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[91.12.97.136]) by smtp.gmail.com with ESMTPSA id u14sm16181358wmc.41.2021.06.07.01.08.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Jun 2021 01:09:00 -0700 (PDT) Subject: Re: [PATCH v1] memory-hotplug.rst: complete admin-guide overhaul To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Oscar Salvador , Mike Kravetz , Mike Rapoport , Dave Hansen , Matthew Wilcox , Anshuman Khandual , Muchun Song , Pavel Tatashin , Jonathan Corbet , Stephen Rothwell , linux-doc@vger.kernel.org References: <20210525102604.8770-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat Message-ID: <14b018b0-aa19-7d00-2861-50d0e5e2bea8@redhat.com> Date: Mon, 7 Jun 2021 10:08:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.06.21 09:51, Michal Hocko wrote: > [Sorry this somehow slipped through cracks] > > On Tue 25-05-21 12:26:04, David Hildenbrand wrote: >> The memory hot(un)plug documentation is outdated and incomplete. Most of >> the content dates back to 2007, so it's time for a major overhaul. >> >> Let's rewrite, reorganize and update most parts of the documentation. In >> addition to memory hot(un)plug, also add some details regarding >> ZONE_MOVABLE, with memory hotunplug being one of its main consumers. >> >> The style of the document is also properly fixed that e.g., "restview" >> renders it cleanly now. >> >> In the future, we might add some more details about virt users like >> virtio-mem, the XEN balloon, the Hyper-V balloon and ppc64 dlpar. > > I haven't really checked the diff but rather looked at the final > outcome. I have to say I like it a lot. Some places are going a bit too > technical for an admin-guide but they are in minority (e.g. locking or > altmap reference). If somebody feels strong then this could get into its > own file but I wouldn't lose sleep over that. I just realized that "Locking Internals" is still a duplicate with core-api/memory-hotplug.rst I thought this (merge issue) was fixed long ago. I'll just remove it from this file, making sure core-api/memory-hotplug.rst is up-to-date > > I would make one thing slightly more explicit though > diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst > index c95f5c2b30dd..5b462aba89cc 100644 > --- a/Documentation/admin-guide/mm/memory-hotplug.rst > +++ b/Documentation/admin-guide/mm/memory-hotplug.rst > @@ -568,6 +568,10 @@ Even with ZONE_MOVABLE, there are some corner cases where offlining a memory > Further, when running into out of memory situations while migrating pages, or > when still encountering permanently unmovable pages within ZONE_MOVABLE > (-> BUG), memory offlining will keep retrying until it eventually succeeds. > +The offlining context can be terminated by a fatal signal. A timeout based > +offlining can be easily implemented by > + > + % timeout $TIMEOUT offline_block | failure_handling > > Locking Internals > ================= > > > In the future I would find some examples of a failure cases we have seen > so far. E.g. offlining failure with dump_page example. Thanks, I'll pick up your change and see if I can get rid of some low-level stuff. I'll address Mike's review shortly and resend. -- Thanks, David / dhildenb