diff options
Diffstat (limited to 'tools/testing/selftests/kvm/access_tracking_perf_test.c')
| -rw-r--r-- | tools/testing/selftests/kvm/access_tracking_perf_test.c | 281 |
1 files changed, 249 insertions, 32 deletions
diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c index 447e619cf856..da7196fd1b23 100644 --- a/tools/testing/selftests/kvm/access_tracking_perf_test.c +++ b/tools/testing/selftests/kvm/access_tracking_perf_test.c @@ -7,9 +7,11 @@ * This test measures the performance effects of KVM's access tracking. * Access tracking is driven by the MMU notifiers test_young, clear_young, and * clear_flush_young. These notifiers do not have a direct userspace API, - * however the clear_young notifier can be triggered by marking a pages as idle - * in /sys/kernel/mm/page_idle/bitmap. This test leverages that mechanism to - * enable access tracking on guest memory. + * however the clear_young notifier can be triggered either by + * 1. marking a pages as idle in /sys/kernel/mm/page_idle/bitmap OR + * 2. adding a new MGLRU generation using the lru_gen debugfs file. + * This test leverages page_idle to enable access tracking on guest memory + * unless MGLRU is enabled, in which case MGLRU is used. * * To measure performance this test runs a VM with a configurable number of * vCPUs that each touch every page in disjoint regions of memory. Performance @@ -17,10 +19,11 @@ * predefined region. * * Note that a deterministic correctness test of access tracking is not possible - * by using page_idle as it exists today. This is for a few reasons: + * by using page_idle or MGLRU aging as it exists today. This is for a few + * reasons: * - * 1. page_idle only issues clear_young notifiers, which lack a TLB flush. This - * means subsequent guest accesses are not guaranteed to see page table + * 1. page_idle and MGLRU only issue clear_young notifiers, which lack a TLB flush. + * This means subsequent guest accesses are not guaranteed to see page table * updates made by KVM until some time in the future. * * 2. page_idle only operates on LRU pages. Newly allocated pages are not @@ -48,9 +51,17 @@ #include "guest_modes.h" #include "processor.h" +#include "cgroup_util.h" +#include "lru_gen_util.h" + +static const char *TEST_MEMCG_NAME = "access_tracking_perf_test"; + /* Global variable used to synchronize all of the vCPU threads. */ static int iteration; +/* The cgroup memory controller root. Needed for lru_gen-based aging. */ +char cgroup_root[PATH_MAX]; + /* Defines what vCPU threads should do during a given iteration. */ static enum { /* Run the vCPU to access all its memory. */ @@ -65,6 +76,25 @@ static int vcpu_last_completed_iteration[KVM_MAX_VCPUS]; /* Whether to overlap the regions of memory vCPUs access. */ static bool overlap_memory_access; +/* + * If the test should only warn if there are too many idle pages (i.e., it is + * expected). + * -1: Not yet set. + * 0: We do not expect too many idle pages, so FAIL if too many idle pages. + * 1: Having too many idle pages is expected, so merely print a warning if + * too many idle pages are found. + */ +static int idle_pages_warn_only = -1; + +/* Whether or not to use MGLRU instead of page_idle for access tracking */ +static bool use_lru_gen; + +/* Total number of pages to expect in the memcg after touching everything */ +static long test_pages; + +/* Last generation we found the pages in */ +static int lru_gen_last_gen = -1; + struct test_params { /* The backing source for the region of memory. */ enum