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[213.151.95.130]) by smtp.gmail.com with ESMTPSA id m10sm20048223wrx.19.2020.01.27.01.23.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jan 2020 01:23:36 -0800 (PST) Date: Mon, 27 Jan 2020 10:23:34 +0100 From: Michal Hocko To: "Fontenot, Nathan" Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dan Williams , Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , powerpc-utils-devel@googlegroups.com, util-linux@vger.kernel.org, Badari Pulavarty , Robert Jennings , Heiko Carstens , Karel Zak Subject: Re: [PATCH RFC] drivers/base/memory.c: indicate all memory blocks as removable Message-ID: <20200127092334.GB1183@dhcp22.suse.cz> References: <20200124155336.17126-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Fri 24-01-20 13:10:22, Fontenot, Nathan wrote: > It's been awhile since I've looked at the powerpc-utils drmgr command and > pseries DLPAR code but a quick scan makes and it appears that it hasn't changed > too much. Given that, some thoughts. > > The sysfs 'removable' file was a great help when memory DLPAR was driven > from userspace in the powerpc-utils drmgr command. Having this check did improve > performance though I can't point to any numbers. Do you still have an access to the HW to give it a try? > Currently, memory DLPAR is done completely in the kernel. The request is > initiated from drmgr writing to /sys/kernel/dlpar (for pHyp partitions) > or from a hotplug interrupt (for guests). I don't believe the 'removable' > sysfs file is used in either of these paths by drmgr. The only time it is > used is on older kernels that do not support in-kernel memory DLPAR. > > Given this, I don't think removing the 'removable' sysfs file would cause any > issues for the drmgr command. The only scenario I can think of is using an old > version of drmgr that does not support in-kernel memory DLPAR on a new kernel > where the 'removable' sysfs file has been removed. This doesn't seem likely > though and drmgr could be updated to detect this. Thanks for the information! -- Michal Hocko SUSE Labs