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[2003:d8:2f44:3e00:9fca:7d89:a265:56f3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ba54b6c93fsm688042f8f.12.2025.08.14.02.32.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Aug 2025 02:32:57 -0700 (PDT) Message-ID: <0b7543dd-4621-432c-9185-874963e8a6af@redhat.com> Date: Thu, 14 Aug 2025 11:32:55 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 7/7] selftests: prctl: introduce tests for disabling THPs except for madvise To: Lorenzo Stoakes Cc: Usama Arif , Andrew Morton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, corbet@lwn.net, rppt@kernel.org, surenb@google.com, mhocko@suse.com, hannes@cmpxchg.org, baohua@kernel.org, shakeel.butt@linux.dev, riel@surriel.com, ziy@nvidia.com, laoar.shao@gmail.com, dev.jain@arm.com, baolin.wang@linux.alibaba.com, npache@redhat.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, vbabka@suse.cz, jannh@google.com, Arnd Bergmann , sj@kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@meta.com References: <20250813135642.1986480-1-usamaarif642@gmail.com> <20250813135642.1986480-8-usamaarif642@gmail.com> <13220ee2-d767-4133-9ef8-780fa165bbeb@lucifer.local> <5b341172-5082-4df4-8264-e38a01f7c7d7@lucifer.local> 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 13.08.25 20:52, Lorenzo Stoakes wrote: > On Wed, Aug 13, 2025 at 06:24:11PM +0200, David Hildenbrand wrote: >>>> + >>>> +FIXTURE_SETUP(prctl_thp_disable_except_madvise) >>>> +{ >>>> + if (!thp_available()) >>>> + SKIP(return, "Transparent Hugepages not available\n"); >>>> + >>>> + self->pmdsize = read_pmd_pagesize(); >>>> + if (!self->pmdsize) >>>> + SKIP(return, "Unable to read PMD size\n"); >>>> + >>>> + if (prctl(PR_SET_THP_DISABLE, 1, PR_THP_DISABLE_EXCEPT_ADVISED, NULL, NULL)) >>>> + SKIP(return, "Unable to set PR_THP_DISABLE_EXCEPT_ADVISED\n"); >>> >>> This should be a test fail I think, as the only ways this could fail are >>> invalid flags, or failure to obtain an mmap write lock. >> >> Running a kernel that does not support it? > > I can't see anything in the kernel to #ifdef it out so I suppose you mean > running these tests on an older kernel? Yes. > > But this is an unsupported way of running self-tests, they are tied to the > kernel version in which they reside, and test that specific version. > > Unless I'm missing something here? I remember we allow for a bit of flexibility when it is simple to handle. Is that documented somewhere? > >> >> We could check the errno to distinguish I guess. > > Which one? manpage says -EINVAL, but can also be due to incorrect invocation, > which would mean a typo could mean tests pass but your tests do nothing :) Right, no ENOSYS in that case to distinguish :( -- Cheers David / dhildenb