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[2003:d8:2f2b:b200:607d:d3d2:3271:1be0]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-459db13fc9fsm75518385e9.7.2025.08.05.05.29.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Aug 2025 05:29:19 -0700 (PDT) Message-ID: Date: Tue, 5 Aug 2025 14:29:17 +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 v3 6/6] selftests: prctl: introduce tests for disabling THPs except for madvise To: Usama Arif , Andrew Morton , linux-mm@kvack.org Cc: 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, lorenzo.stoakes@oracle.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: <20250804154317.1648084-1-usamaarif642@gmail.com> <20250804154317.1648084-7-usamaarif642@gmail.com> <9bcb1dee-314e-4366-9bad-88a47d516c79@redhat.com> <5dc09930-e137-47ba-a98f-416d3319c8be@gmail.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 05.08.25 14:19, Usama Arif wrote: > > > On 05/08/2025 11:36, David Hildenbrand wrote: >> On 04.08.25 17:40, Usama Arif wrote: >>> The test will set the global system THP setting to never, madvise >>> or always depending on the fixture variant and the 2M setting to >>> inherit before it starts (and reset to original at teardown) >>> >>> This tests if the process can: >>> - successfully set and get the policy to disable THPs expect for madvise. >>> - get hugepages only on MADV_HUGE and MADV_COLLAPSE if the global policy >>>    is madvise/always and only with MADV_COLLAPSE if the global policy is >>>    never. >>> - successfully reset the policy of the process. >>> - after reset, only get hugepages with: >>>    - MADV_COLLAPSE when policy is set to never. >>>    - MADV_HUGE and MADV_COLLAPSE when policy is set to madvise. >>>    - always when policy is set to "always". >>> - repeat the above tests in a forked process to make sure  the policy is >>>    carried across forks. >>> >>> Signed-off-by: Usama Arif >>> --- >> >> [...] >> >>> +FIXTURE_VARIANT(prctl_thp_disable_except_madvise) >>> +{ >>> +    enum thp_enabled thp_policy; >>> +}; >>> + >>> +FIXTURE_VARIANT_ADD(prctl_thp_disable_except_madvise, never) >>> +{ >>> +    .thp_policy = THP_NEVER, >>> +}; >>> + >>> +FIXTURE_VARIANT_ADD(prctl_thp_disable_except_madvise, madvise) >>> +{ >>> +    .thp_policy = THP_MADVISE, >>> +}; >>> + >>> +FIXTURE_VARIANT_ADD(prctl_thp_disable_except_madvise, always) >>> +{ >>> +    .thp_policy = THP_ALWAYS, >>> +}; >>> + >>> +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"); >> >> Should we test here if the kernel knows PR_THP_DISABLE_EXCEPT_ADVISED, and if not, skip? >> >> Might be as simple as trying issuing two prctl, and making sure the first disabling attempt doesn't fail. If so, SKIP. >> >> Nothing else jumped at me. Can you include a test run result in the patch description? >> > > Instead of 2 prctls, I think doing just the below should be enough: > > diff --git a/tools/testing/selftests/mm/prctl_thp_disable.c b/tools/testing/selftests/mm/prctl_thp_disable.c > index 93cedaa59854..da28bc4441ed 100644 > --- a/tools/testing/selftests/mm/prctl_thp_disable.c > +++ b/tools/testing/selftests/mm/prctl_thp_disable.c > @@ -236,6 +236,9 @@ FIXTURE_SETUP(prctl_thp_disable_except_madvise) > 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"); > + > thp_save_settings(); > thp_read_settings(&self->settings); > self->settings.thp_enabled = variant->thp_policy; Then probably best to remove the ASSERT_EQ(prctl(PR_SET_THP_DISABLE, 1, PR_THP_DISABLE_EXCEPT_ADVISED, NULL, NULL), 0); From both test functions? You can consider doing the same in patch #5. -- Cheers, David / dhildenb