From patchwork Wed Jun 30 21:48:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Matlack X-Patchwork-Id: 12352843 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB0DBC11F68 for ; Wed, 30 Jun 2021 21:48:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C4FCE61474 for ; Wed, 30 Jun 2021 21:48:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232604AbhF3VvG (ORCPT ); Wed, 30 Jun 2021 17:51:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232748AbhF3Vu7 (ORCPT ); Wed, 30 Jun 2021 17:50:59 -0400 Received: from mail-qk1-x749.google.com (mail-qk1-x749.google.com [IPv6:2607:f8b0:4864:20::749]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED6CAC061756 for ; Wed, 30 Jun 2021 14:48:29 -0700 (PDT) Received: by mail-qk1-x749.google.com with SMTP id n195-20020a3740cc0000b02903b2ccb7bbe6so2683529qka.20 for ; Wed, 30 Jun 2021 14:48:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=+uiwqEz6p8XQTY9ZsTXgjKWNLycVEoinELUzv5S6vDA=; b=jjg1kjgPluwrJVeE1wLEt6avxIIZZb2VkKJViCPN5AMr1Pon+SkvZno8Agy5776Rj9 Vrt2Bl8wVHODMwO6RSE7RoMyIDlzFx0d4QdsR6Y6zkbYunKWiN0uyDy5nQJnMrhiKWKC IGWAuDdPM5x/9SddyB8AgSB7JJj8vz59G+HyKgO00z/3hs5ENFU6NWQK9QeFzXRVE76T fnoQQcmtG9tdNevd22s+8WNSFTTgQY4xSM340iGiJ6L2f8IyvSeHfsOe1IiH99MZiCyb 9HJXdfjqf9fKUPtyhpTjXgiNCCztn93wu6lJHnkKlLxI7SD7GUMaNvwCy4YZunR1X/Zn QFTg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=+uiwqEz6p8XQTY9ZsTXgjKWNLycVEoinELUzv5S6vDA=; b=OcIbiyVHLZv2e88YkR2nsnNnUYrjHxil37ObwWRw9jL4TsUbnNf04MnmTWGh6n5b6C rCy+Mgcw2voBLyKKTYLVc+2KUNN28mCwDyH+jtuw/bRji6pAUYric/ra7KGkaXtSW71y baxGq9byMC/6HLBWEgwXMjrif2BxQNVnPAxaUkJAO36v1y3orBXgOSBMukuhxIL3CVbd /BbSKieQ53szV6xARcGbvHINnjrGQgNnrHkhcagvfpU8StpMnUU4fKBDcGD2VKZirmxQ yKt1hEaYLVQoFoG8tja+1XtdHRPTcmykbDS/6F+qMnHBVFhFWpLD3M2l+IeT6uNasaHF HZNw== X-Gm-Message-State: AOAM5338KNHGc3TCEXd5pAai48ZTSF1MghouknTWdl9QzOQTIpoIsxHZ 6YNibYKI69Vw6PlMrK17UTJcRo5HsA9DpefFBE8Y+FSVsBvt0I6GrH067H6myx8MwCksbIV40nH NuPUGiDWKLzh1WJliGbvV6rC5aTG0Uj/rVQzw/UFAI70wTy/+ChqVgGs0a8ZdLZQ= X-Google-Smtp-Source: ABdhPJy3p+PnDzIJcDAiu8PHnHxGEp++zQQx+BrWmL9jqHqprsxl2GqJ2ZsTw7qWFZI7OQ6ybnrtHLTLgGsJ9Q== X-Received: from dmatlack-heavy.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:19cd]) (user=dmatlack job=sendgmr) by 2002:a05:6214:8c4:: with SMTP id da4mr15901615qvb.3.1625089708935; Wed, 30 Jun 2021 14:48:28 -0700 (PDT) Date: Wed, 30 Jun 2021 21:48:02 +0000 In-Reply-To: <20210630214802.1902448-1-dmatlack@google.com> Message-Id: <20210630214802.1902448-7-dmatlack@google.com> Mime-Version: 1.0 References: <20210630214802.1902448-1-dmatlack@google.com> X-Mailer: git-send-email 2.32.0.93.g670b81a890-goog Subject: [PATCH v2 6/6] KVM: selftests: Introduce access_tracking_perf_test From: David Matlack To: kvm@vger.kernel.org Cc: Ben Gardon , Joerg Roedel , Jim Mattson , Wanpeng Li , Vitaly Kuznetsov , Sean Christopherson , Paolo Bonzini , Junaid Shahid , Andrew Jones , Matthew Wilcox , Yu Zhao , David Hildenbrand , Andrew Morton , David Matlack Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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. 