linux-kernel - Re: [PATCH v2] mm: Only re-generate demotion targets when a numa node changes its N

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Message-ID: <6b63d2ad-9b21-3fd6-37b4-31d7ad804c30@intel.com>
Date:   Mon, 14 Mar 2022 08:20:57 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Oscar Salvador <osalvador@...e.de>,
        "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Abhishek Goel <huntbag@...ux.vnet.ibm.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: Only re-generate demotion targets when a numa node
 changes its N_CPU state

On 3/14/22 08:13, Oscar Salvador wrote:
> On Mon, Mar 14, 2022 at 09:03:59AM +0800, Huang, Ying wrote:
>> Oscar Salvador <osalvador@...e.de> writes:
>> On host machine, PMEM is always exposed via memory hotplug.  But later
>> on, we found that for guest system it's possible for PMEM to be exposed
>> as normal memory.
> Could you please elaborate on that? How is it done? I would love to hear the
> details.

Qemu, for instance, has a "mem-path" argument.  It's typically used for
using hugetlbfs as guest memory.  But, there's nothing stopping you from
pointing it to a DAX device or a file on a DAX filesystem that's backed
by pmem.