vm_mem_backing_src_type backing_src; @@ -123,8 +153,24 @@ static void mark_page_idle(int page_idle_fd, uint64_t pfn) "Set page_idle bits for PFN 0x%" PRIx64, pfn); } -static void mark_vcpu_memory_idle(struct kvm_vm *vm, - struct memstress_vcpu_args *vcpu_args) +static void too_many_idle_pages(long idle_pages, long total_pages, int vcpu_idx) +{ + char prefix[18] = {}; + + if (vcpu_idx >= 0) + snprintf(prefix, 18, "vCPU%d: ", vcpu_idx); + + TEST_ASSERT(idle_pages_warn_only, + "%sToo many pages still idle (%lu out of %lu)", + prefix, idle_pages, total_pages); + + printf("WARNING: %sToo many pages still idle (%lu out of %lu), " + "this will affect performance results.\n", + prefix, idle_pages, total_pages); +} + +static void pageidle_mark_vcpu_memory_idle(struct kvm_vm *vm, + struct memstress_vcpu_args *vcpu_args) { int vcpu_idx = vcpu_args->vcpu_idx; uint64_t base_gva = vcpu_args->gva; @@ -177,27 +223,79 @@ static void mark_vcpu_memory_idle(struct kvm_vm *vm, * arbitrary; high enough that we ensure most memory access went through * access tracking but low enough as to not make the test too brittle * over time and across architectures. - * - * When running the guest as a nested VM, "warn" instead of asserting - * as the TLB size is effectively unlimited and the KVM doesn't - * explicitly flush the TLB when aging SPTEs. As a result, more pages - * are cached and the guest won't see the "idle" bit cleared. */ - if (still_idle >= pages / 10) { -#ifdef __x86_64__ - TEST_ASSERT(this_cpu_has(X86_FEATURE_HYPERVISOR), - "vCPU%d: Too many pages still idle (%lu out of %lu)", - vcpu_idx, still_idle, pages); -#endif - printf("WARNING: vCPU%d: Too many pages still idle (%lu out of %lu), " - "this will affect performance results.\n", - vcpu_idx, still_idle, pages); - } + if (still_idle >= pages / 10) + too_many_idle_pages(still_idle, pages, + overlap_memory_access ? -1 : vcpu_idx); close(page_idle_fd); close(pagemap_fd); } +int find_generation(struct memcg_stats *stats, long total_pages) +{ + /* + * For finding the generation that contains our pages, use the same + * 90% threshold that page_idle uses. + */ + int gen = lru_gen_find_generation(stats, total_pages * 9 / 10); + + if (gen >= 0) + return gen; + + if (!idle_pages_warn_only) { + TEST_FAIL("Could not find a generation with 90%% of guest memory (%ld pages).", + total_pages * 9 / 10); + return gen; + } + + /* + * We couldn't find a generation with 90% of guest memory, which can + * happen if access tracking is unreliable. Simply look for a majority + * of pages. + */ + puts("WARNING: Couldn't find a generation with 90% of guest memory. " + "Performance results may not be accurate."); + gen = lru_gen_find_generation(stats, total_pages / 2); + TEST_ASSERT(gen >= 0, + "Could not find a generation with 50%% of guest memory (%ld pages).", + total_pages / 2); + return gen; +} + +static void lru_gen_mark_memory_idle(struct kvm_vm *vm) +{ + struct timespec ts_start; + struct timespec ts_elapsed; + struct memcg_stats stats; + int new_gen; + + /* Make a new generation */ + clock_gettime(CLOCK_MONOTONIC, &ts_start); + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + ts_elapsed = timespec_elapsed(ts_start); + + /* Check the generation again */ + new_gen = find_generation(&stats, test_pages); + + /* + * This function should only be invoked with newly-accessed pages, + * so pages should always move to a newer generation. + */ + if (new_gen <= lru_gen_last_gen) { + /* We did not move to a newer generation. */ + long idle_pages = lru_gen_sum_memcg_stats_for_gen(lru_gen_last_gen, + &stats); + + too_many_idle_pages(min_t(long, idle_pages, test_pages), + test_pages, -1); + } + pr_info("%-30s: %ld.