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 is measured in the time it takes all vCPUs to finish touching their predefined region. Example invocation: $ ./access_tracking_perf_test -v 8 Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages guest physical test memory offset: 0xffdfffff000 Populating memory : 1.337752570s Writing to populated memory : 0.010177640s Reading from populated memory : 0.009548239s Mark memory idle : 23.973131748s Writing to idle memory : 0.063584496s Mark memory idle : 24.924652964s Reading from idle memory : 0.062042814s Breaking down the results: * "Populating memory": The time it takes for all vCPUs to perform the first write to every page in their region. * "Writing to populated memory" / "Reading from populated memory": The time it takes for all vCPUs to write and read to every page in their region after it has been populated. This serves as a control for the later results. * "Mark memory idle": The time it takes for every vCPU to mark every page in their region as idle through page_idle. * "Writing to idle memory" / "Reading from idle memory": The time it takes for all vCPUs to write and read to every page in their region after it has been marked idle. This test should be portable across architectures but it is only enabled for x86_64 since that's all I have tested. Reviewed-by: Ben Gardon Signed-off-by: David Matlack --- tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/access_tracking_perf_test.c | 429 ++++++++++++++++++ 3 files changed, 431 insertions(+) create mode 100644 tools/testing/selftests/kvm/access_tracking_perf_test.c diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore index d5bc9bf3b528..e16cbe7b9ce3 100644 --- a/tools/testing/selftests/kvm/.gitignore +++ b/tools/testing/selftests/kvm/.gitignore @@ -38,6 +38,7 @@ /x86_64/xen_vmcall_test /x86_64/xss_msr_test /x86_64/vmx_pmu_msrs_test +/access_tracking_perf_test /demand_paging_test /dirty_log_test /dirty_log_perf_test diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index bc65c57ae40d..e1ce404f3c67 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -71,6 +71,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/tsc_msrs_test TEST_GEN_PROGS_x86_64 += x86_64/vmx_pmu_msrs_test TEST_GEN_PROGS_x86_64 += x86_64/xen_shinfo_test TEST_GEN_PROGS_x86_64 += x86_64/xen_vmcall_test +TEST_GEN_PROGS_x86_64 += access_tracking_perf_test TEST_GEN_PROGS_x86_64 += demand_paging_test TEST_GEN_PROGS_x86_64 += dirty_log_test TEST_GEN_PROGS_x86_64 += dirty_log_perf_test diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c new file mode 100644 index 000000000000..e2baa187a21e --- /dev/null +++ b/tools/testing/selftests/kvm/access_tracking_perf_test.c @@ -0,0 +1,429 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * access_tracking_perf_test + * + * Copyright (C) 2021, Google, Inc. + * + * 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. + * + * 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 + * is measured in the time it takes all vCPUs to finish touching their + * 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: + * + * 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 + * updates made by KVM until some time in the future. + * + * 2. page_idle only operates on LRU pages. Newly allocated pages are not + * immediately allocated to LRU lists. Instead they are held in a "pagevec", + * which is drained to LRU lists some time in the future. There is no + * userspace API to force this drain to occur. + * + * These limitations are worked around in this test by using a large enough + * region of memory for each vCPU such that the number of translations cached in + * the TLB and the number of pages held in