Commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") changes huge=always to allocate THP/mTHP based on write size and split_huge_page_test does not write PMD size data, so file-back THP is not created during the test.
Set /sys/kernel/mm/transparent_hugepage/shmem_enabled to "force" to force THP allocation.
Signed-off-by: Zi Yan ziy@nvidia.com Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com Tested-by: Baolin Wang baolin.wang@linux.alibaba.com --- .../selftests/mm/split_huge_page_test.c | 48 +++++++++++++++++-- 1 file changed, 45 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c index 3f353f3d070f..8e15fc9dce3a 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -264,15 +264,46 @@ void split_pte_mapped_thp(void) void split_file_backed_thp(void) { int status; - int fd; - ssize_t num_written; + int fd, shmem_sysctl_fd; + ssize_t num_written, num_read; char tmpfs_template[] = "/tmp/thp_split_XXXXXX"; const char *tmpfs_loc = mkdtemp(tmpfs_template); - char testfile[INPUT_MAX]; + char testfile[INPUT_MAX], sysctl_buf[INPUT_MAX] = {0}; uint64_t pgoff_start = 0, pgoff_end = 1024; + const char *shmem_sysctl = "/sys/kernel/mm/transparent_hugepage/shmem_enabled"; + char *opt1, *opt2;
ksft_print_msg("Please enable pr_debug in split_huge_pages_in_file() for more info.\n");
+ shmem_sysctl_fd = open(shmem_sysctl, O_RDWR); + if (shmem_sysctl_fd == -1) { + ksft_perror("cannot open shmem sysctl"); + goto out; + } + + num_read = read(shmem_sysctl_fd, sysctl_buf, INPUT_MAX); + if (num_read < 1) { + ksft_perror("Failed to read shmem sysctl"); + goto cleanup_sysctl; + } + + opt1 = strchr(sysctl_buf, '['); + opt2 = strchr(sysctl_buf, ']'); + if (!opt1 || !opt2) { + ksft_perror("cannot read shmem sysctl config"); + goto cleanup_sysctl; + } + + /* get existing shmem sysctl config into sysctl_buf */ + strncpy(sysctl_buf, opt1 + 1, opt2 - opt1 - 1); + memset(sysctl_buf + (opt2 - opt1 - 1), 0, INPUT_MAX); + + num_written = write(shmem_sysctl_fd, "force", sizeof("force")); + if (num_written < 1) { + ksft_perror("Fail to write force to shmem sysctl"); + goto cleanup_sysctl; + } + status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
if (status) @@ -317,13 +348,24 @@ void split_file_backed_thp(void) if (status) ksft_exit_fail_msg("cannot remove tmp dir: %s\n", strerror(errno));
+ num_written = write(shmem_sysctl_fd, sysctl_buf, strlen(sysctl_buf) + 1); + if (num_written < 1) + ksft_perror("Fail to restore shmem sysctl"); + + close(shmem_sysctl_fd); ksft_print_msg("Please check dmesg for more information\n"); ksft_test_result_pass("File-backed THP split test done\n"); return;
cleanup: + num_written = write(shmem_sysctl_fd, sysctl_buf, strlen(sysctl_buf) + 1); + if (num_written < 1) + ksft_perror("Fail to restore shmem sysctl"); umount(tmpfs_loc); rmdir(tmpfs_loc); +cleanup_sysctl: + close(shmem_sysctl_fd); +out: ksft_exit_fail_msg("Error occurred\n"); }
Commit 4d684b5f92ba ("mm: shmem: add large folio support for tmpfs") has added large folio support to shmem. Remove the restriction in split_huge_page*().
