From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1895223C368; Mon, 24 Aug 2026 09:35:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787564139; cv=none; b=f/epOGGkxSn6tGawsvzeFhaT08MjSwCGGxycBrBdhaPTjXacvVRUMFS9AMHbei/WWrli8tx0BT1fS+NL23fr0xj+RaPu+wG9N1ItnFTcfV5z8Owc9Qs2K8xpAuHPXUnzlWSR/J0fQw+DaRyAHrU0knoimNLUkSQggEQrdqIc+J0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787564139; c=relaxed/simple; bh=x2XWodpi7c705kOimdSZSK/CELysuaMs/Fe2Jg8/SV8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=p3CUq0/JMyCVVutvp9S9R862YJQKOceYILRKJnl+RJxgnc+OytmN0Qe4l4eM3My4f7kjRHesgAb3uteMeRsoR7XWqE2Wkr8IlKGjHvaLwxe5Q6KmvjGhsmghzhNQas7uSZskVGSXLMLS6JqLVc9kMSAO2xA2beeWpXSCgHXA17k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=b9R0KcV8; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="b9R0KcV8" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 658D0169C; Mon, 24 Aug 2026 02:35:32 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6B2643F66F; Mon, 24 Aug 2026 02:35:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1787564136; bh=x2XWodpi7c705kOimdSZSK/CELysuaMs/Fe2Jg8/SV8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b9R0KcV88ObXNWwaJXvJ/+E1cxsVdf4Lu/wt6+byMfBPZhmfFY5c5ZZdvlbH5ttCT 4ERMCTbHqz69qFn/6tyOkOgkah5oPEScb19gJ5oh0FqhIrRgCwumeJSBFxDPORc7Yn cfgERelErZMX6ZRyeobV404gDFiNbhZGO8GRoDZI= Date: Mon, 24 Aug 2026 10:35:31 +0100 From: Yeoreum Yun To: Dev Jain Cc: Yeoreum Yun , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Message-ID: References: <20260820-fix_split-v1-0-ab430c58c7cf@arm.com> <20260820-fix_split-v1-2-ab430c58c7cf@arm.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: > > > On 21/08/26 1:10 am, Yeoreum Yun wrote: > > Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on AArch64”), > > glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations > > made by memalign(). > > > > The underlying VMA may start at a different address from the aligned > > address returned by memalign(). Furthermore, a subsequent > > madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is > > already set. > > Replying to this because I saw my malloc commit pop up :) > > So IIUC the test is dependent on VMA boundaries. Therefore we shouldn't > rely on a glibc function like memalign() which can do anything internally. > > I think in this case memalign is using one of the heaps, which reuses > VMAs. Because I would expect mmap() to internally align the VMA start > to 2M, as we handle this as a special case in kernel mmap code. I'm not aware of memalign() behavior detail, but It doesn't seems to resue the VMA area: - whlie memalign() (request 8MB): mmap(NULL, 10489856, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xed1b4557f000 madvise(0xed1b4557f000, 10489856, MADV_HUGEPAGE) = 0 - at split_huge_page_test after memalign() while making THP: madvise(0xed1b45600000, 8388608, MADV_HUGEPAGE) = 0 It seems memalign() adds a front padding internally and calls madvise() with MADV_HUGEPAGE then return aldigned address inside of memalign() not depends on mmap() behavior. > > > > > This causes split_huge_page_test to fail because the check_huge_xxx() > > helpers incorrectly require the address returned by memalign() to > > match the VMA start address reported in /proc/self/smaps. > > > > Fix this by using /proc/self/pagemap and /proc/kpageflags instead of > > /proc/self/smaps to detect huge pages and change the meaning of > > check_huge_xxx()'s nr_hpages argument: > > > > - nr_hpages > 0: check all of pages in the range are huge page. > > - nr_hpages < 0: check all of pages in the range are not huge page. > > - nr_hpages == 0: invalid. > > > > Reported-by: David Hildenbrand (Arm) > > Signed-off-by: Yeoreum Yun > > --- > > tools/testing/selftests/mm/khugepaged.c | 26 ++--- > > tools/testing/selftests/mm/split_huge_page_test.c | 6 +- > > tools/testing/selftests/mm/vm_util.c | 135 ++++++++++++++++++---- > > tools/testing/selftests/mm/vm_util.h | 1 + > > 4 files changed, 131 insertions(+), 37 deletions(-) > > > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c > > index 10e8dedcb087d..2e4665e6d5852 100644 > > --- a/tools/testing/selftests/mm/khugepaged.c > > +++ b/tools/testing/selftests/mm/khugepaged.c > > @@ -533,7 +533,7 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages, > > ret = madvise_collapse_retry(p, nr_hpages * hpage_pmd_size); > > if (((bool)ret) == expect) > > fail("Fail: Bad return value"); > > - else if (!ops->check_huge(p, expect ? nr_hpages : 0)) > > + else if (!ops->check_huge(p, expect ? nr_hpages : -nr_hpages)) > > fail("Fail: check_huge()"); > > else > > success("OK"); > > @@ -545,7 +545,7 @@ static void madvise_collapse(const char *msg, char *p, int nr_hpages, > > struct mem_ops *ops, bool expect) > > { > > /* Sanity check */ > > - if (!ops->check_huge(p, 0)) > > + if (!ops->check_huge(p, -nr_hpages)) > > ksft_exit_fail_msg("Unexpected huge page\n"); > > __madvise_collapse(msg, p, nr_hpages, ops, expect); > > } > > @@ -558,7 +558,7 @@ static bool wait_for_scan(const char *msg, char *p, int nr_hpages, > > int timeout = 6; /* 3 seconds */ > > > > /* Sanity check */ > > - if (!ops->check_huge(p, 0)) > > + if (!ops->check_huge(p, -nr_hpages)) > > ksft_exit_fail_msg("Unexpected huge page\n"); > > > > madvise(p, nr_hpages * hpage_pmd_size, MADV_HUGEPAGE); > > @@ -605,7 +605,7 @@ static void khugepaged_collapse(const char *msg, char *p, int nr_hpages, > > if (ops != &__anon_ops) > > ops->fault(p, 0, nr_hpages * hpage_pmd_size); > > > > - if (ops->check_huge(p, expect ? nr_hpages : 0)) > > + if (ops->check_huge(p, expect ? nr_hpages : -nr_hpages)) > > success("OK"); > > else > > fail("Fail"); > > @@ -643,7 +643,7 @@ static void alloc_at_fault(void) > > > > madvise(p, page_size, MADV_DONTNEED); > > ksft_print_msg("Split huge PMD on MADV_DONTNEED..."); > > - if (check_huge_anon(p, 0, hpage_pmd_size)) > > + if (check_huge_anon(p, -1, hpage_pmd_size)) > > success("OK"); > > else > > fail("Fail"); > > @@ -815,7 +815,7 @@ static void collapse_single_pte_entry_compound(struct collapse_context *c, struc > > madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE); > > ksft_print_msg("Split huge page leaving single PTE mapping compound page..."); > > madvise(p + page_size, hpage_pmd_size - page_size, MADV_DONTNEED); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -836,7 +836,7 @@ static void collapse_full_of_compound(struct collapse_context *c, struct mem_ops > > ksft_print_msg("Split huge page leaving single PTE page table full of compound pages..."); > > madvise(p, page_size, MADV_NOHUGEPAGE); > > madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -903,7 +903,7 @@ static void collapse_fork(struct collapse_context *c, struct mem_ops *ops) > > > > ksft_print_msg("Allocate small page..."); > > ops->fault(p, 0, page_size); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -911,7 +911,7 @@ static void collapse_fork(struct collapse_context *c, struct mem_ops *ops) > > ksft_print_msg("Share small page over fork()..."); > > if (!fork()) { > > /* Do not touch settings on child exit */ > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -929,7 +929,7 @@ static void collapse_fork(struct collapse_context *c, struct mem_ops *ops) > > exit_status = WEXITSTATUS(wstatus); > > > > ksft_print_msg("Check if parent still has small page..."); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -955,7 +955,7 @@ static void collapse_fork_compound(struct collapse_context *c, struct mem_ops *o > > ksft_print_msg("Split huge page PMD in child process..."); > > madvise(p, page_size, MADV_NOHUGEPAGE); > > madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -1003,7 +1003,7 @@ static void collapse_max_ptes_shared(struct collapse_context *c, struct mem_ops > > ksft_print_msg("Trigger CoW on page %d of %d...", > > hpage_pmd_nr - max_ptes_shared - 1, hpage_pmd_nr); > > ops->fault(p, 0, (hpage_pmd_nr - max_ptes_shared - 1) * page_size); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > @@ -1016,7 +1016,7 @@ static void collapse_max_ptes_shared(struct collapse_context *c, struct mem_ops > > hpage_pmd_nr - max_ptes_shared, hpage_pmd_nr); > > ops->fault(p, 0, (hpage_pmd_nr - max_ptes_shared) * > > page_size); > > - if (ops->check_huge(p, 0)) > > + if (ops->check_huge(p, -1)) > > success("OK"); > > else > > fail("Fail"); > > diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c > > index 99b45e5518199..4fcd330cf0726 100644 > > --- a/tools/testing/selftests/mm/split_huge_page_test.c > > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > > @@ -314,7 +314,7 @@ static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hp > > if (one_page[i] != (char)0) > > ksft_exit_fail_msg("%ld byte corrupted\n", i); > > > > - if (!check_huge_anon(one_page, 0, pmd_pagesize)) > > + if (!check_huge_anon(one_page, -nr_hpages, pmd_pagesize)) > > ksft_exit_fail_msg("Still AnonHugePages not split\n"); > > > > rss_anon_after = rss_anon(); > > @@ -372,7 +372,7 @@ static void split_pmd_thp_to_order(int order) > > (pmd_order + 1))) > > ksft_exit_fail_msg("Unexpected THP split\n"); > > > > - if (!check_huge_anon(one_page, 0, pmd_pagesize)) > > + if (!check_huge_anon(one_page, -4, pmd_pagesize)) > > ksft_exit_fail_msg("Still AnonHugePages not split\n"); > > > > ksft_test_result_pass("Split huge pages to order %d successful\n", order); > > @@ -746,7 +746,7 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size, > > goto out; > > } > > > > - if (!check_huge_file(addr, 0, pmd_pagesize)) { > > + if (!check_huge_file(addr, -(fd_size / pmd_pagesize), pmd_pagesize)) { > > ksft_print_msg("Still FilePmdMapped not split\n"); > > err = EXIT_FAILURE; > > goto out; > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > > index 311fc5b4513eb..166d5d79289f3 100644 > > --- a/tools/testing/selftests/mm/vm_util.c > > +++ b/tools/testing/selftests/mm/vm_util.c > > @@ -14,6 +14,8 @@ > > #define PMD_SIZE_FILE_PATH "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size" > > #define SMAP_FILE_PATH "/proc/self/smaps" > > #define STATUS_FILE_PATH "/proc/self/status" > > +#define PAGEMAP_FILE_PATH "/proc/self/pagemap" > > +#define KPAGEFLAGS_FILE_PATH "/proc/kpageflags" > > #define MAX_LINE_LENGTH 500 > > > > unsigned int __page_size; > > @@ -229,37 +231,128 @@ char *__get_smap_entry(void *addr, const char *pattern, char *buf, size_t len) > > return entry; > > } > > > > -bool __check_huge(void *addr, char *pattern, int nr_hpages, > > - uint64_t hpage_size) > > -{ > > - char buffer[MAX_LINE_LENGTH]; > > - uint64_t thp = -1; > > - char *entry; > > - > > - entry = __get_smap_entry(addr, pattern, buffer, sizeof(buffer)); > > - if (!entry) > > - goto err_out; > > - > > - if (sscanf(entry, "%9" SCNu64 " kB", &thp) != 1) > > - ksft_exit_fail_msg("Reading smap error\n"); > > - > > -err_out: > > - return thp == (nr_hpages * (hpage_size >> 10)); > > -} > > - > > bool check_huge_anon(void *addr, int nr_hpages, uint64_t hpage_size) > > { > > - return __check_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size); > > + int i, pagemap_fd, nr = 0; > > + uint64_t categories; > > + bool expect_huge; > > + > > + if (nr_hpages == 0 || hpage_size == 0) > > + return false; > > + > > + if (nr_hpages < 0) { > > + nr_hpages = -nr_hpages; > > + expect_huge = false; > > + } else > > + expect_huge = true; > > + > > + pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY); > > + if (pagemap_fd < 0) > > + ksft_exit_fail_msg("open pagemap: %s\n", strerror(errno)); > > + > > + for (i = 0; i < nr_hpages; i++, addr += hpage_size) { > > + categories = pagemap_scan_get_categories(pagemap_fd, addr); > > + if (!