From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793872990; b=SwbTPwv1lO7ww0Pa3lFansi3ThIBjwgwpQGtdY6SDfmCIOEDVmTh5X3et4Fv1ARL3mIN YMnt80XBbE4vWttprLsfJLYmG1IDMsbt+/BZpR5LwxzRm1Zr6Gkdnnjt35pUi4HVciYKx LcF85m0zuxsV1MhHsfWkfYqJ7E4vcn3FhRUa7pX2M6YiotewmKEz5PlzJ0tJgPDvMzW3r AemVv6R87LUeb2+Wqz4Mn+PmOOW0TdbZjedpO8YCgpJG1p4YXaGIe/vHN8JmiWa9wCg24 5v8IUGktPb5jFu/RXjmkFk/oxC4fozCkFU7s3bn05DIZ4plaIPDNEWV4LtGWfkMI5xw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793872990; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=YGxMLGOpmO21KJ2mjD9khBg9SC63tjkRy41YsLQwOKA=; b=mzI8+UFvPD7ATnEnk/SbrJOkjzc7HXb7DfD/WGEaz4tfNiMtttRzw/3kK2vGrL+9SEdY O4YQrVCgdm0fzuE9dEtIPjSRyOCJM47COFT+k3DcYz0PjyMIddEe4k/p8Yy43QIwBolBj BkCbUoGezJmmeYZ9oomQZ+s7qi7UcnsIXurdvfLnvX8ENsK58M/Q2bxBMM4cryP3V3Fh6 vyvA8Uz7gDTbAXUkPPW0xqK4bNj42rIW6aW33BOnYxJ4i/jgQ2RvJALkVWgVWzch/Wjsz JdVDYD7ykhgrpclP6kreLLmyujyoYEcrYk0w6sIxeN4rxiELS6Z9ORlTwQlSbuFW3nw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=X23c9kWV; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5138F606A31B; Thu, 5 Nov 2026 10:03:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=X23c9kWV Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E8C11F000C1; Thu, 5 Nov 2026 10:03:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793872989; bh=YGxMLGOpmO21KJ2mjD9khBg9SC63tjkRy41YsLQwOKA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=X23c9kWVkPgMqf9QyBhUBCMJnR9wXAEOhBgM4zA+aaLN25UZaS72McMQVN0/qvLUj gyk5MOm29CmrgYJH9yay9R0doiqzvqabiwazIkyDlhKcCIJ8plw01qp3O1I61UTMb2 4sDnNnTwzudp4tadLZyxoi3npf+TTtP02nBBVgnX6ZEX+80DAIf/GFQwwsOf2R8b+Z hlvrM8pjyLZtfwgzHKBPb+KT/mu5ORHSRwxL/NWD+/twyME/sINzijVNN8QeVMy0SY SkJJrq4ukXNq1AAh4nbKw54nZ/nmzNeR2PTlSjc9shb0e57kDG9CxL0ftVLrYYgdTM MLp33ObuR7rRg== Message-ID: Date: Thu, 5 Nov 2026 11:03:03 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] selftests/mm: cover merging KSM pages aged by smart scan To: Qiliang Yuan , Andrew Morton , Xu Xin , Chengming Zhou , Stefan Roesch , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20261105-bug-mm-ksm-smart-scan-align-skips-v2-0-8a9780b6844e@gmail.com> <20261105-bug-mm-ksm-smart-scan-align-skips-v2-2-8a9780b6844e@gmail.com> 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: <20261105-bug-mm-ksm-smart-scan-align-skips-v2-2-8a9780b6844e@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/5/26 10:36, Qiliang Yuan wrote: > ksm_functional_tests checks merging and unmerging with ksmd's default > settings, but nothing there exercises smart scan, which skips pages KSM > has failed to merge for a while. > > Smart scan used to time those skips per page, so two identical pages > that became mergeable some scans apart could end up never being looked > at in the same scan, and were never merged. "mm/ksm: align smart scan > skips with the scan number" fixed that. > > Add a case that lets sixteen unique pages age for a dozen scans, then > makes a duplicate of each mergeable one scan apart, and expects every > pair to be merged 32 scans later: > > kernel failures, two boots > before the fix 20/20, 20/20 > with the fix 0/20, 0/20 > > Signed-off-by: Qiliang Yuan > --- > tools/testing/selftests/mm/ksm_functional_tests.c | 108 +++++++++++++++++++++- > 1 file changed, 107 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c > index 31c06c72203fd..71d9b3cbdb8c1 100644 > --- a/tools/testing/selftests/mm/ksm_functional_tests.c > +++ b/tools/testing/selftests/mm/ksm_functional_tests.c > @@ -695,6 +695,111 @@ static void test_fork_ksm_merging_page_count(void) > munmap(map, size); > } > > +static int ksm_wait_full_scans(long nr) > +{ > + long start, cur; > + > + start = ksm_get_full_scans(); > + if (start < 0) > + return start; > + do { > + cur = ksm_get_full_scans(); > + if (cur < 0) > + return cur; > + } while (cur < start + nr); > + > + return 0; > +} > + This looks a lot like the logic we have in ksm_start(). Likely that logic there should be factored out into a common helper. > +static void test_merge_aged_pairs(void) > +{ > + const unsigned int pairs = 16; > + const unsigned long size = 2 * pairs * pagesize; > + char *map, old_smart_scan = '1'; > + int smart_scan_fd; > + unsigned int i; > + > + ksft_print_msg("[RUN] %s\n", __func__); > + > + smart_scan_fd = open("/sys/kernel/mm/ksm/smart_scan", O_RDWR); > + if (smart_scan_fd < 0) { > + ksft_test_result_skip("smart_scan not supported\n"); > + return; > + } > + if (pread(smart_scan_fd, &old_smart_scan, 1, 0) != 1 || > + pwrite(smart_scan_fd, "1", 1, 0) != 1) { > + ksft_test_result_fail("Enabling smart_scan failed\n"); > + goto close_fd; > + } Can we have a helper to enable/disable smart scan? Likely belongs into utils as well. -- Cheers, David