pagevecs are a small fraction of the + * overall workload. And if either of those conditions are not true this test + * will fail rather than silently passing. + */ +#include +#include +#include +#include +#include +#include + +#include "kvm_util.h" +#include "test_util.h" +#include "perf_test_util.h" +#include "guest_modes.h" + +/* Global variable used to synchronize all of the vCPU threads. */ +static int iteration = -1; + +/* Defines what vCPU threads should do during a given iteration. */ +static enum { + /* Run the vCPU to access all its memory. */ + ITERATION_ACCESS_MEMORY, + /* Mark the vCPU's memory idle in page_idle. */ + ITERATION_MARK_IDLE, +} iteration_work; + +/* Set to true when vCPU threads should exit. */ +static bool done; + +/* The iteration that was last completed by each vCPU. */ +static int vcpu_last_completed_iteration[KVM_MAX_VCPUS]; + +/* Whether to overlap the regions of memory vCPUs access. */ +static bool overlap_memory_access; + +struct test_params { + /* The backing source for the region of memory. */ + enum vm_mem_backing_src_type backing_src; + + /* The amount of memory to allocate for each vCPU. */ + uint64_t vcpu_memory_bytes; + + /* The number of vCPUs to create in the VM. */ + int vcpus; +}; + +static uint64_t pread_uint64(int fd, const char *filename, uint64_t index) +{ + uint64_t value; + off_t offset = index * sizeof(value); + + TEST_ASSERT(pread(fd, &value, sizeof(value), offset) == sizeof(value), + "pread from %s offset 0x%" PRIx64 " failed!", + filename, offset); + + return value; + +} + +#define PAGEMAP_PRESENT (1ULL << 63) +#define PAGEMAP_PFN_MASK ((1ULL << 55) - 1) + +static uint64_t lookup_pfn(int pagemap_fd, struct kvm_vm *vm, uint64_t gva) +{ + uint64_t hva = (uint64_t) addr_gva2hva(vm, gva); + uint64_t entry; + uint64_t pfn; + + entry = pread_uint64(pagemap_fd, "pagemap", hva / getpagesize()); + if (!(entry & PAGEMAP_PRESENT)) + return 0; + + pfn = entry & PAGEMAP_PFN_MASK; + if (!pfn) { + print_skip("Looking up PFNs requires CAP_SYS_ADMIN"); + exit(KSFT_SKIP); + } + + return pfn; +} + +static bool is_page_idle(int page_idle_fd, uint64_t pfn) +{ + uint64_t bits = pread_uint64(page_idle_fd, "page_idle", pfn / 64); + + return !!((bits >> (pfn % 64)) & 1); +} + +static void mark_page_idle(int page_idle_fd, uint64_t pfn) +{ + uint64_t bits = 1ULL << (pfn % 64); + + TEST_ASSERT(pwrite(page_idle_fd, &bits, 8, 8 * (pfn / 64)) == 8, + "Set page_idle bits for PFN 0x%" PRIx64, pfn); +} + +static void mark_vcpu_memory_idle(struct kvm_vm *vm, int vcpu_id) +{ + uint64_t base_gva = perf_test_args.vcpu_args[vcpu_id].gva; + uint64_t pages = perf_test_args.vcpu_args[vcpu_id].pages; + uint64_t page; + uint64_t still_idle = 0; + uint64_t no_pfn = 0; + int page_idle_fd; + int pagemap_fd; + + /* If vCPUs are using an overlapping region, let vCPU 0 mark it idle. */ + if (overlap_memory_access && vcpu_id) + return; + + page_idle_fd = open("/sys/kernel/mm/page_idle/bitmap", O_RDWR); + TEST_ASSERT(page_idle_fd > 0, "Failed to open page_idle."); + + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); + TEST_ASSERT(pagemap_fd > 0, "Failed to open pagemap."); + + for (page = 0; page < pages; page++) { + uint64_t gva = base_gva + page * perf_test_args.guest_page_size; + uint64_t pfn = lookup_pfn(pagemap_fd, vm, gva); + + if (!pfn) { + no_pfn++; + continue; + } + + if (is_page_idle(page_idle_fd, pfn)) { + still_idle++; + continue; + } + + mark_page_idle(page_idle_fd, pfn); + } + + /* + * Assumption: Less than 1% of pages are going to be swapped out from + * under us during this test. + */ + TEST_ASSERT(no_pfn < pages / 100, + "vCPU %d: No PFN for %" PRIu64 " out of %" PRIu64 " pages.", + vcpu_id, no_pfn, pages); + + /* + * Test that at least 90% of memory has been marked idle (the rest might + * not be marked idle because the pages have not yet made it to an LRU + * list or the translations are still cached in the TLB). 90% is + * 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. + */ + TEST_ASSERT(still_idle < pages / 10, + "vCPU%d: Too many pages still idle (%"PRIu64 " out of %" + PRIu64 ").\n", + vcpu_id, still_idle, pages); + + close(page_idle_fd); + close(pagemap_fd); +} + +static void assert_ucall(struct kvm_vm *vm, uint32_t vcpu_id, + uint64_t expected_ucall) +{ + struct ucall uc; + uint64_t actual_ucall = get_ucall(vm, vcpu_id, &uc); + + TEST_ASSERT(expected_ucall == actual_ucall, + "Guest exited unexpectedly (expected ucall %" PRIu64 + ", got %" PRIu64 ")", + expected_ucall, actual_ucall); +} + +static bool spin_wait_for_next_iteration(int *current_iteration) +{ + int last_iteration = *current_iteration; + + do { + if (READ_ONCE(done)) + return false; + + *current_iteration = READ_ONCE(iteration); + } while (last_iteration == *current_iteration); + + return true; +} + +static void *vcpu_thread_main(void *arg) +{ + struct perf_test_vcpu_args *vcpu_args = arg; + struct kvm_vm *vm = perf_test_args.vm; + int vcpu_id = vcpu_args->vcpu_id; + int current_iteration = -1; + + vcpu_args_set(vm, vcpu_id, 1, vcpu_id); + + while (spin_wait_for_next_iteration(¤t_iteration)) { + switch (READ_ONCE(iteration_work)) { + case ITERATION_ACCESS_MEMORY: + vcpu_run(vm, vcpu_id); + assert_ucall(vm, vcpu_id, UCALL_SYNC); + break; + case ITERATION_MARK_IDLE: + mark_vcpu_memory_idle(vm, vcpu_id); + break; + }; + + vcpu_last_completed_iteration[vcpu_id] = current_iteration; + } + + return NULL; +} + +static void spin_wait_for_vcpu(int vcpu_id, int target_iteration) +{ + while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != + target_iteration) { + continue; + } +} + +/* The type of memory accesses to perform in the VM. */ +enum access_type { + ACCESS_READ, + ACCESS_WRITE, +}; + +static void run_iteration(struct kvm_vm *vm, int vcpus, const char *description) +{ + struct timespec ts_start; + struct timespec ts_elapsed; + int next_iteration; + int vcpu_id; + + /* Kick off the vCPUs by incrementing iteration. */ + next_iteration = ++iteration; + + clock_gettime(CLOCK_MONOTONIC, &ts_start); + + /* Wait for all vCPUs to finish the iteration. */ + for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) + spin_wait_for_vcpu(vcpu_id, next_iteration); + + ts_elapsed = timespec_elapsed(ts_start); + pr_info("%-30s: %ld.%09lds\n", + description, ts_elapsed.tv_sec, ts_elapsed.tv_nsec); +} + +static void access_memory(struct kvm_vm *vm, int vcpus, enum access_type access, + const char *description) +{ + perf_test_args.wr_fract = (access == ACCESS_READ) ? INT_MAX : 1; + sync_global_to_guest(vm, perf_test_args); + iteration_work = ITERATION_ACCESS_MEMORY; + run_iteration(vm, vcpus, description); +} + +static void mark_memory_idle(struct kvm_vm *vm, int vcpus) +{ + /* + * 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 + * lock. + */ + pr_debug("Marking VM memory idle (slow)...