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 A8EE4364E85; Tue, 21 Jul 2026 13:28:21 +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=1784640502; cv=none; b=RKwfWh/+zA+4h0lpyj/dtjKCM5gGpkhhbSKeqAXCU4P83O/Tac4QIRPXjWV1eAnnCUcjujdqc/WoOBrI25J2dgdZxF91nC4EAxQu7CjvlyfI6c8PqYd09nqFe6Rewst41ZvPNSKnk7/sJmvtSk8RYLr+sgIKnm44N0D/h/swy8M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784640502; c=relaxed/simple; bh=1DrzkwYG4DVcLfvK8rN78l2Ib189Ef5Dxe6x+/C7Rsc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=diJFV4Y2fkMHE/QQF33Gy0PoHw7kYW43rtDJneQCFi/vKPIM47pk7bwdFkaBDaL4+7cpgmuQtKuj2CsIABiFnhSKCie4C6Wp0tn5xwNmgntqdMvqVzCFVbzzRC4xCeswG9r2QpBRN8FurOIJjDSCQgM8qJe4WKO/e2bBR8TUzhI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KpJnpT20; 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="KpJnpT20" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80E401F000E9; Tue, 21 Jul 2026 13:28:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784640501; bh=R6fUyFk8ujRTzbRaJmanF803n/mbAv7CSse41ycTcNk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=KpJnpT20QOyKkepzpMkW5nqZGuzmqwLn2yQU67By8k48KdR4iYMJ9bDWPKEIvprRu 4pG9Cq7F6C3mWPzYkptISPkm86QJKYgFYKzgv58AAz1ErdZ/1DMZvRVW4SGLLKf1ST Ba9s+/Fr+nkzmkjWbix78M1cwSc3gDxyLEbNxA7UGNq0gM6MppB5b4F4Qn4CzeBqyu ae499b2FDGEnds5RLdqjNx2YyEQ4KhznYDDJpGlidoqy360ewoHiapGR4X6k5wO7me SSDYddgvEiOIZmBwWeFGSaYjb/5OW6IQkL5y0c0UvgtlHD+NkBUB0MuvDbtZ18PKG0 4wPEzcZglcvnQ== Message-ID: <94ace42d-8d60-4475-953e-74fb3dc23774@kernel.org> Date: Tue, 21 Jul 2026 15:28:13 +0200 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] selftests/mm: transhuge-stress: check duration inside page loop To: Sarthak Sharma , Andrew Morton Cc: Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Mark Brown , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Aishwarya TCV References: <20260720103105.169955-1-sarthak.sharma@arm.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: <20260720103105.169955-1-sarthak.sharma@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/20/26 12:31, Sarthak Sharma wrote: > transhuge-stress.c currently scans memory equal to RAM by default, > in jumps of hugepage size, trying to allocate and split a THP at > each step. After the entire range is covered, it checks whether > elapsed time is greater than the duration. But it is possible > that the THP work it does takes time more than the duration itself, > causing the test to exceed the CI timeout. > > Check the elapsed time after each THP operation. If the duration > has elapsed, break and end the test. Adjust the statistics > calculations to accommodate partially completed passes. Also, > reject sizes which are smaller than a huge page. > > Reported-by: Aishwarya TCV > Suggested-by: Dev Jain > Signed-off-by: Sarthak Sharma > --- > Tested with -d 5 on a machine with about 250 GiB RAM. That is certainly an improvement for running the test, but see below on the overall test: within 5 seconds on that machine, the test is probably completely useless to run. IOW, 5 wasted seconds :) > > Time taken before the patch = 4m26.793s > Time taken after the patch = 0m5.198s > --- > tools/testing/selftests/mm/transhuge-stress.c | 30 ++++++++++++++----- > 1 file changed, 23 insertions(+), 7 deletions(-) > > diff --git a/tools/testing/selftests/mm/transhuge-stress.c b/tools/testing/selftests/mm/transhuge-stress.c > index 8eb0c5630e7e..a0f9fc900360 