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[2003:d8:2f42:b000:db8b:7655:f60f:812b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e760786ceasm1624111f8f.16.2025.09.11.01.46.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Sep 2025 01:46:12 -0700 (PDT) Message-ID: <749511a8-7c57-4f97-9e49-8ebe8befe9aa@redhat.com> Date: Thu, 11 Sep 2025 10:46:10 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory-failure: Disable soft offline for HugeTLB pages by default To: Kyle Meyer , akpm@linux-foundation.org, corbet@lwn.net, linmiaohe@huawei.com, shuah@kernel.org, tony.luck@intel.com Cc: Liam.Howlett@oracle.com, bp@alien8.de, hannes@cmpxchg.org, jack@suse.cz, jane.chu@oracle.com, jiaqiyan@google.com, joel.granados@kernel.org, laoar.shao@gmail.com, lorenzo.stoakes@oracle.com, mclapinski@google.com, mhocko@suse.com, nao.horiguchi@gmail.com, osalvador@suse.de, rafael.j.wysocki@intel.com, rppt@kernel.org, russ.anderson@hpe.com, shawn.fan@intel.com, surenb@google.com, vbabka@suse.cz, linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org References: From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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