From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A83353D648A; Fri, 12 Jun 2026 07:35:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781249729; cv=none; b=F2LnbXQZ4Vc2+rez0n0vqgouVY+YsgH/ftlCefZQKkk/nRVJ6Nf0358mBd8Qjt8HfaTRQ8o37uiXakl7zaJ5i6Xvk7xTvOOT41+62DZQeb+Q0mMIkYrW+XWAX7VnrjaP6yobsc7xmqDFJWFuELj+57RANrb/W8hvvIGuHOgcV6I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781249729; c=relaxed/simple; bh=6PFKtc4OHuGEBph1RwUbyC76NRjLZPimWFCe311V/1Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pEWiPneoHPWQnam/VHgCR+fzFtAxb1QgSnfNuNv0UrrBO+Swqsy4I7stqS/9qj6xt9f37ZN+3mvX5peQVt/kFNjWya4ZZ5jYtIuKH6xFsVHZvshfPK7wR7p6fQugO8dwPTgw2+xWQGskJ5quNUhGtajfsXA/i6aygHd26X0Ql10= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dw41I0KG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dw41I0KG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C1EAE1F000E9; Fri, 12 Jun 2026 07:35:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781249728; bh=S8tXmCVe6Dq2p9EIVnNxhFn9TuFpBDLwCbLsDYh9a/4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=dw41I0KGmcYOKqDkRFzNeMeBtkob/gBxFAWH1wEeldyPh3p+C4YgF7hRiawytWCjm l+tQKR0a9KqVSlZZ044nX9x4gAnA1lr01x+H44DQcoHyRbXVrf6o2p6kB06jmrZJw/ 5sF+D2BW4WvwHvx5174uapQzgoqZK/z2YwdRl/f5IfI5hBJFwVf4/HaiL6QQXX7VTc EZxlVxxaZIRNSjX4EXLzgR2RA/grfrCDN86buvzST9ZRwyZ+FOvehDiv6WTMxEaiqa j4wCgrl70ReuumqCWCywmwW+6jI9TGP3+kL7FcWzXZYMJ5eBB5YHi7tAMIwlSLjMh/ uUr9Aousv83GA== Message-ID: <63ed20dd-e572-4ac5-8cb4-7eed2f42f2fc@kernel.org> Date: Fri, 12 Jun 2026 09:35:22 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests: mm: fix and speedup "droppable" test To: SeongJae Park Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , "Jason A. Donenfeld" , Anthony Yznaga , Mark Brown , Sarthak Sharma , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Aishwarya TCV References: <20260612012910.84424-1-sj@kernel.org> 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: <20260612012910.84424-1-sj@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/12/26 03:29, SeongJae Park wrote: > On Thu, 11 Jun 2026 12:01:55 +0200 "David Hildenbrand (Arm)" wrote: > >> The droppable test currently relies on creating memory pressure in a >> child process to trigger dropping the droppable pages. >> >> That not only takes a long time on some machines (allocating and filling >> all that memory), on large machines this will not work as we hardcode the >> area size to 134217728 bytes. >> >> ... further, we rely on timeouts to detect that memory was not dropped, >> which is really suboptimal. >> >> Instead, let's just use MADV_PAGEOUT on a 2 MiB region. MADV_PAGEOUT works >> with droppable memory even without swap. >> >> There is the low chance of MADV_PAGEOUT failing to drop a page because >> of speculative references. We'll wait 1s and retry 10 times to >> rule that unlikely case out as best as we can. >> >> On a machine without swap: >> >> $ ./droppable >> TAP version 13 >> 1..1 >> ok 1 madvise(MADV_PAGEOUT) behavior >> # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 >> >> Reported-by: Aishwarya TCV >> Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") > > Because this is a fix for a test, I think not Cc-ing stable@ is ok. Further, > arguably this is not a fix but an improvement? No strong opinion, just > thinking loud. The test will hang forever on very large machines and timeout on large machines, so it's a fix not just an improvement. I think Andrew just automatically CCs stable on any test fixes, so yeah, CC; stable makes sense for this one as well. > >> Signed-off-by: David Hildenbrand (Arm) > > Reviewed-by: SeongJae Park > >> --- >> tools/testing/selftests/mm/droppable.c | 46 +++++++++++++++++++--------------- >> 1 file changed, 26 insertions(+), 20 deletions(-) >> >> diff --git a/tools/testing/selftests/mm/droppable.c b/tools/testing/selftests/mm/droppable.c >> index 30c8be37fcb9..57e1b6fc5569 100644 >> --- a/tools/testing/selftests/mm/droppable.c >> +++ b/tools/testing/selftests/mm/droppable.c >> @@ -17,10 +17,10 @@ >> >> int main(int argc, char *argv[]) >> { >> - size_t alloc_size = 134217728; >> - size_t page_size = getpagesize(); >> + const size_t alloc_size = 2 * 1024 * 1024; >> + int retry_count = 10; >> + bool dropped; >> void *alloc; >> - pid_t child; >> >> ksft_print_header(); >> ksft_set_plan(1); >> @@ -35,26 +35,32 @@ int main(int argc, char *argv[]) >> exit(KSFT_FAIL); >> } >> memset(alloc, 'A', alloc_size); >> - for (size_t i = 0; i < alloc_size; i += page_size) >> - assert(*(uint8_t *)(alloc + i)); >> - >> - child = fork(); >> - assert(child >= 0); >> - if (!child) { >> - for (;;) >> - *(char *)malloc(page_size) = 'B'; >> - } >> >> - for (bool done = false; !done;) { >> - for (size_t i = 0; i < alloc_size; i += page_size) { >> - if (!*(uint8_t *)(alloc + i)) { >> - done = true; >> - break; >> + while (retry_count--) { >> + if (madvise(alloc, alloc_size, MADV_PAGEOUT)) { >> + if (errno == EINVAL) { >> + ksft_test_result_skip("madvise(MADV_PAGEOUT) not supported\n"); >> + exit(KSFT_SKIP); > > This check is for a case that this test is running against an old kernel that > doesn't have MADV_PAGEOUT? Yes! > > Assuming so, I was first thinking this check might not really needed, assuming > the test runner would pick the kselftest code from the running kernel's source > code. But I recalled some people do get kselftest code from random place. So > this check seems nice to me. Yeah, we try to handle older kernels on a best-effort basis. This one is rather simple :) Thanks! -- Cheers, David