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[195.135.220.15]) by mx.google.com with ESMTPS id f22si22429032eda.203.2019.07.31.07.14.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jul 2019 07:14:12 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B7F4DAB9B; Wed, 31 Jul 2019 14:14:11 +0000 (UTC) Date: Wed, 31 Jul 2019 16:14:11 +0200 From: Michal Hocko To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , Pavel Tatashin , Dan Williams , Oscar Salvador Subject: Re: [PATCH v1] drivers/base/memory.c: Don't store end_section_nr in memory blocks Message-ID: <20190731141411.GU9330@dhcp22.suse.cz> References: <20190731122213.13392-1-david@redhat.com> <20190731124356.GL9330@dhcp22.suse.cz> <20190731132534.GQ9330@dhcp22.suse.cz> <58bd9479-051b-a13b-b6d0-c93aac2ed1b3@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <58bd9479-051b-a13b-b6d0-c93aac2ed1b3@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 31-07-19 15:42:53, David Hildenbrand wrote: > On 31.07.19 15:25, Michal Hocko wrote: [...] > > I know we have documented this as an ABI and it is really _sad_ that > > this ABI didn't get through normal scrutiny any user visible interface > > should go through but these are sins of the past... > > A quick google search indicates that > > Kata containers queries the block size: > https://github.com/kata-containers/runtime/issues/796 > > Powerpc userspace queries it: > https://groups.google.com/forum/#!msg/powerpc-utils-devel/dKjZCqpTxus/AwkstV2ABwAJ > > I can imagine that ppc dynamic memory onlines only pieces of added > memory - DIMMs AFAIK (haven't looked at the details). > > There might be more users. Thanks! I suspect most of them are just using the information because they do not have anything better. Thinking about it some more, I believe that we can reasonably provide both APIs controlable by a command line parameter for backwards compatibility. It is the hotplug code to control sysfs APIs. E.g. create one sysfs entry per add_memory_resource for the new semantic. It is some time since I've checked the ACPI side of the matter but that code shouldn't really depend on a particular size of the memblock either when trigerring udev events. I might be wrong here of course. -- Michal Hocko SUSE Labs