Add regression and new tests when hugepage has correctable memory errors, and how userspace wants to deal with it: * if enable_soft_offline=1, mapped hugepage is soft offlined * if enable_soft_offline=0, mapped hugepage is intact

Free hugepages case is not explicitly covered by the tests.

Hugepage having corrected memory errors is emulated with MADV_SOFT_OFFLINE.

Acked-by: Miaohe Lin linmiaohe@huawei.com Signed-off-by: Jiaqi Yan jiaqiyan@google.com --- tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 1 + .../selftests/mm/hugetlb-soft-offline.c | 228 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 6 + 4 files changed, 236 insertions(+) create mode 100644 tools/testing/selftests/mm/hugetlb-soft-offline.c

diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore index 0b9ab987601c..064e7b125643 100644 --- a/tools/testing/selftests/mm/.gitignore +++ b/tools/testing/selftests/mm/.gitignore @@ -6,6 +6,7 @@ hugepage-shm hugepage-vmemmap hugetlb-madvise hugetlb-read-hwpoison +hugetlb-soft-offline khugepaged map_hugetlb map_populate diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index 0d96c6123636..e1aa09ddaa3d 100644 --- a/tools/testing/selftests/mm/Makefile +++ b/tools/testing/selftests/mm/Makefile @@ -43,6 +43,7 @@ TEST_GEN_FILES += gup_test TEST_GEN_FILES += hmm-tests TEST_GEN_FILES += hugetlb-madvise TEST_GEN_FILES += hugetlb-read-hwpoison +TEST_GEN_FILES += hugetlb-soft-offline TEST_GEN_FILES += hugepage-mmap TEST_GEN_FILES += hugepage-mremap TEST_GEN_FILES += hugepage-shm diff --git a/tools/testing/selftests/mm/hugetlb-soft-offline.c b/tools/testing/selftests/mm/hugetlb-soft-offline.c new file mode 100644 index 000000000000..f086f0e04756 --- /dev/null +++ b/tools/testing/selftests/mm/hugetlb-soft-offline.c @@ -0,0 +1,228 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Test soft offline behavior for HugeTLB pages: + * - if enable_soft_offline = 0, hugepages should stay intact and soft + * offlining failed with EOPNOTSUPP. + * - if enable_soft_offline = 1, a hugepage should be dissolved and + * nr_hugepages/free_hugepages should be reduced by 1. + * + * Before running, make sure more than 2 hugepages of default_hugepagesz + * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB: + * echo 8 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages + */ + +#define _GNU_SOURCE +#include <errno.h> +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> + +#include <linux/magic.h> +#include <linux/memfd.h> +#include <sys/mman.h> +#include <sys/statfs.h> +#include <sys/types.h> + +#include "../kselftest.h" + +#ifndef MADV_SOFT_OFFLINE +#define MADV_SOFT_OFFLINE 101 +#endif + +#define EPREFIX " !!! " + +static int do_soft_offline(int fd, size_t len, int expect_errno) +{ + char *filemap = NULL; + char *hwp_addr = NULL; + const unsigned long pagesize = getpagesize(); + int ret = 0; + + if (ftruncate(fd, len) < 0) { + ksft_perror(EPREFIX "ftruncate to len failed"); + return -1; + } + + filemap = mmap(NULL, len, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_POPULATE, fd, 0); + if (filemap == MAP_FAILED) { + ksft_perror(EPREFIX "mmap failed"); + ret = -1; + goto untruncate; + } + + memset(filemap, 0xab, len); + ksft_print_msg("Allocated %#lx bytes of hugetlb pages\n", len); + + hwp_addr = filemap + len / 2; + ret = madvise(hwp_addr, pagesize, MADV_SOFT_OFFLINE); + ksft_print_msg("MADV_SOFT_OFFLINE %p ret=%d, errno=%d\n", + hwp_addr, ret, errno); + if (ret != 0) + ksft_perror(EPREFIX "madvise failed"); + + if (errno == expect_errno) + ret = 0; + else { + ksft_print_msg("MADV_SOFT_OFFLINE should ret %d\n", + expect_errno); + ret = -1; + } + + munmap(filemap, len); +untruncate: + if (ftruncate(fd, 0) < 0) + ksft_perror(EPREFIX "ftruncate back to 0 failed"); + + return ret; +} + +static int set_enable_soft_offline(int value) +{ + char cmd[256] = {0}; + FILE *cmdfile = NULL; + + if (value != 0 && value != 1) + return -EINVAL; + + sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value); + cmdfile = popen(cmd, "r"); + + if (cmdfile) + ksft_print_msg("enable_soft_offline => %d\n", value); + else { + ksft_perror(EPREFIX "failed to set enable_soft_offline"); + return errno; + } + + pclose(cmdfile); + return 0; +} + +static int read_nr_hugepages(unsigned long hugepage_size, + unsigned long *nr_hugepages) +{ + char buffer[256] = {0}; + char cmd[256] = {0}; + + sprintf(cmd, "cat /sys/kernel/mm/hugepages/hugepages-%ldkB/nr_hugepages", + hugepage_size); + FILE *cmdfile = popen(cmd, "r"); + + if (cmdfile == NULL) { + ksft_perror(EPREFIX "failed to popen nr_hugepages"); + return -1; + } + + if (!fgets(buffer, sizeof(buffer), cmdfile)) { + ksft_perror(EPREFIX "failed to read nr_hugepages"); + pclose(cmdfile); + return -1; + } + + *nr_hugepages = atoll(buffer); + pclose(cmdfile); + return 0; +} + +static int create_hugetlbfs_file(struct statfs *file_stat) +{ + int fd; + + fd = memfd_create("hugetlb_tmp", MFD_HUGETLB); + if (fd < 0) { + ksft_perror(EPREFIX "could not open hugetlbfs file"); + return -1; + } + + memset(file_stat, 0, sizeof(*file_stat)); + if (fstatfs(fd, file_stat)) { + ksft_perror(EPREFIX "fstatfs failed"); + goto close; + } + if (file_stat->f_type != HUGETLBFS_MAGIC) { + ksft_print_msg(EPREFIX "not hugetlbfs file\n"); + goto close; + } + + return fd; +close: + close(fd); + return -1; +} + +static void test_soft_offline_common(int enable_soft_offline) +{ + int fd; + int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP; + struct statfs file_stat; + unsigned long hugepagesize_kb = 0; + unsigned long nr_hugepages_before = 0; + unsigned long nr_hugepages_after = 0; + int ret; + + ksft_print_msg("Test soft-offline when enabled_soft_offline=%d\n", + enable_soft_offline); + + fd = create_hugetlbfs_file(&file_stat); + if (fd < 0) + ksft_exit_fail_msg("Failed to create hugetlbfs file\n"); + + hugepagesize_kb = file_stat.f_bsize / 1024; + ksft_print_msg("Hugepagesize is %ldkB\n", hugepagesize_kb); + + if (set_enable_soft_offline(enable_soft_offline) != 0) { + close(fd); + ksft_exit_fail_msg("Failed to set enable_soft_offline\n"); + } + + if (read_nr_hugepages(hugepagesize_kb, &nr_hugepages_before) != 0) { + close(fd); + ksft_exit_fail_msg("Failed to read nr_hugepages\n"); + } + + ksft_print_msg("Before MADV_SOFT_OFFLINE nr_hugepages=%ld\n", + nr_hugepages_before); + + ret = do_soft_offline(fd, 2 * file_stat.f_bsize, expect_errno); + + if (read_nr_hugepages(hugepagesize_kb, &nr_hugepages_after) != 0) { + close(fd); + ksft_exit_fail_msg("Failed to read nr_hugepages\n"); + } + + ksft_print_msg("After MADV_SOFT_OFFLINE nr_hugepages=%ld\n", + nr_hugepages_after); + + // No need for the hugetlbfs file from now on. + close(fd); + + if (enable_soft_offline) { + if (nr_hugepages_before != nr_hugepages_after + 1) { + ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n"); + return; + } + } else { + if (nr_hugepages_before != nr_hugepages_after) { + ksft_test_result_fail("MADV_SOFT_OFFLINE reduced %lu hugepages\n", + nr_hugepages_before - nr_hugepages_after); + return; + } + } + + ksft_test_result(ret == 0, + "Test soft-offline when enabled_soft_offline=%d\n", + enable_soft_offline); +} + +int main(int argc, char **argv) +{ + ksft_print_header(); + ksft_set_plan(2); + + test_soft_offline_common(1); + test_soft_offline_common(0); + + ksft_finished(); +} diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh index 5698d519170d..03ac4f2e1cce 100755 --- a/tools/testing/selftests/mm/run_vmtests.sh +++ b/tools/testing/selftests/mm/run_vmtests.sh @@ -332,6 +332,12 @@ CATEGORY="hugetlb" run_test ./thuge-gen CATEGORY="hugetlb" run_test ./charge_reserved_hugetlb.sh -cgroup-v2 CATEGORY="hugetlb" run_test ./hugetlb_reparenting_test.sh -cgroup-v2 if $RUN_DESTRUCTIVE; then +nr_hugepages_tmp=$(cat /proc/sys/vm/nr_hugepages) +enable_soft_offline=$(cat /proc/sys/vm/enable_soft_offline) +echo 8 > /proc/sys/vm/nr_hugepages +CATEGORY="hugetlb" run_test ./hugetlb-soft-offline +echo "$nr_hugepages_tmp" > /proc/sys/vm/nr_hugepages +echo "$enable_soft_offline" > /proc/sys/vm/enable_soft_offline CATEGORY="hugetlb" run_test ./hugetlb-read-hwpoison fi

