Re: [PATCH v2] mm/memory-failure: Support disabling soft offline for HugeTLB pages

Andrew Morton
2025-09-16T03:16:20Z

On Mon, 15 Sep 2025 19:27:41 -0500 Kyle Meyer <kyle.meyer@hpe.com> wrote:

> Soft offlining a HugeTLB page reduces the HugeTLB page pool.
>
> Commit 56374430c5dfc ("mm/memory-failure: userspace controls soft-offlining pages")
> introduced the following sysctl interface to control soft offline:
>
> /proc/sys/vm/enable_soft_offline
>
> The interface does not distinguish between page types:
>
> 0 - Soft offline is disabled
> 1 - Soft offline is enabled
>
> Convert enable_soft_offline to a bitmask and support disabling soft
> offline for HugeTLB pages:
>
> Bits:
>
> 0 - Enable soft offline
> 1 - Disable soft offline for HugeTLB pages
>
> Supported values:
>
> 0 - Soft offline is disabled
> 1 - Soft offline is enabled
> 3 - Soft offline is enabled (disabled for HugeTLB pages)
>
> Existing behavior is preserved.

um, why? What benefit does this patch provide to our users?
Use-cases, before-and-after scenarios, etc?

> Update documentation and HugeTLB soft offline self tests.
>
> Reported-by: Shawn Fan <shawn.fan@intel.com>

Interesting. What did Shawn report? (Closes:!).

> Suggested-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
>
> ...
>
> .../ABI/testing/sysfs-memory-page-offline | 3 ++
> Documentation/admin-guide/sysctl/vm.rst | 28 ++++++++++++++++---
> mm/memory-failure.c | 17 +++++++++--
> .../selftests/mm/hugetlb-soft-offline.c | 19 ++++++++++---
> 4 files changed, 56 insertions(+), 11 deletions(-)

I'll add it because testing, but please do explain why I added it?