[PATCH v2 6/8] KVM: selftests: Support multiple vCPUs in demand paging test

Ben Gardon
2019-12-16T21:36:25Z

Most VMs have multiple vCPUs, the concurrent execution of which has a
substantial impact on demand paging performance. Add an option to create
multiple vCPUs to each access disjoint regions of memory.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
.../selftests/kvm/demand_paging_test.c | 199 ++++++++++++------
1 file changed, 136 insertions(+), 63 deletions(-)

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index 8ede26e088ab6..2b80f614dd537 100644
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -24,8 +24,6 @@
#include "kvm_util.h"
#include "processor.h"

-#define VCPU_ID 1
-
/* The memory slot index demand page */
#define TEST_MEM_SLOT_INDEX 1

@@ -34,6 +32,12 @@

#define DEFAULT_GUEST_TEST_MEM_SIZE (1 << 30) /* 1G */

+#ifdef PRINT_PER_VCPU_UPDATES
+#define PER_VCPU_DEBUG(...) DEBUG(__VA_ARGS__)
+#else
+#define PER_VCPU_DEBUG(...)
+#endif
+
/*
* Guest/Host shared variables. Ensure addr_gva2hva() and/or
* sync_global_to/from_guest() are used when accessing from
@@ -76,10 +80,6 @@ static void guest_code(uint64_t gva, uint64_t pages)
GUEST_SYNC(1);
}

-/* Points to the test VM memory region on which we are doing demand paging */
-static void *host_test_mem;
-static uint64_t host_num_pages;
-
struct vcpu_thread_args {
uint64_t gva;
uint64_t pages;
@@ -113,18 +113,32 @@ static void *vcpu_worker(void *data)
return NULL;
}

-static struct kvm_vm *create_vm(enum vm_guest_mode mode, uint32_t vcpuid,
- uint64_t extra_mem_pages, void *guest_code)
+#define PAGE_SHIFT_4K 12
+#define PTES_PER_PT 512
+
+static struct kvm_vm *create_vm(enum vm_guest_mode mode, int vcpus,
+ uint64_t vcpu_wss)
{
struct kvm_vm *vm;
- uint64_t extra_pg_pages = extra_mem_pages / 512 * 2;
+ uint64_t pages = DEFAULT_GUEST_PHY_PAGES;

- vm = _vm_create(mode, DEFAULT_GUEST_PHY_PAGES + extra_pg_pages, O_RDWR);
+ /* Account for a few pages per-vCPU for stacks */
+ pages += DEFAULT_STACK_PGS * vcpus;
+
+ /*
+ * Reserve twice the ammount of memory needed to map the test region and
+ * the page table / stacks region, at 4k, for page tables. Do the
+ * calculation with 4K page size: the smallest of all archs. (e.g., 64K
+ * page size guest will need even less memory for page tables).
+ */
+ pages += (2 * pages) / PTES_PER_PT;
+ pages += ((2 * vcpus * vcpu_wss) >> PAGE_SHIFT_4K) / PTES_PER_PT;
+
+ vm = _vm_create(mode, pages, O_RDWR);
kvm_vm_elf_load(vm, program_invocation_name, 0, 0);
#ifdef __x86_64__
vm_create_irqchip(vm);
#endif
- vm_vcpu_add_default(vm, vcpuid, guest_code);
return vm;
}

@@ -232,15 +246,13 @@ static void *uffd_handler_thread_fn(void *arg)

static int setup_demand_paging(struct kvm_vm *vm,
pthread_t *uffd_handler_thread,
- useconds_t uffd_delay)
+ useconds_t uffd_delay,
+ struct uffd_handler_args *uffd_args,
+ void *hva, uint64_t len)
{
int uffd;
struct uffdio_api uffdio_api;
struct uffdio_register uffdio_register;
- struct uffd_handler_args uffd_args;
-
- guest_data_prototype = malloc(host_page_size);
- memset(guest_data_prototype, 0xAB, host_page_size);

uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
if (uffd == -1) {
@@ -255,8 +267,8 @@ static int setup_demand_paging(struct kvm_vm *vm,
return -1;
}

- uffdio_register.range.start = (uint64_t)host_test_mem;
- uffdio_register.range.len = host_num_pages * host_page_size;
+ uffdio_register.range.start = (uint64_t)hva;
+ uffdio_register.range.len = len;
uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) == -1) {
DEBUG("ioctl uffdio_register failed\n");
@@ -269,42 +281,37 @@ static int setup_demand_paging(struct kvm_vm *vm,
return -1;
}