%09lds\n", + "Mark memory idle (lru_gen)", ts_elapsed.tv_sec, + ts_elapsed.tv_nsec); + lru_gen_last_gen = new_gen; +} + static void assert_ucall(struct kvm_vcpu *vcpu, uint64_t expected_ucall) { struct ucall uc; @@ -237,7 +335,7 @@ static void vcpu_thread_main(struct memstress_vcpu_args *vcpu_args) assert_ucall(vcpu, UCALL_SYNC); break; case ITERATION_MARK_IDLE: - mark_vcpu_memory_idle(vm, vcpu_args); + pageidle_mark_vcpu_memory_idle(vm, vcpu_args); break; } @@ -289,15 +387,18 @@ static void access_memory(struct kvm_vm *vm, int nr_vcpus, static void mark_memory_idle(struct kvm_vm *vm, int nr_vcpus) { + if (use_lru_gen) + return lru_gen_mark_memory_idle(vm); + /* * Even though this parallelizes the work across vCPUs, this is still a * very slow operation because page_idle forces the test to mark one pfn - * at a time and the clear_young notifier serializes on the KVM MMU + * at a time and the clear_young notifier may serialize on the KVM MMU * lock. */ pr_debug("Marking VM memory idle (slow)...\n"); iteration_work = ITERATION_MARK_IDLE; - run_iteration(vm, nr_vcpus, "Mark memory idle"); + run_iteration(vm, nr_vcpus, "Mark memory idle (page_idle)"); } static void run_test(enum vm_guest_mode mode, void *arg) @@ -309,11 +410,38 @@ static void run_test(enum vm_guest_mode mode, void *arg) vm = memstress_create_vm(mode, nr_vcpus, params->vcpu_memory_bytes, 1, params->backing_src, !overlap_memory_access); + /* + * If guest_page_size is larger than the host's page size, the + * guest (memstress) will only fault in a subset of the host's pages. + */ + test_pages = params->nr_vcpus * params->vcpu_memory_bytes / + max(memstress_args.guest_page_size, + (uint64_t)getpagesize()); + memstress_start_vcpu_threads(nr_vcpus, vcpu_thread_main); pr_info("\n"); access_memory(vm, nr_vcpus, ACCESS_WRITE, "Populating memory"); + if (use_lru_gen) { + struct memcg_stats stats; + + /* + * Do a page table scan now. Following initial population, aging + * may not cause the pages to move to a newer generation. Do + * an aging pass now so that future aging passes always move + * pages to a newer generation. + */ + printf("Initial aging pass (lru_gen)\n"); + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + TEST_ASSERT(lru_gen_sum_memcg_stats(&stats) >= test_pages, + "Not all pages accounted for (looking for %ld). " + "Was the memcg set up correctly?", test_pages); + access_memory(vm, nr_vcpus, ACCESS_WRITE, "Re-populating memory"); + lru_gen_read_memcg_stats(&stats, TEST_MEMCG_NAME); + lru_gen_last_gen = find_generation(&stats, test_pages); + } + /* As a control, read and write to the populated memory first. */ access_memory(vm, nr_vcpus, ACCESS_WRITE, "Writing to populated memory"); access_memory(vm, nr_vcpus, ACCESS_READ, "Reading from populated memory"); @@ -328,6 +456,37 @@ static void run_test(enum vm_guest_mode mode, void *arg) memstress_destroy_vm(vm); } +static int access_tracking_unreliable(void) +{ +#ifdef __x86_64__ + /* + * When running nested, the TLB size may be effectively unlimited (for + * example, this is the case when running on KVM L0), and KVM doesn't + * explicitly flush the TLB when aging SPTEs. As a result, more pages + * are cached and the guest won't see the "idle" bit cleared. + */ + if (this_cpu_has(X86_FEATURE_HYPERVISOR)) { + puts("Skipping idle page count sanity check, because