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([2620:10d:c092:500::7:8979]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45a1b7c18d7sm16194935e9.2.2025.08.14.08.41.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Aug 2025 08:41:20 -0700 (PDT) Message-ID: <0879b2c9-3088-4f92-8d73-666493ec783a@gmail.com> Date: Thu, 14 Aug 2025 16:41:16 +0100 Precedence: bulk X-Mailing-List: linux-kernel@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 , Mark Brown Cc: David Hildenbrand , 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: <13220ee2-d767-4133-9ef8-780fa165bbeb@lucifer.local> <5b341172-5082-4df4-8264-e38a01f7c7d7@lucifer.local> <0b7543dd-4621-432c-9185-874963e8a6af@redhat.com> <5dce29cc-3fad-416f-844d-d40c9a089a5f@lucifer.local> <47e98636-aace-4a42-b6a4-3c63880f394b@sirena.org.uk> <1387eeb8-fc61-4894-b12f-6cae3ad920bd@redhat.com> <620a586e-54a2-4ce0-9cf7-2ddf4b6ef59d@sirena.org.uk> Content-Language: en-US From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 14/08/2025 16:02, Lorenzo Stoakes wrote: > On Thu, Aug 14, 2025 at 02:08:57PM +0100, Mark Brown wrote: >> On Thu, Aug 14, 2025 at 02:59:13PM +0200, David Hildenbrand wrote: >>> On 14.08.25 14:09, Mark Brown wrote: >> >>>> Perhaps this is something that needs considering in the ABI, so >>>> userspace can reasonably figure out if it failed to configure whatever >>>> is being configured due to a missing feature (in which case it should >>>> fall back to not using that feature somehow) or due to it messing >>>> something else up? We might be happy with the tests being version >>>> specific but general userspace should be able to be a bit more robust. >> >>> Yeah, the whole prctl() ship has sailed, unfortunately :( >> >> Perhaps a second call or sysfs file or something that returns the >> supported mask? You'd still have a boostrapping issue with existing >> versions but at least at any newer stuff would be helped. > > Ack yeah I do wish we had better APIs for expressing what was > available/not. Will put this sort of thing on the TODO... > > Overall I don't want to hold this up unnecesarily, and I bow to the > consensus if others feel we ought not to _assume_ same kernel at least best > effort. > > Usama - It's ok to leave it as is in this case since obviously only tip > kernel will have this feature. ah ok, so will keep it at skipping if prctl doesnt work in fixture as is in the current v4 version. I only have the below diff and its equivalent for patch 7 as a difference over this version. Will wait until tomorrow morning incase there are more comments and hopefully send out a last revision! Thanks! diff --git a/tools/testing/selftests/mm/prctl_thp_disable.c b/tools/testing/selftests/mm/prctl_thp_disable.c index 8845e9f414560..e9e519c85224c 100644 --- a/tools/testing/selftests/mm/prctl_thp_disable.c +++ b/tools/testing/selftests/mm/prctl_thp_disable.c @@ -18,6 +18,7 @@ enum thp_collapse_type { THP_COLLAPSE_NONE, + THP_COLLAPSE_MADV_NOHUGEPAGE, THP_COLLAPSE_MADV_HUGEPAGE, /* MADV_HUGEPAGE before access */ THP_COLLAPSE_MADV_COLLAPSE, /* MADV_COLLAPSE after access */ }; @@ -49,6 +50,8 @@ static int test_mmap_thp(enum thp_collapse_type madvise_buf, size_t pmdsize) if (madvise_buf == THP_COLLAPSE_MADV_HUGEPAGE) madvise(mem, pmdsize, MADV_HUGEPAGE); + else if (madvise_buf == THP_COLLAPSE_MADV_NOHUGEPAGE) + madvise(mem, pmdsize, MADV_NOHUGEPAGE); /* Ensure memory is allocated */ memset(mem, 1, pmdsize); @@ -73,6 +76,8 @@ static void prctl_thp_disable_completely_test(struct __test_metadata *const _met /* tests after prctl overrides global policy */ ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_NONE, pmdsize), 0); + ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_NOHUGEPAGE, pmdsize), 0); + ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_HUGEPAGE, pmdsize), 0); ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_COLLAPSE, pmdsize), 0); @@ -84,6 +89,8 @@ static void prctl_thp_disable_completely_test(struct __test_metadata *const _met ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_NONE, pmdsize), thp_policy == THP_ALWAYS ? 1 : 0); + ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_NOHUGEPAGE, pmdsize), 0); + ASSERT_EQ(test_mmap_thp(THP_COLLAPSE_MADV_HUGEPAGE, pmdsize), thp_policy == THP_NEVER ? 0 : 1); > > Cheers, Lorenzo