-15  2:31                   ` Dave Chinner
2016-09-15  3:49                     ` Nicholas Piggin
2016-09-15 10:32                       ` Dave Chinner
2016-09-15 11:42                         ` Nicholas Piggin
2016-09-15 22:33                           ` Dave Chinner
2016-09-16  5:54                             ` Nicholas Piggin
2016-12-19 21:11                               ` Ross Zwisler
2016-12-20  1:09                                 ` Darrick J. Wong
2016-12-20  1:18                                   ` Dan Williams
2016-12-21  0:40                                     ` Darrick J. Wong
2016-12-21 16:53                                       ` Dan Williams
2016-12-21 21:24                                         ` Dave Chinner
2016-12-21 21:33                                           ` Dan Williams

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