linux-kernel - Re: [PATCH 0/9] Allow persistent memory to be used like normal RAM

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Message-ID: <ffeb6225-6d5c-099e-3158-4711c879ec23@gmail.com>
Date:   Mon, 3 Dec 2018 10:22:24 +0100
From:   Brice Goglin <brice.goglin@...il.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Cc:     dan.j.williams@...el.com, dave.jiang@...el.com, zwisler@...nel.org,
        vishal.l.verma@...el.com, thomas.lendacky@....com,
        akpm@...ux-foundation.org, mhocko@...e.com,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
        ying.huang@...el.com, fengguang.wu@...el.com
Subject: Re: [PATCH 0/9] Allow persistent memory to be used like normal RAM

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