(categories & PAGE_IS_HUGE)) > > + continue; > > + if (categories & PAGE_IS_FILE) > > + continue; > > + nr++; > > + } > > + > > + close(pagemap_fd); > > + return expect_huge ? nr == nr_hpages : nr == 0; > > } > > > > bool check_huge_file(void *addr, int nr_hpages, uint64_t hpage_size) > > { > > - return __check_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); > > + int i, pagemap_fd, kpf_fd, nr = 0; > > + unsigned long pfn; > > + uint64_t categories, kpf; > > + bool expect_huge; > > + > > + if (nr_hpages == 0 || hpage_size == 0) > > + return false; > > + > > + if (nr_hpages < 0) { > > + nr_hpages = -nr_hpages; > > + expect_huge = false; > > + } else > > + expect_huge = true; > > + > > + pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY); > > + if (pagemap_fd < 0) > > + ksft_exit_fail_msg("open pagemap: %s\n", strerror(errno)); > > + > > + kpf_fd = open(KPAGEFLAGS_FILE_PATH, O_RDONLY); > > + if (kpf_fd < 0) > > + ksft_exit_fail_msg("open kpageflags: %s\n", strerror(errno)); > > + > > + for (i = 0; i < nr_hpages; i++, addr += hpage_size) { > > + categories = pagemap_scan_get_categories(pagemap_fd, addr); > > + pfn = pagemap_get_pfn(pagemap_fd, addr); > > + if (pfn == -1UL) > > + continue; > > + if (pageflags_get(pfn, kpf_fd, &kpf)) > > + ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno)); > > + if (!(categories & PAGE_IS_HUGE)) > > + continue; > > + if (!(categories & PAGE_IS_FILE)) > > + continue; > > + if (kpf & KPF_SWAPBACKED) > > + continue; > > + nr++; > > + } > > + > > + close(pagemap_fd); > > + close(kpf_fd); > > + > > + return expect_huge ? nr == nr_hpages : nr == 0; > > } > > > > bool check_huge_shmem(void *addr, int nr_hpages, uint64_t hpage_size) > > { > > - return __check_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size); > > + int i, pagemap_fd, kpf_fd, nr = 0; > > + unsigned long pfn; > > + uint64_t categories, kpf; > > + bool expect_huge; > > + > > + if (nr_hpages == 0 || hpage_size == 0) > > + return false; > > + > > + if (nr_hpages < 0) { > > + nr_hpages = -nr_hpages; > > + expect_huge = true; > > + } else > > + expect_huge = false; > > + > > + pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY); > > + if (pagemap_fd < 0) > > + ksft_exit_fail_msg("open pagemap: %s\n", strerror(errno)); > > + > > + kpf_fd = open(KPAGEFLAGS_FILE_PATH, O_RDONLY); > > + if (kpf_fd < 0) > > + ksft_exit_fail_msg("open kpageflags: %s\n", strerror(errno)); > > + > > + for (i = 0; i < nr_hpages; i++, addr += hpage_size) { > > + categories = pagemap_scan_get_categories(pagemap_fd, addr); > > + pfn = pagemap_get_pfn(pagemap_fd, addr); > > + if (pfn == -1UL) > > + continue; > > + if (pageflags_get(pfn, kpf_fd, &kpf)) > > + ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno)); > > + if (!(categories & PAGE_IS_HUGE)) > > + continue; > > + if (!(categories & PAGE_IS_FILE)) > > + continue; > > + if (!(kpf & KPF_SWAPBACKED)) > > + continue; > > + nr++; > > + } > > + > > + close(pagemap_fd); > > + close(kpf_fd); > > + > > + return expect_huge ? nr == nr_hpages : nr == 0; > > } > > > > int64_t allocate_transhuge(void *ptr, int pagemap_fd) > > diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h > > index ea8fc8fdf0eb0..0a1627f36efc3 100644 > > --- a/tools/testing/selftests/mm/vm_util.h > > +++ b/tools/testing/selftests/mm/vm_util.h > > @@ -18,6 +18,7 @@ > > #define PM_SWAP BIT_ULL(62) > > #define PM_PRESENT BIT_ULL(63) > > > > +#define KPF_SWAPBACKED BIT_ULL(14) > > #define KPF_COMPOUND_HEAD BIT_ULL(15) > > #define KPF_COMPOUND_TAIL BIT_ULL(16) > > #define KPF_HWPOISON BIT_ULL(19) > > > -- Sincerely, Yeoreum Yun