- uffd_args.uffd = uffd;
- uffd_args.delay = uffd_delay;
+ uffd_args->uffd = uffd;
+ uffd_args->delay = uffd_delay;
pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn,
- &uffd_args);
+ uffd_args);
+
+ PER_VCPU_DEBUG("Created uffd thread for HVA range [%p, %p)\n",
+ hva, hva + len);

return 0;
}

-#define PAGE_SHIFT_4K 12
-
static void run_test(enum vm_guest_mode mode, bool use_uffd,
- useconds_t uffd_delay, uint64_t vcpu_wss)
+ useconds_t uffd_delay, int vcpus, uint64_t vcpu_wss)
{
- pthread_t vcpu_thread;
- pthread_t uffd_handler_thread;
+ pthread_t *vcpu_threads;
+ pthread_t *uffd_handler_threads = NULL;
+ struct uffd_handler_args *uffd_args = NULL;
struct kvm_vm *vm;
- struct vcpu_thread_args vcpu_args;
+ struct vcpu_thread_args *vcpu_args;
uint64_t guest_num_pages;
+ int vcpu_id;
int r;

- /*
- * We reserve page table for twice the ammount of memory we intend
- * to use in the test region for demand paging. Here we do the
- * calculation with 4K page size which is the smallest so the page
- * number will be enough for all archs. (e.g., 64K page size guest
- * will need even less memory for page tables).
- */
- vm = create_vm(mode, VCPU_ID, (2 * vcpu_wss) >> PAGE_SHIFT_4K,
- guest_code);
+ vm = create_vm(mode, vcpus, vcpu_wss);

guest_page_size = vm_get_page_size(vm);

TEST_ASSERT(vcpu_wss % guest_page_size == 0,
"Guest memory size is not guest page size aligned.");

- guest_num_pages = vcpu_wss / guest_page_size;
+ guest_num_pages = (vcpus * vcpu_wss) / guest_page_size;

#ifdef __s390x__
/* Round up to multiple of 1M (segment size) */
@@ -316,13 +323,12 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
*/
TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),
"Requested more guest memory than address space allows.\n"
- " guest pages: %lx max gfn: %lx\n",
- guest_num_pages, vm_get_max_gfn(vm));
+ " guest pages: %lx max gfn: %lx vcpus: %d wss: %lx]\n",
+ guest_num_pages, vm_get_max_gfn(vm), vcpus, vcpu_wss);

host_page_size = getpagesize();
TEST_ASSERT(vcpu_wss % host_page_size == 0,
"Guest memory size is not host page size aligned.");
- host_num_pages = vcpu_wss / host_page_size;

guest_test_phys_mem = (vm_get_max_gfn(vm) - guest_num_pages) *
guest_page_size;
@@ -347,43 +353,102 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
virt_map(vm, guest_test_virt_mem, guest_test_phys_mem,
guest_num_pages * guest_page_size, 0);

- /* Cache the HVA pointer of the region */
- host_test_mem = addr_gpa2hva(vm, (vm_paddr_t)guest_test_phys_mem);
+ /* Export the shared variables to the guest */
+ sync_global_to_guest(vm, host_page_size);
+ sync_global_to_guest(vm, guest_page_size);
+
+ guest_data_prototype = malloc(host_page_size);
+ TEST_ASSERT(guest_data_prototype, "Memory allocation failed");
+ memset(guest_data_prototype, 0xAB, host_page_size);
+
+ vcpu_threads = malloc(vcpus * sizeof(*vcpu_threads));
+ TEST_ASSERT(vcpu_threads, "Memory allocation failed");

if (use_uffd) {
- /* Set up user fault fd to handle demand paging requests. */
quit_uffd_thread = false;
- r = setup_demand_paging(vm, &uffd_handler_thread,
- uffd_delay);
- if (r < 0)
- exit(-r);
+
+ uffd_handler_threads =
+ malloc(vcpus * sizeof(*uffd_handler_threads));
+ TEST_ASSERT(uffd_handler_threads, "Memory allocation failed");
+
+ uffd_args = malloc(vcpus * sizeof(*uffd_args));
+ TEST_ASSERT(uffd_args, "Memory allocation failed");
}

+ vcpu_args = malloc(vcpus * sizeof(*vcpu_args));
+ TEST_ASSERT(vcpu_args, "Memory allocation failed");
+
+ for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+ vm_paddr_t vcpu_gpa;
+ void *vcpu_hva;
+
+ vm_vcpu_add_default(vm, vcpu_id, guest_code);
+
+ vcpu_gpa = guest_test_phys_mem + (vcpu_id * vcpu_wss);
+ PER_VCPU_DEBUG("Added VCPU %d with test mem gpa [%lx, %lx)\n",
+ vcpu_id, vcpu_gpa, vcpu_gpa + vcpu_wss);
+
+ /* Cache the HVA pointer of the region */
+ vcpu_hva = addr_gpa2hva(vm, vcpu_gpa);
+
+ if (use_uffd) {
+ /*
+ * Set up user fault fd to handle demand paging
+ * requests.
+ */
+ r = setup_demand_paging(vm,
+ &uffd_handler_threads[vcpu_id],
+ uffd_delay, &uffd_args[vcpu_id],
+ vcpu_hva, vcpu_wss);
+ if (r < 0)
+ exit(-r);
+ }
+
#ifdef __x86_64__
- vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
+ vcpu_set_cpuid(vm, vcpu_id, kvm_get_supported_cpuid());
#endif

