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[2003:d8:2f2b:b200:607d:d3d2:3271:1be0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b79c3ac036sm19299061f8f.15.2025.08.05.07.32.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Aug 2025 07:32:44 -0700 (PDT) Message-ID: Date: Tue, 5 Aug 2025 16:32:43 +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 5/6] selftests: prctl: introduce tests for disabling THPs completely 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> <20250804154317.1648084-6-usamaarif642@gmail.com> <66c2b413-fa60-476a-b88f-542bbda9c89c@redhat.com> <955ed533-dd7e-45e6-a2cb-f379a5878ef7@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 16:26, Usama Arif wrote: > > > On 05/08/2025 13:55, David Hildenbrand wrote: >> On 05.08.25 14:46, Usama Arif wrote: >>> >>> >>> On 05/08/2025 13:39, David Hildenbrand wrote: >>>>> +FIXTURE_SETUP(prctl_thp_disable_completely) >>>>> +{ >>>>> +    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"); >>>>> + >>>>> +    thp_save_settings(); >>>>> +    thp_read_settings(&self->settings); >>>>> +    self->settings.thp_enabled = variant->thp_policy; >>>>> +    self->settings.hugepages[sz2ord(self->pmdsize, getpagesize())].enabled = THP_INHERIT; >>>> >>>> Oh, one more thing: should we set all other sizes also to THP_INHERIT or (for simplicity) THP_NEVER? >>>> >>> >>> hmm do we need to? I am hoping that we should always get the PMD size THP no matter what the policy >>> for others is in the scenario we have? >> >> Assuming 64K is set to "always", couldn't it mislead us in the "madvise"/"never" test cases in some scenarios? >> > > I tried it with 64K to always and seems to be ok. check_huge_anon checks AnonHugepages from smaps which > only indicates the pmd mapped THPs only. So I think should be ok? Ah, yes. If that's the case, then we can focus on PMD only and not care about how the others are configured. -- Cheers, David / dhildenb