\n"); + iteration_work = ITERATION_MARK_IDLE; + run_iteration(vm, vcpus, "Mark memory idle"); +} + +static pthread_t *create_vcpu_threads(int vcpus) +{ + pthread_t *vcpu_threads; + int i; + + vcpu_threads = malloc(vcpus * sizeof(vcpu_threads[0])); + TEST_ASSERT(vcpu_threads, "Failed to allocate vcpu_threads."); + + for (i = 0; i < vcpus; i++) { + vcpu_last_completed_iteration[i] = iteration; + pthread_create(&vcpu_threads[i], NULL, vcpu_thread_main, + &perf_test_args.vcpu_args[i]); + } + + return vcpu_threads; +} + +static void terminate_vcpu_threads(pthread_t *vcpu_threads, int vcpus) +{ + int i; + + /* Set done to signal the vCPU threads to exit */ + done = true; + + for (i = 0; i < vcpus; i++) + pthread_join(vcpu_threads[i], NULL); +} + +static void run_test(enum vm_guest_mode mode, void *arg) +{ + struct test_params *params = arg; + struct kvm_vm *vm; + pthread_t *vcpu_threads; + int vcpus = params->vcpus; + + vm = perf_test_create_vm(mode, vcpus, params->vcpu_memory_bytes, + params->backing_src); + + perf_test_setup_vcpus(vm, vcpus, params->vcpu_memory_bytes, + !overlap_memory_access); + + vcpu_threads = create_vcpu_threads(vcpus); + + pr_info("\n"); + access_memory(vm, vcpus, ACCESS_WRITE, "Populating memory"); + + /* As a control, read and write to the populated memory first. */ + access_memory(vm, vcpus, ACCESS_WRITE, "Writing to populated memory"); + access_memory(vm, vcpus, ACCESS_READ, "Reading from populated memory"); + + /* Repeat on memory that has been marked as idle. */ + mark_memory_idle(vm, vcpus); + access_memory(vm, vcpus, ACCESS_WRITE, "Writing to idle memory"); + mark_memory_idle(vm, vcpus); + access_memory(vm, vcpus, ACCESS_READ, "Reading from idle memory"); + + terminate_vcpu_threads(vcpu_threads, vcpus); + free(vcpu_threads); + perf_test_destroy_vm(vm); +} + +static void help(char *name) +{ + puts(""); + printf("usage: %s [-h] [-m mode] [-b vcpu_bytes] [-v vcpus] [-o] [-s mem_type]\n", + name); + puts(""); + printf(" -h: Display this help message."); + guest_modes_help(); + printf(" -b: specify the size of the memory region which should be\n" + " dirtied by each vCPU. e.g. 10M or 3G.\n" + " (default: 1G)\n"); + 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(" -s: specify the type of memory that should be used to\n" + " back the guest data region.\n\n"); + backing_src_help(); + puts(""); + exit(0); +} + +int main(int argc, char *argv[]) +{ + struct test_params params = { + .backing_src = VM_MEM_SRC_ANONYMOUS, + .vcpu_memory_bytes = DEFAULT_PER_VCPU_MEM_SIZE, + .vcpus = 1, + }; + int page_idle_fd; + int opt; + + guest_modes_append_default(); + + while ((opt = getopt(argc, argv, "hm:b:v:os:")) != -1) { + switch (opt) { + case 'm': + guest_modes_cmdline(optarg); + break; + case 'b': + params.vcpu_memory_bytes = parse_size(optarg); + break; + case 'v': + params.vcpus = atoi(optarg); + break; + case 'o': + overlap_memory_access = true; + break; + case 's': + params.backing_src = parse_backing_src_type(optarg); + break; + case 'h': + default: + help(argv[0]); + break; + } + } + + page_idle_fd = open("/sys/kernel/mm/page_idle/bitmap", O_RDWR); + if (page_idle_fd < 0) { + print_skip("CONFIG_IDLE_PAGE_TRACKING is not enabled"); + exit(KSFT_SKIP); + } + close(page_idle_fd); + + for_each_guest_mode(run_test, ¶ms); + + return 0; +}