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[2003:d8:2f20:7500:5f99:9633:990e:138]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-458a99ce1d2sm26772525e9.23.2025.08.01.05.53.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 Aug 2025 05:53:17 -0700 (PDT) Message-ID: <8ba84519-7e69-4058-9ac1-d3e2e622a6ab@redhat.com> Date: Fri, 1 Aug 2025 14:53:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] 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: <20250731122825.2102184-1-usamaarif642@gmail.com> <20250731122825.2102184-5-usamaarif642@gmail.com> <7b13d8b5-a534-47f8-b6c5-09a65bffc691@redhat.com> <22e263a3-a1d2-4159-b3c8-44f7a29bace9@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: e19zmkkpymwcwrpuju4xoytud9p4rk3b X-Rspamd-Queue-Id: 60A4B40007 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1754052802-700363 X-HE-Meta: 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 oq4ltHdK 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >>> + >>> +struct test_results { >>> +    int prctl_get_thp_disable; >> >> The result is always one, does that here make sense? > > Its 3 in the next patch for PR_THP_DISABLE_EXCEPT_ADVISED :) > > I will remove this struct, but I think maybe it might have been a good idea to squash this > with the next patch to show why the struct was useful. I think it's reasonable to keep them separate. > >> >>> +    int prctl_applied_collapse_none; >> >> "prctl_applied" is a bit confusing. And most of these always have the same value. >> >> Can't we special case the remaining two cases on the current policy and avoid this struct compeltely? >> > > The values are different in the next patch when PR_THP_DISABLE_EXCEPT_ADVISED is used. > > Just to explain how I came about using this struct test_results (though it doesnt matter as > I will remove it for the next revision): > I wanted to maximise code reuse and only wanted to have one instance of prctl_thp_disable_test. > I actually started with special casing, but went the brute force way of adding too many if else > statements and it was looking quite messy after I added the tests for PR_THP_DISABLE_EXCEPT_ADVISED. > I saw this struct test_results in another kselftest and thought this should make it much better and > extendable. > > I have removed struct test_results and changed prctl_thp_disable_test to the following for next revision: Yeah, or just duplicate that function and call it prctl_thp_disable_unless_advised_test() in the next patch. Makes the code easier to read and the duplication is limited. -- Cheers, David / dhildenb