linux-kernel - RE: Ways to deprecate /sys/devices/system/memory/memoryX/phys

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Date:   Fri, 11 Sep 2020 19:35:24 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Hansen, Dave" <dave.hansen@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>
CC:     Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jan Höppner <hoeppner@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: Ways to deprecate /sys/devices/system/memory/memoryX/phys_device
 ?

> It's actually really hard to map a DIMM to a physical address.
> Interleaving can mean that one page actually spans a bunch of DIMMs.

Heh! If NUMA mode is turned off your single page may have cache lines
from *every* DIMM in the system. Even with NUMA turned on the page
will have cache lines from every DIMM on the socket.

-Tony