Re: linux-next: build warnings after merge of the mm tree

Andrew Morton
2024-07-02T03:14:54Z

On Mon, 1 Jul 2024 18:49:12 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:

> Hi all,
>
> After merging the mm tree, today's linux-next build (htmldocs) produced
> these warnings:
>
> Documentation/admin-guide/sysctl/vm.rst:278: ERROR: Unexpected indentation.
> Documentation/admin-guide/sysctl/vm.rst:279: WARNING: Block quote ends without a blank line; unexpected unindent.
>
> Introduced by commit
>
> 2cba7831f62c ("docs: mm: add enable_soft_offline sysctl")

Well that's annoying.

@@ -267,6 +268,37 @@ used::
These are informational only. They do not mean that anything is wrong
with your system. To disable them, echo 4 (bit 2) into drop_caches.

+enable_soft_offline
+===================
+Correctable memory errors are very common on servers. Soft-offline is kernel's
+solution for memory pages having (excessive) corrected memory errors.
+
+For different types of page, soft-offline has different behaviors / costs.
+- For a raw error page, soft-offline migrates the in-use page's content to
+ a new raw page.
+- For a page that is part of a transparent hugepage, soft-offline splits the
+ transparent hugepage into raw pages, then migrates only the raw error page.
+ As a result, user is transparently backed by 1 less hugepage, impacting
+ memory access performance.
+- For a page that is part of a HugeTLB hugepage, soft-offline first migrates
+ the entire HugeTLB hugepage, during which a free hugepage will be consumed
+ as migration target. Then the original hugepage is dissolved into raw
+ pages without compensation, reducing the capacity of the HugeTLB pool by 1.
+
+ ...

This seems a reasonable thing to do so there's probably some way in
which to do it, but a bit of grepping failed to turn up examples in
existing .rst files. Can someone please suggest?