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From:   David Hildenbrand <david@redhat.com>
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Subject: Re: Ways to deprecate /sys/devices/system/memory/memoryX/phys_device ?
Date:   Fri, 11 Sep 2020 22:49:06 +0200
Message-Id: <00BF194F-9B67-4F7B-AA6F-902E2BCB2F7B@redhat.com>
References: <64ad68af6abe4d6b9a346e777e2bd864@intel.com>
Cc:     David Hildenbrand <david@redhat.com>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        Michal Hocko <mhocko@suse.com>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        =?utf-8?Q?Jan_H=C3=B6ppner?= <hoeppner@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
In-Reply-To: <64ad68af6abe4d6b9a346e777e2bd864@intel.com>
To:     "Luck, Tony" <tony.luck@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> Am 11.09.2020 um 22:09 schrieb Luck, Tony <tony.luck@intel.com>:
>=20
> =EF=BB=BF
>>=20
>> How would it behave after hotplugging a single DIMM  - I assume a single p=
age will only be mapped to that DIMM (otherwise a lot of stuff would habe to=
 be moved around. Would the mapping change after a reboot - especially can a=
 DIMM that could get hotunplugged before suddenly no longer be hotunplugged i=
ndividually?
>=20
>=20
> We don't currently have any platforms that would allow hot adding at the D=
IMM level.
> The Brickland generation of E7 Xeon servers (Ivybridge, Haswell, Broadwell=
) allowed
> for hot plugging a riser card that contained up to 12 DIMMs.
>=20
> If you did add memory it would have to appear at the top of the system phy=
sical
> address space. No interleave (unless you added more than one DIMM in a sin=
gle
> operation).  After a reboot the system would likely shuffle things around t=
o and
> interleave.
>=20

Thanks a lot - so I=E2=80=98m really spoiled by hot(un)plug capabilities in v=
irtualized environments :D

> -Tony