Signed-off-by: Zi Yan ziy@nvidia.com Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com --- mm/huge_memory.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3d3ebdc002d5..deb4e72daeb9 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3299,7 +3299,7 @@ static void __split_huge_page(struct page *page, struct list_head *list, /* Some pages can be beyond EOF: drop them from page cache */ if (tail->index >= end) { if (shmem_mapping(folio->mapping)) - nr_dropped++; + nr_dropped += new_nr; else if (folio_test_clear_dirty(tail)) folio_account_cleaned(tail, inode_to_wb(folio->mapping->host)); @@ -3465,12 +3465,6 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, return -EINVAL; } } else if (new_order) { - /* Split shmem folio to non-zero order not supported */ - if (shmem_mapping(folio->mapping)) { - VM_WARN_ONCE(1, - "Cannot split shmem folio to non-0 order"); - return -EINVAL; - } /* * No split if the file system does not support large folio. * Note that we might still have THPs in such mappings due to
On 22.01.25 13:40, Zi Yan wrote:
Commit 4d684b5f92ba ("mm: shmem: add large folio support for tmpfs") has added large folio support to shmem. Remove the restriction in split_huge_page*().
Signed-off-by: Zi Yan ziy@nvidia.com Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com
mm/huge_memory.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3d3ebdc002d5..deb4e72daeb9 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3299,7 +3299,7 @@ static void __split_huge_page(struct page *page, struct list_head *list, /* Some pages can be beyond EOF: drop them from page cache */ if (tail->index >= end) { if (shmem_mapping(folio->mapping))
nr_dropped++;
nr_dropped += new_nr; else if (folio_test_clear_dirty(tail)) folio_account_cleaned(tail, inode_to_wb(folio->mapping->host));@@ -3465,12 +3465,6 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, return -EINVAL; } } else if (new_order) {
/* Split shmem folio to non-zero order not supported */if (shmem_mapping(folio->mapping)) {VM_WARN_ONCE(1,"Cannot split shmem folio to non-0 order");return -EINVAL;}
- No split if the file system does not support large folio.
- Note that we might still have THPs in such mappings due to
Acked-by: David Hildenbrand david@redhat.com
Now split_huge_page*() supports shmem THP split to any lower order. Test it.
The test now reads file content out after split to check if the split corrupts the file data.
Signed-off-by: Zi Yan ziy@nvidia.com Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com Tested-by: Baolin Wang baolin.wang@linux.alibaba.com --- .../selftests/mm/split_huge_page_test.c | 32 ++++++++++++++----- 1 file changed, 24 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c index 8e15fc9dce3a..13ad5ac7d178 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -261,14 +261,16 @@ void split_pte_mapped_thp(void) close(kpageflags_fd); }
-void split_file_backed_thp(void) +void split_file_backed_thp(int order) { int status; int fd, shmem_sysctl_fd; ssize_t num_written, num_read; char tmpfs_template[] = "/tmp/thp_split_XXXXXX"; const char *tmpfs_loc = mkdtemp(tmpfs_template); - char testfile[INPUT_MAX], sysctl_buf[INPUT_MAX] = {0}; + char testfile[INPUT_MAX]; + char sysctl_buf[INPUT_MAX] = {0}; + char file_buf[INPUT_MAX] = {0}; uint64_t pgoff_start = 0, pgoff_end = 1024; const char *shmem_sysctl = "/sys/kernel/mm/transparent_hugepage/shmem_enabled"; char *opt1, *opt2; @@ -314,7 +316,7 @@ void split_file_backed_thp(void) ksft_exit_fail_msg("Fail to create file-backed THP split testing file\n"); }
- fd = open(testfile, O_CREAT|O_WRONLY, 0664); + fd = open(testfile, O_CREAT|O_RDWR, 0664); if (fd == -1) { ksft_perror("Cannot open testing file"); goto cleanup; @@ -322,7 +324,6 @@ void split_file_backed_thp(void)
/* write something to the file, so a file-backed THP can be allocated */ num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1); - close(fd);
if (num_written < 1) { ksft_perror("Fail to write data to testing file"); @@ -330,8 +331,22 @@ void split_file_backed_thp(void) }
