linux-kernel - Re: [PATCH v3 2/5] /dev/dax, pmem: direct access to persistent memory

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Date:	Fri, 20 May 2016 10:01:36 +0200
From:	Johannes Thumshirn <jthumshirn@...e.de>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	linux-nvdimm@...ts.01.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	linux-kernel@...r.kernel.org, hch@....de,
	linux-block@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 2/5] /dev/dax, pmem: direct access to persistent memory

On Wed, May 18, 2016 at 01:56:16PM -0700, Dan Williams wrote:
> Device DAX is the device-centric analogue of Filesystem DAX
> (CONFIG_FS_DAX).  It allows memory ranges to be allocated and mapped
> without need of an intervening file system.  Device DAX is strict,
> precise and predictable.  Specifically this interface:
> 
> 1/ Guarantees fault granularity with respect to a given page size (pte,
> pmd, or pud) set at configuration time.
> 
> 2/ Enforces deterministic behavior by being strict about what fault
> scenarios are supported.
> 
> For example, by forcing MADV_DONTFORK semantics and omitting MAP_PRIVATE
> support device-dax guarantees that a mapping always behaves/performs the
> same once established.  It is the "what you see is what you get" access
> mechanism to differentiated memory vs filesystem DAX which has
> filesystem specific implementation semantics.
> 
> Persistent memory is the first target, but the mechanism is also
> targeted for exclusive allocations of performance differentiated memory
> ranges.
> 
> This commit is limited to the base device driver infrastructure to
> associate a dax device with pmem range.
> 
> Cc: Jeff Moyer <jmoyer@...hat.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Reviewed-by: Johannes Thumshirn <jthumshirn@...e.de>

-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
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