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[91.12.96.66]) by smtp.gmail.com with ESMTPSA id d6sm21881edm.31.2020.09.10.13.31.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Sep 2020 13:31:10 -0700 (PDT) From: David Hildenbrand Mime-Version: 1.0 (1.0) Subject: Re: Ways to deprecate /sys/devices/system/memory/memoryX/phys_device ? Date: Thu, 10 Sep 2020 22:31:09 +0200 Message-Id: <3E00A442-7107-48DA-8172-EED95F6E1663@redhat.com> References: Cc: David Hildenbrand , Gerald Schaefer , Michal Hocko , "akpm@linux-foundation.org" , Greg KH , =?utf-8?Q?Jan_H=C3=B6ppner?= , Heiko Carstens , "linux-mm@kvack.org" , linux-api@vger.kernel.org, Dave Hansen , "linux-kernel@vger.kernel.org" In-Reply-To: To: Dave Hansen X-Mailer: iPhone Mail (17G68) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0.502 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 3EC3F1804B65A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000012, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > Am 10.09.2020 um 22:01 schrieb Dave Hansen : >=20 > =EF=BB=BFOn 9/10/20 3:20 AM, David Hildenbrand wrote: >> I was just exploring how /sys/devices/system/memory/memoryX/phys_device >> is/was used. It's one of these interfaces that most probably never >> should have been added but now we are stuck with it. >=20 > While I'm all for cleanups, what specific problems is phys_device causing= ? >=20 Mostly stumbling over it, understanding that it is basically unused with ne= w userspace for good reason, questioning its existence. E.g., I am working on virtio-mem support for s390x. Displaying misleading/w= rong phys_device indications isn=E2=80=98t particularly helpful - especiall= y once there are different ways to hotplug memory for an architecture. > Are you hoping that we can just remove users of memoryX/* until there > are no more left, and this is the easiest place to start? At least reducing it to a minimum with clear semantics. Even with automatic= onlining there are still reasons why we need to keep the interface for now= (e.g., reloading kexec to update the kdump headers on memory hot(un)plug).= But also standby memory handling on s399x requires it (->manual onlining).