/* split the file-backed THP */ - write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, 0); + write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, order); + + /* check file content after split */ + num_read = lseek(fd, 0, SEEK_SET); + if (num_read == -1) { + ksft_perror("Cannot lseek file"); + goto cleanup; + }
+ num_read = read(fd, file_buf, num_written); + if (num_read < 1 || strncmp(file_buf, tmpfs_loc, num_read)) { + ksft_print_msg("File content changed, origin: %s, now: %s\n", tmpfs_loc, file_buf); + goto cleanup; + } + + close(fd); status = unlink(testfile); if (status) { ksft_perror("Cannot remove testing file"); @@ -354,7 +369,7 @@ void split_file_backed_thp(void)
close(shmem_sysctl_fd); ksft_print_msg("Please check dmesg for more information\n"); - ksft_test_result_pass("File-backed THP split test done\n"); + ksft_test_result_pass("File-backed THP split to order %d test done\n", order); return;
cleanup: @@ -523,7 +538,7 @@ int main(int argc, char **argv) if (argc > 1) optional_xfs_path = argv[1];
- ksft_set_plan(1+8+2+9); + ksft_set_plan(1+8+1+9+9);
pagesize = getpagesize(); pageshift = ffs(pagesize) - 1; @@ -540,7 +555,8 @@ int main(int argc, char **argv) split_pmd_thp_to_order(i);
split_pte_mapped_thp(); - split_file_backed_thp(); + for (i = 0; i < 9; i++) + split_file_backed_thp(i);
created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template, &fs_loc);
On 22.01.25 13:40, Zi Yan wrote:
Commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") changes huge=always to allocate THP/mTHP based on write size and split_huge_page_test does not write PMD size data, so file-back THP is not created during the test.
Just curious, why can't we write PMD size data instead, to avoid messing with the "force" option?
On Wed Jan 22, 2025 at 9:26 AM EST, David Hildenbrand wrote:
On 22.01.25 13:40, Zi Yan wrote:
Commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") changes huge=always to allocate THP/mTHP based on write size and split_huge_page_test does not write PMD size data, so file-back THP is not created during the test.
Just curious, why can't we write PMD size data instead, to avoid messing with the "force" option?
It also works. I used "force", because I notice that it is intended for testing. Using it might be more future proof, in case huge=always changes its semantics again in the future.
On 22.01.25 16:16, Zi Yan wrote:
On Wed Jan 22, 2025 at 9:26 AM EST, David Hildenbrand wrote:
On 22.01.25 13:40, Zi Yan wrote:
Commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") changes huge=always to allocate THP/mTHP based on write size and split_huge_page_test does not write PMD size data, so file-back THP is not created during the test.
Just curious, why can't we write PMD size data instead, to avoid messing with the "force" option?
It also works. I used "force", because I notice that it is intended for testing. Using it might be more future proof, in case huge=always changes its semantics again in the future.
I recall discussing with Hugh in an upstream call that "force" is a relict from older times, so naturally I would have just adjusted the test case to trigger the PMD scenario. No strong opinion, though, was just wondering.
On Wed Jan 22, 2025 at 10:27 AM EST, David Hildenbrand wrote:
On 22.01.25 16:16, Zi Yan wrote:
On Wed Jan 22, 2025 at 9:26 AM EST, David Hildenbrand wrote:
On 22.01.25 13:40, Zi Yan wrote:
Commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") changes huge=always to allocate THP/mTHP based on write size and split_huge_page_test does not write PMD size data, so file-back THP is not created during the test.
Just curious, why can't we write PMD size data instead, to avoid messing with the "force" option?
It also works. I used "force", because I notice that it is intended for testing. Using it might be more future proof, in case huge=always changes its semantics again in the future.
I recall discussing with Hugh in an upstream call that "force" is a relict from older times, so naturally I would have just adjusted the test case to trigger the PMD scenario. No strong opinion, though, was just wondering.
Got it. Let me change it and resend. Thank you for the feedback.
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Zi Yan