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imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=QWGtMWLa; spf=pass (imf28.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778674231; a=rsa-sha256; cv=none; b=j5tv0Iy7p+1o6LhXwvCzBx6rUdmMfzX8jg40cbbuQvp+QUOkBRQMCXLixB5OkSpQcA0AnZ d+zqaNCeAFiqG5IGcNEZy1bqSnyx4PRYpPUMaqVKKCOlGP/Dym8AEi4qx6+rAt8mWb3WZ2 8TmLQAJ5G3wVKxxi07yXkw1DDkTVWh4= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 0B60260121; Wed, 13 May 2026 12:10:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80B42C2BCB7; Wed, 13 May 2026 12:10:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778674230; bh=DKsaSfcfuE1IVUrZuwxuOKUdV2c4V7dwWzUcqfRcakg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=QWGtMWLaBDi9QplgclFyV9E7EYmvm2m2mtJk+Q2QlJgCMFc6T0CBreB+g1kFIN1jB h9Dvmb9bAuE1t+CGkTs/AXddm5G+oG/BRz4oGwD3wOUr+KMcUZ4zgjMpktA1HzrJ/O 9FCU/X/OfkyKdTufMokoPzxPigrEnx1K8AYKltZnRt7lKf6olDPGZU1f0FnJ/TR33C saSQEbmmDHNtaJhqIC+f++57hEezrT4l5zhorNpJF3p5ppddWXnyaKekhfFOzt7VS2 ceJLkQxmxwxG8xuEeBK4/7u0mv7bLVhlPv75hAGRJDnmS1nJMPW94tCkteIWdmEx7z i02HiNcB+sucQ== Message-ID: <962c2a3d-0502-44b9-a115-863b513bafe2@kernel.org> Date: Wed, 13 May 2026 14:10:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/5] ksm: add mremap selftests for ksm_rmap_walk To: xu.xin16@zte.com.cn, ljs@kernel.org, akpm@linux-foundation.org Cc: hughd@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, michel@lespinasse.org References: <20260503205153715oK1yza2bba5lfAl3QwiPx@zte.com.cn> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260503205153715oK1yza2bba5lfAl3QwiPx@zte.com.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: A089CC0002 X-Rspamd-Server: rspam06 X-Stat-Signature: omcoktkdhf1rp4npob51ypy8t46idf19 X-HE-Tag: 1778674231-798190 X-HE-Meta: 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 REFcV7Ea ivQRuyfO18jT3p0aHj1bQA/JR1W5HjtA/eByl6YxMm6KGOEqKtFgqTo6vEAMHtvdl2eMmFPFs76/wbD9qK1dcqPz/uumlmCoGWoin7YuW2Y4S1TrpgFwwxnrTZpoAiS6aXUppFZZ3T032joBcSL4Mun2oYnqfAhthgySF9lSlpF22NX2mdmpOWJnZ7FXZQpTHWoh2zuh5paTwDISInGVg4MGTgGsy5QNC6RvSTRp9XbTpje6oAI8dGGv/NSMpliWg64nBT7dtVdp6lPzG7qttOUCHRFRn8Vs5W/NFvWSCS/PQaDWKbL8hEDbd5YJeaY2GOD5cXT14l949lJ9HMiBnpdTgutuzZJp2sRPzMfzaaMIceVAPHRv6r9YOs8u2ydOTHZwITsbpWCN12pG5AfETTK63qwVUPl5KiP6A Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/3/26 14:51, xu.xin16@zte.com.cn wrote: > From: xu xin > The existing tools/testing/selftests/mm/rmap.c has already one testcase > for ksm_rmap_walk in TEST_F(migrate, ksm), which takes use of migration > of page from one NUMA node to another NUMA node. However, it just lacks > the scenario of mremapped VMAs. > > There are one worker process and several checker processes, and in worker, > we add the calling of mremap() and then trigger KSM to merge pages before > migrating, , which is specailly to test a optimization which is introduced > by this patch ("ksm: Optimize rmap_walk_ksm by passing a suitable address > range"). In other checker processes, we just trigger KSM to merge pages > from each child process and check their PFN. > > This test can reproduce the issue that Hugh points out at > https://lore.kernel.org/all/02e1b8df-d568-8cbb-b8f6-46d5476d9d75@google.com/ > > Signed-off-by: xu xin > --- > tools/testing/selftests/mm/rmap.c | 79 ++++++++++++++++++++++++++++ > tools/testing/selftests/mm/vm_util.c | 38 +++++++++++++ > tools/testing/selftests/mm/vm_util.h | 2 + > 3 files changed, 119 insertions(+) > > diff --git a/tools/testing/selftests/mm/rmap.c b/tools/testing/selftests/mm/rmap.c > index 53f2058b0ef2..fced1f6304ac 100644 > --- a/tools/testing/selftests/mm/rmap.c > +++ b/tools/testing/selftests/mm/rmap.c > @@ -430,4 +430,83 @@ TEST_F(migrate, ksm) > propagate_children(_metadata, data); > } > > +static void prepare_two_pages(struct global_data *data) > +{ > + /* Allocate exactly 2 pages for the test */ > + data->mapsize = 2 * getpagesize(); > + data->region = mmap(NULL, data->mapsize, PROT_READ | PROT_WRITE, > + MAP_PRIVATE | MAP_ANON, -1, 0); > + if (data->region == MAP_FAILED) > + ksft_exit_fail_perror("mmap failed"); > + > + /* Fill both pages with identical content to encourage KSM merging */ > + memset(data->region, 0x77, data->mapsize); > +} > + > +static int mremap_merge_and_migrate(struct global_data *data) > +{ > + int ret, pagemap_fd; > + void *old_region = data->region; > + unsigned long page_sz = getpagesize(); > + > + /* > + * Mremap the second page to the first page's location (FIXED). > + * This effectively overwrites the first page, leaving the second page > + * unmapped. The physical page originally at the second page is now > + * mapped at the first page's virtual address. > + */ But if there is only a single page, why should it get merged by KSM? -- Cheers, David