100644 > --- a/tools/testing/selftests/mm/transhuge-stress.c > +++ b/tools/testing/selftests/mm/transhuge-stress.c > @@ -35,6 +35,7 @@ int main(int argc, char **argv) > size_t map_len; > int pagemap_fd; > int duration = 0; > + double elapsed = 0; > > ksft_print_header(); > > @@ -60,8 +61,6 @@ int main(int argc, char **argv) > len = atoll(argv[i]) << 20; > } > > - ksft_set_plan(1); > - > if (name) { > backing_fd = open(name, O_RDWR); > if (backing_fd == -1) > @@ -78,6 +77,10 @@ int main(int argc, char **argv) > ksft_exit_fail_msg("open pagemap\n"); > > len -= len % HPAGE_SIZE; > + if (len == 0) > + ksft_exit_fail_msg("len must be at least %d MiB\n", > + HPAGE_SIZE >> 20); > + > ptr = mmap(NULL, len + HPAGE_SIZE, PROT_RW, mmap_flags, backing_fd, 0); > if (ptr == MAP_FAILED) > ksft_exit_fail_msg("initial mmap"); > @@ -91,6 +94,7 @@ int main(int argc, char **argv) > if (!map) > ksft_exit_fail_msg("map malloc\n"); > > + ksft_set_plan(1); > clock_gettime(CLOCK_MONOTONIC, &start); > > while (1) { > @@ -125,16 +129,28 @@ int main(int argc, char **argv) > /* split transhuge page, keep last page */ > if (madvise(p, HPAGE_SIZE - psize(), MADV_DONTNEED)) > ksft_exit_fail_msg("MADV_DONTNEED"); > + > + if (duration > 0) { > + clock_gettime(CLOCK_MONOTONIC, &b); > + elapsed = b.tv_sec - start.tv_sec + > + (b.tv_nsec - start.tv_nsec) / 1000000000.; > + if (elapsed >= duration) > + break; > + } > } > clock_gettime(CLOCK_MONOTONIC, &b); > s = b.tv_sec - a.tv_sec + (b.tv_nsec - a.tv_nsec) / 1000000000.; > > ksft_print_msg("%.3f s/loop, %.3f ms/page, %10.3f MiB/s\t" > - "%4d succeed, %4d failed, %4d different pages\n", > - s, s * 1000 / (len >> HPAGE_SHIFT), len / s / (1 << 20), > - nr_succeed, nr_failed, nr_pages); > - > - if (duration > 0 && b.tv_sec - start.tv_sec >= duration) { > + "%4d succeed, %4d failed, %4d different pages\n", > + s, s * 1000 / (nr_failed + nr_succeed), > + s > 0 ? > + (double)(nr_failed + nr_succeed) * > + (HPAGE_SIZE >> 20) / s : > + 0.0, > + nr_succeed, nr_failed, nr_pages); > + > + if (duration > 0 && elapsed >= duration) { > ksft_test_result_pass("Completed\n"); > ksft_finished(); > } Looking into this test here, this is actually the type of test we don't want as a selftests. a) It never fails on actual THP allocation issues, so the test can never fail (only trigger splats etc). b) It relies on magic input parameters nobody ever sets. Setting the value too small (e.g., to 5), will not test anything on a bigger machine, really. Even the default of "20" from run_vmtests.sh is likely insufficient. There an option to set a file when really, nobody does that. We don't want random testing tools to be part of our automated selftests. c) It measures and prints things nobody ever checks I think we should rethink this test as a whole: what could it look like as a proper selftests, whose sole purpose is to be a selftest that passes or fails, reliably. For example, we could a) Allocate as many THPs until it fails b) Split all THPs, keeping only a single page c) Retry allocating THPs and make sure that we succeed in allocating the majority. If not, fail. While making sure that the system is configured properly. To avoid long runtimes, we could consider skipping the tests on larger machines (e.g., > 10s) where allocation would just take too long. That would be more deterministic than what we have here. -- Cheers, David