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Thu, 2 Apr 2026 06:32:47 GMT Received: from smtprelay02.wdc07v.mail.ibm.com ([172.16.1.69]) by ppma12.dal12v.mail.ibm.com (PPS) with ESMTPS id 4d6sass3vp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 02 Apr 2026 06:32:47 +0000 Received: from smtpav05.wdc07v.mail.ibm.com (smtpav05.wdc07v.mail.ibm.com [10.39.53.232]) by smtprelay02.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 6326Wksb23200410 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 2 Apr 2026 06:32:47 GMT Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D1A8058053; Thu, 2 Apr 2026 06:32:46 +0000 (GMT) Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ACB6D5805D; Thu, 2 Apr 2026 06:32:41 +0000 (GMT) Received: from [9.124.211.187] (unknown [9.124.211.187]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 2 Apr 2026 06:32:41 +0000 (GMT) Message-ID: <687b02d6-7bf7-4d40-b6d5-7ed627ed5f34@linux.ibm.com> Date: Thu, 2 Apr 2026 12:02:40 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] selftests/mm: hmm-tests: don't hardcode THP size to 2MB To: Alistair Popple , linux-mm@kvack.org Cc: zenghui.yu@linux.dev, Liam.Howlett@oracle.com, akpm@linux-foundation.org, david@kernel.org, jgg@ziepe.ca, leon@kernel.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, dri-devel@lists.freedesktop.org, balbirs@nvidia.com References: <20260331063445.3551404-1-apopple@nvidia.com> <20260331063445.3551404-3-apopple@nvidia.com> Content-Language: en-IN From: Sayali Patil In-Reply-To: <20260331063445.3551404-3-apopple@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: 4X0aRbdByxN6rVrirDnZ3yUrCSbbLMeP X-Authority-Analysis: v=2.4 cv=KslAGGWN c=1 sm=1 tr=0 ts=69ce0d91 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=Ikd4Dj_1AAAA:8 a=LQv_0jpOlx7rUgCL860A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDAyMDA1NCBTYWx0ZWRfX4V5E8imXBwy4 GYN3lXKp56QjI9xZpGaaAtbkJv3OACX34+sw3glCV2lYhu39nJqzZG587QQbre0XDXFPMGgbwA5 6dnLanmDvsj7lfSfm2WsHlQYUKplJzSDK779fAZWTNZKp0ELMprRjjiK+Wy2UK7DRZNK+HrWcZw tXkJy1tzWlhpvWAt/hs2lOaE3w3s9MbecVNX8CBzFAyk7mrqMnQ25EFhs3KfezsyOj1/gi5zbua axVAIcmwfkiTawwgKxBvlqf5Z9gbLzDZj9Ce/EaosVXTNLicKWhimeA/ur6jaltIFNNhk7RDydm vuOmz2p7KjJNP4gv8IGuw9JyA4zQpG4oj1zVop31L+QYxTZDH5hT0VbI30v85XUwgH6ty4Lvn49 Y8nG6bnh+ha8ibkn6oM+KP9dqwd1Ssf83WjVdRyHTQOUyFCDlp3KcDvEZZioT5herF3eY2BHotu 05yEL8aKlQFZQw30bNw== X-Proofpoint-ORIG-GUID: Gb506S43fRUA46xUofpLS-Zj9GZH9vgD X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-02_01,2026-04-01_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 impostorscore=0 clxscore=1011 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2604020054 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 31/03/26 12:04, Alistair Popple wrote: > Several HMM tests hardcode TWOMEG as the THP size. This is wrong on > architectures where the PMD size is not 2MB such as arm64 with 64K base > pages where THP is 512MB. Fix this by using read_pmd_pagesize() from > vm_util instead. > > While here also replace the custom file_read_ulong() helper used to > parse the default hugetlbfs page size from /proc/meminfo with the > existing default_huge_page_size() from vm_util. > > [1] https://lore.kernel.org/linux-mm/8bd0396a-8997-4d2e-a13f-5aac033083d7@linux.dev/ > > Fixes: fee9f6d1b8df ("mm/hmm/test: add selftests for HMM") > Fixes: 519071529d2a ("selftests/mm/hmm-tests: new tests for zone device THP migration") > Reported-by: Zenghui Yu > Closes: https://lore.kernel.org/linux-mm/8bd0396a-8997-4d2e-a13f-5aac033083d7@linux.dev/ > Signed-off-by: Alistair Popple > --- > tools/testing/selftests/mm/hmm-tests.c | 83 +++++--------------------- > 1 file changed, 16 insertions(+), 67 deletions(-) > > diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c > index e8328c89d855..788689497e92 100644 > --- a/tools/testing/selftests/mm/hmm-tests.c > +++ b/tools/testing/selftests/mm/hmm-tests.c > @@ -34,6 +34,7 @@ > */ > #include > #include > +#include > > struct hmm_buffer { > void *ptr; > @@ -548,7 +549,7 @@ TEST_F(hmm, anon_write_child) > > for (migrate = 0; migrate < 2; ++migrate) { > for (use_thp = 0; use_thp < 2; ++use_thp) { > - npages = ALIGN(use_thp ? TWOMEG : HMM_BUFFER_SIZE, > + npages = ALIGN(use_thp ? read_pmd_pagesize() : HMM_BUFFER_SIZE, > self->page_size) >> self->page_shift; > ASSERT_NE(npages, 0); > size = npages << self->page_shift; Can we handle the case where read_pmd_pagesize() returns 0? Currently, it’s passed to ALIGN(), which could produce unexpected results if 0 is returned. Perhaps we can add a fallback to 2MB in that case. > @@ -728,7 +729,7 @@ TEST_F(hmm, anon_write_huge) > int *ptr; > int ret; > > - size = 2 * TWOMEG; > + size = 2 * read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); > @@ -744,7 +745,7 @@ TEST_F(hmm, anon_write_huge) > buffer->fd, 0); > ASSERT_NE(buffer->ptr, MAP_FAILED); > > - size = TWOMEG; > + size /= 2; > npages = size >> self->page_shift; > map = (void *)ALIGN((uintptr_t)buffer->ptr, size); > ret = madvise(map, size, MADV_HUGEPAGE); > @@ -770,54 +771,6 @@ TEST_F(hmm, anon_write_huge) > hmm_buffer_free(buffer); > } > > -/* > - * Read numeric data from raw and tagged kernel status files. Used to read > - * /proc and /sys data (without a tag) and from /proc/meminfo (with a tag). > - */ > -static long file_read_ulong(char *file, const char *tag) > -{ > - int fd; > - char buf[2048]; > - int len; > - char *p, *q; > - long val; > - > - fd = open(file, O_RDONLY); > - if (fd < 0) { > - /* Error opening the file */ > - return -1; > - } > - > - len = read(fd, buf, sizeof(buf)); > - close(fd); > - if (len < 0) { > - /* Error in reading the file */ > - return -1; > - } > - if (len == sizeof(buf)) { > - /* Error file is too large */ > - return -1; > - } > - buf[len] = '\0'; > - > - /* Search for a tag if provided */ > - if (tag) { > - p = strstr(buf, tag); > - if (!p) > - return -1; /* looks like the line we want isn't there */ > - p += strlen(tag); > - } else > - p = buf; > - > - val = strtol(p, &q, 0); > - if (*q != ' ') { > - /* Error parsing the file */ > - return -1; > - } > - > - return val; > -} > - > /* > * Write huge TLBFS page. > */ > @@ -826,15 +779,13 @@ TEST_F(hmm, anon_write_hugetlbfs) > struct hmm_buffer *buffer; > unsigned long npages; > unsigned long size; > - unsigned long default_hsize; > + unsigned long default_hsize = default_huge_page_size(); > unsigned long i; > int *ptr; > int ret; > > - default_hsize = file_read_ulong("/proc/meminfo", "Hugepagesize:"); > - if (default_hsize < 0 || default_hsize*1024 < default_hsize) > + if (!default_hsize) > SKIP(return, "Huge page size could not be determined"); > - default_hsize = default_hsize*1024; /* KB to B */ > > size = ALIGN(TWOMEG, default_hsize); > npages = size >> self->page_shift; > @@ -1606,7 +1557,7 @@ TEST_F(hmm, compound) > struct hmm_buffer *buffer; > unsigned long npages; > unsigned long size; > - unsigned long default_hsize; > + unsigned long default_hsize = default_huge_page_size(); > int *ptr; > unsigned char *m; > int ret; > @@ -1614,10 +1565,8 @@ TEST_F(hmm, compound) > > /* Skip test if we can't allocate a hugetlbfs page. */ > > - default_hsize = file_read_ulong("/proc/meminfo", "Hugepagesize:"); > - if (default_hsize < 0 || default_hsize*1024 < default_hsize) > + if (!default_hsize) > SKIP(return, "Huge page size could not be determined"); > - default_hsize = default_hsize*1024; /* KB to B */ > > size = ALIGN(TWOMEG, default_hsize); > npages = size >> self->page_shift; > @@ -2106,7 +2055,7 @@ TEST_F(hmm, migrate_anon_huge_empty) > int *ptr; > int ret; > > - size = TWOMEG; > + size = read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); > @@ -2158,7 +2107,7 @@ TEST_F(hmm, migrate_anon_huge_zero) > int ret; > int val; > > - size = TWOMEG; > + size = read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); > @@ -2221,7 +2170,7 @@ TEST_F(hmm, migrate_anon_huge_free) > int *ptr; > int ret; > > - size = TWOMEG; > + size = read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); > @@ -2280,7 +2229,7 @@ TEST_F(hmm, migrate_anon_huge_fault) > int *ptr; > int ret; > > - size = TWOMEG; > + size = read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); > @@ -2332,7 +2281,7 @@ TEST_F(hmm, migrate_partial_unmap_fault) > { > struct hmm_buffer *buffer; > unsigned long npages; > - unsigned long size = TWOMEG; > + unsigned long size = read_pmd_pagesize(); > unsigned long i; > void *old_ptr; > void *map; > @@ -2398,7 +2347,7 @@ TEST_F(hmm, migrate_remap_fault) > { > struct hmm_buffer *buffer; > unsigned long npages; > - unsigned long size = TWOMEG; > + unsigned long size = read_pmd_pagesize(); > unsigned long i; > void *old_ptr, *new_ptr = NULL; > void *map; Can we please handle the case where read_pmd_pagesize() returns 0, wherever its used? Also, looking at the code, since we are changing size, shouldn’t the offsets[] values in migrate_remap_fault and migrate_partial_unmap_fault be adjusted accordingly? Right now they are fixed at {0, 512KB, 1MB}. > @@ -2498,7 +2447,7 @@ TEST_F(hmm, migrate_anon_huge_err) > int *ptr; > int ret; > > - size = TWOMEG; > + size = read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); > @@ -2593,7 +2542,7 @@ TEST_F(hmm, migrate_anon_huge_zero_err) > int *ptr; > int ret; > > - size = TWOMEG; > + size = read_pmd_pagesize(); > > buffer = malloc(sizeof(*buffer)); > ASSERT_NE(buffer, NULL); While reviewing the code, I noticed that the benchmark_thp_migration testcase also hardcodes the size to 2MB. Can we handle this as well? I’ve updated it to use read_pmd_pagesize(), with a fallback to 2MB if it returns 0. Additionally, I am capping the maximum number of THPs in benchmark tests to avoid integer overflow (e.g., when thp_size * 128 > INT_MAX on 16MB PMD-sized THP systems). Compute the maximum number of THPs at runtime as INT_MAX / thp_size and use the smaller of this value and 128 for the largest benchmark buffer. diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c index 788689497e92..c1c9204dc667 100644 --- a/tools/testing/selftests/mm/hmm-tests.c +++ b/tools/testing/selftests/mm/hmm-tests.c @@ -2756,8 +2756,15 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz TEST_F_TIMEOUT(hmm, benchmark_thp_migration, 120) { struct benchmark_results thp_results, regular_results; - size_t thp_size = 2 * 1024 * 1024; /* 2MB - typical THP size */ + size_t thp_size = read_pmd_pagesize(); int iterations = 5; + size_t max_thps, num_thps; + + if (!thp_size) + thp_size = TWOMEG; + + max_thps = INT_MAX / thp_size; + num_thps = (max_thps > 128) ? 128 : max_thps; printf("\nHMM THP Migration Benchmark\n"); printf("---------------------------\n"); @@ -2765,23 +2772,23 @@ TEST_F_TIMEOUT(hmm, benchmark_thp_migration, 120) /* Test different buffer sizes */ size_t test_sizes[] = { - thp_size / 4, /* 512KB - smaller than THP */ - thp_size / 2, /* 1MB - half THP */ - thp_size, /* 2MB - single THP */ - thp_size * 2, /* 4MB - two THPs */ - thp_size * 4, /* 8MB - four THPs */ - thp_size * 8, /* 16MB - eight THPs */ - thp_size * 128, /* 256MB - one twenty eight THPs */ + thp_size / 4, /* Quarter THP */ + thp_size / 2, /* half THP */ + thp_size, /* single THP */ + thp_size * 2, /* two THPs */ + thp_size * 4, /* four THPs */ + thp_size * 8, /* eight THPs */ + thp_size * num_thps, /* max THPs without overflow */ }; static const char *const test_names[] = { - "Small Buffer (512KB)", - "Half THP Size (1MB)", - "Single THP Size (2MB)", - "Two THP Size (4MB)", - "Four THP Size (8MB)", - "Eight THP Size (16MB)", - "One twenty eight THP Size (256MB)" + "Small Buffer", + "Half THP Size", + "Single THP Size", + "Two THP Size", + "Four THP Size", + "Eight THP Size", + "Large Buffer" }; int num_tests = ARRAY_SIZE(test_sizes); -- Thanks, Sayali