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Subject: Re: [PATCH 0/9] Allow persistent memory to be used like normal RAM
To:     Dave Hansen <dave.hansen@linux.intel.com>,
        linux-kernel@vger.kernel.org
Cc:     dan.j.williams@intel.com, dave.jiang@intel.com, zwisler@kernel.org,
        vishal.l.verma@intel.com, thomas.lendacky@amd.com,
        akpm@linux-foundation.org, mhocko@suse.com,
        linux-nvdimm@lists.01.org, linux-mm@kvack.org,
        ying.huang@intel.com, fengguang.wu@intel.com
References: <20181022201317.8558C1D8@viggo.jf.intel.com>
From:   Brice Goglin <brice.goglin@gmail.com>
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Date:   Mon, 3 Dec 2018 10:22:24 +0100
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Le 22/10/2018 à 22:13, Dave Hansen a écrit :
> Persistent memory is cool.  But, currently, you have to rewrite
> your applications to use it.  Wouldn't it be cool if you could
> just have it show up in your system like normal RAM and get to
> it like a slow blob of memory?  Well... have I got the patch
> series for you!
>
> This series adds a new "driver" to which pmem devices can be
> attached.  Once attached, the memory "owned" by the device is
> hot-added to the kernel and managed like any other memory.  On
> systems with an HMAT (a new ACPI table), each socket (roughly)
> will have a separate NUMA node for its persistent memory so
> this newly-added memory can be selected by its unique NUMA
> node.


Hello Dave

What happens on systems without an HMAT? Does this new memory get merged
into existing NUMA nodes?

Also, do you plan to have a way for applications to find out which NUMA
nodes are "real DRAM" while others are "pmem-backed"? (something like a
new attribute in /sys/devices/system/node/nodeX/) Or should we use HMAT
performance attributes for this?

Brice