Re: [PATCH v1] memory-hotplug.rst: complete admin-guide overhaul

[Michal Hocko <mhocko@suse.com>]

[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 The memory hot(un)plug documentation is outdated and incomplete.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 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.

> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Muchun Song <songmuchun@bytedance.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: linux-doc@vger.kernel.org
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks a lot David!
-- 
Michal Hocko
SUSE Labs