Re: [PATCH] mm/memory-failure: Disable soft offline for HugeTLB pages by default

[David Hildenbrand <david@redhat.com>]

On 10.09.25 18:15, Kyle Meyer wrote:
> Soft offlining a HugeTLB page reduces the available HugeTLB page pool.
> Since HugeTLB pages are preallocated, reducing the available HugeTLB
> page pool can cause allocation failures.
> 
> /proc/sys/vm/enable_soft_offline provides a sysctl interface to
> disable/enable soft offline:
> 
> 0 - Soft offline is disabled.
> 1 - Soft offline is enabled.
> 
> The current sysctl interface does not distinguish between HugeTLB pages
> and other page types.
> 
> Disable soft offline for HugeTLB pages by default (1) and extend the
> sysctl interface to preserve existing behavior (2):
> 
> 0 - Soft offline is disabled.
> 1 - Soft offline is enabled (excluding HugeTLB pages).
> 2 - Soft offline is enabled (including HugeTLB pages).
> 
> Update documentation for the sysctl interface, reference the sysctl
> interface in the sysfs ABI documentation, and update HugeTLB soft
> offline selftests.

I'm sure you spotted that the documentation for 
"/sys/devices/system/memory/soft_offline_pag" resides under "testing".

If your read about MADV_SOFT_OFFLINE in the man page it clearly says:

"This feature is intended for testing of memory error-handling code; it 
is available  only if the kernel was configured with CONFIG_MEMORY_FAILURE."

So I'm sorry to say: I miss why we should add all this complexity to 
make a feature used for testing soft-offlining work differently for 
hugetlb folios -- with a testing interface.

-- 
Cheers

David / dhildenb