the test is run nested"); + return 1; + } +#endif + /* + * When NUMA balancing is enabled, guest memory will be unmapped to get + * NUMA faults, dropping the Accessed bits. + */ + if (is_numa_balancing_enabled()) { + puts("Skipping idle page count sanity check, because NUMA balancing is enabled"); + return 1; + } + return 0; +} + +static int run_test_for_each_guest_mode(const char *cgroup, void *arg) +{ + for_each_guest_mode(run_test, arg); + return 0; +} + static void help(char *name) { puts(""); @@ -342,11 +501,22 @@ static void help(char *name) printf(" -v: specify the number of vCPUs to run.\n"); printf(" -o: Overlap guest memory accesses instead of partitioning\n" " them into a separate region of memory for each vCPU.\n"); + printf(" -w: Control whether the test warns or fails if more than 10%%\n" + " of pages are still seen as idle/old after accessing guest\n" + " memory. >0 == warn only, 0 == fail, <0 == auto. For auto\n" + " mode, the test fails by default, but switches to warn only\n" + " if NUMA balancing is enabled or the test detects it's running\n" + " in a VM.\n"); backing_src_help("-s"); puts(""); exit(0); } +void destroy_cgroup(char *cg) +{ + printf("Destroying cgroup: %s\n", cg); +} + int main(int argc, char *argv[]) { struct test_params params = { @@ -354,12 +524,13 @@ int main(int argc, char *argv[]) .vcpu_memory_bytes = DEFAULT_PER_VCPU_MEM_SIZE, .nr_vcpus = 1, }; + char *new_cg = NULL; int page_idle_fd; int opt; guest_modes_append_default(); - while ((opt = getopt(argc, argv, "hm:b:v:os:")) != -1) { + while ((opt = getopt(argc, argv, "hm:b:v:os:w:")) != -1) { switch (opt) { case 'm': guest_modes_cmdline(optarg); @@ -376,6 +547,11 @@ int main(int argc, char *argv[]) case 's': params.backing_src = parse_backing_src_type(optarg); break; + case 'w': + idle_pages_warn_only = + atoi_non_negative("Idle pages warning", + optarg); + break; case 'h': default: help(argv[0]); @@ -383,12 +559,53 @@ int main(int argc, char *argv[]) } } - page_idle_fd = open("/sys/kernel/mm/page_idle/bitmap", O_RDWR); - __TEST_REQUIRE(page_idle_fd >= 0, - "CONFIG_IDLE_PAGE_TRACKING is not enabled"); - close(page_idle_fd); + if (idle_pages_warn_only == -1) + idle_pages_warn_only = access_tracking_unreliable(); + + if (lru_gen_usable()) { + bool cg_created = true; + int ret; - for_each_guest_mode(run_test, ¶ms); + puts("Using lru_gen for aging"); + use_lru_gen = true; + + if (cg_find_controller_root(cgroup_root, sizeof(cgroup_root), "memory")) + ksft_exit_skip("Cannot find memory cgroup controller\n"); + + new_cg = cg_name(cgroup_root, TEST_MEMCG_NAME); + printf("Creating cgroup: %s\n", new_cg); + if (cg_create(new_cg)) { + if (errno == EEXIST) { + printf("Found existing cgroup"); + cg_created = false; + } else { + ksft_exit_skip("could not create new cgroup: %s\n", new_cg); + } + } + + /* + * This will fork off a new process to run the test within + * a new memcg, so we need to properly propagate the return + * value up. + */ + ret = cg_run(new_cg, &run_test_for_each_guest_mode, ¶ms); + if (cg_created) + cg_destroy(new_cg); + if (ret < 0) + TEST_FAIL("child did not spawn or was abnormally killed"); + if (ret) + return ret; + } else { + page_idle_fd = open("/sys/kernel/mm/page_idle/bitmap", O_RDWR); + __TEST_REQUIRE(page_idle_fd >= 0, + "Couldn't open /sys/kernel/mm/page_idle/bitmap. " + "Is CONFIG_IDLE_PAGE_TRACKING enabled?"); + + close(page_idle_fd); + + puts("Using page_idle for aging"); + run_test_for_each_guest_mode(NULL, ¶ms); + } return 0; } |