Add the documentation for soft offline behaviors / costs, and what the new enable_soft_offline sysctl is for.

Acked-by: Oscar Salvador osalvador@suse.de Acked-by: Miaohe Lin linmiaohe@huawei.com Signed-off-by: Jiaqi Yan jiaqiyan@google.com --- Documentation/admin-guide/sysctl/vm.rst | 32 +++++++++++++++++++++++++ 1 file changed, 32 insertions(+)

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index e86c968a7a0e..75e22137d849 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -36,6 +36,7 @@ Currently, these files are in /proc/sys/vm: - dirtytime_expire_seconds - dirty_writeback_centisecs - drop_caches +- enable_soft_offline - extfrag_threshold - highmem_is_dirtyable - hugetlb_shm_group @@ -267,6 +268,37 @@ used:: These are informational only. They do not mean that anything is wrong with your system. To disable them, echo 4 (bit 2) into drop_caches.

+enable_soft_offline +=================== +Correctable memory errors are very common on servers. Soft-offline is kernel's +solution for memory pages having (excessive) corrected memory errors. + +For different types of page, soft-offline has different behaviors / costs. +- For a raw error page, soft-offline migrates the in-use page's content to + a new raw page. +- For a page that is part of a transparent hugepage, soft-offline splits the + transparent hugepage into raw pages, then migrates only the raw error page. + As a result, user is transparently backed by 1 less hugepage, impacting + memory access performance. +- For a page that is part of a HugeTLB hugepage, soft-offline first migrates + the entire HugeTLB hugepage, during which a free hugepage will be consumed + as migration target. Then the original hugepage is dissolved into raw + pages without compensation, reducing the capacity of the HugeTLB pool by 1. + +It is user's call to choose between reliability (staying away from fragile +physical memory) vs performance / capacity implications in transparent and +HugeTLB cases. + +For all architectures, enable_soft_offline controls whether to soft offline +memory pages. When set to 1, kernel attempts to soft offline the pages +whenever it thinks needed. When set to 0, kernel returns EOPNOTSUPP to +the request to soft offline the pages. Its default value is 1. + +It is worth mentioning that after setting enable_soft_offline to 0, the +following requests to soft offline pages will not be performed: +- Request to soft offline pages from RAS Correctable Errors Collector. +- On ARM, the request to soft offline pages from GHES driver. +- On PARISC, the request to soft offline pages from Page Deallocation Table.

extfrag_threshold =================