- /* Export the shared variables to the guest */
- sync_global_to_guest(vm, host_page_size);
- sync_global_to_guest(vm, guest_page_size);
+ vcpu_args[vcpu_id].vm = vm;
+ vcpu_args[vcpu_id].vcpu_id = vcpu_id;
+ vcpu_args[vcpu_id].gva = guest_test_virt_mem +
+ (vcpu_id * vcpu_wss);
+ vcpu_args[vcpu_id].pages = vcpu_wss / guest_page_size;
+ }
+
+ DEBUG("Finished creating vCPUs and starting uffd threads\n");
+
+ for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+ pthread_create(&vcpu_threads[vcpu_id], NULL, vcpu_worker,
+ &vcpu_args[vcpu_id]);
+ }
+
+ DEBUG("Started all vCPUs\n");

- vcpu_args.vm = vm;
- vcpu_args.vcpu_id = VCPU_ID;
- vcpu_args.gva = guest_test_virt_mem;
- vcpu_args.pages = guest_num_pages;
- pthread_create(&vcpu_thread, NULL, vcpu_worker, &vcpu_args);
+ /* Wait for the vcpu threads to quit */
+ for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++) {
+ pthread_join(vcpu_threads[vcpu_id], NULL);
+ PER_VCPU_DEBUG("Joined thread for vCPU %d\n", vcpu_id);
+ }

- /* Wait for the vcpu thread to quit */
- pthread_join(vcpu_thread, NULL);
+ DEBUG("All vCPU threads joined\n");

if (use_uffd) {
- /* Tell the user fault fd handler thread to quit */
+ /* Tell the user fault fd handler threads to quit */
quit_uffd_thread = true;
- pthread_join(uffd_handler_thread, NULL);
+ for (vcpu_id = 0; vcpu_id < vcpus; vcpu_id++)
+ pthread_join(uffd_handler_threads[vcpu_id], NULL);
}

ucall_uninit(vm);
kvm_vm_free(vm);
+
+ free(guest_data_prototype);
+ free(vcpu_threads);
+ if (use_uffd) {
+ free(uffd_handler_threads);
+ free(uffd_args);
+ }
+ free(vcpu_args);
}

struct vm_guest_mode_params {
@@ -404,7 +469,7 @@ static void help(char *name)

puts("");
printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n"
- " [-b bytes test memory]\n", name);
+ " [-b bytes test memory] [-v vcpus]\n", name);
printf(" -m: specify the guest mode ID to test\n"
" (default: test all supported modes)\n"
" This option may be used multiple times.\n"
@@ -419,6 +484,7 @@ static void help(char *name)
" FD handler to simulate demand paging\n"
" overheads. Ignored without -u.\n");
printf(" -b: specify the working set size, in bytes for each vCPU.\n");
+ printf(" -v: specify the number of vCPUs to run.\n");
puts("");
exit(0);
}
@@ -427,6 +493,7 @@ int main(int argc, char *argv[])
{
bool mode_selected = false;
uint64_t vcpu_wss = DEFAULT_GUEST_TEST_MEM_SIZE;
+ int vcpus = 1;
unsigned int mode;
int opt, i;
bool use_uffd = false;
@@ -439,7 +506,7 @@ int main(int argc, char *argv[])
vm_guest_mode_params_init(VM_MODE_P40V48_4K, true, true);
#endif

- while ((opt = getopt(argc, argv, "hm:ud:b:")) != -1) {
+ while ((opt = getopt(argc, argv, "hm:ud:b:v:")) != -1) {
switch (opt) {
case 'm':
if (!mode_selected) {
@@ -462,6 +529,12 @@ int main(int argc, char *argv[])
break;
case 'b':
vcpu_wss = strtoull(optarg, NULL, 0);
+ break;
+ case 'v':
+ vcpus = atoi(optarg);
+ TEST_ASSERT(vcpus > 0,
+ "Must have a positive number of vCPUs");
+ break;
case 'h':
default:
help(argv[0]);
@@ -475,7 +548,7 @@ int main(int argc, char *argv[])
TEST_ASSERT(vm_guest_mode_params[i].supported,
"Guest mode ID %d (%s) not supported.",
i, vm_guest_mode_string(i));
- run_test(i, use_uffd, uffd_delay, vcpu_wss);
+ run_test(i, use_uffd, uffd_delay, vcpus, vcpu_wss);
}

return 0;
--
2.24.1.735.g03f4e72817-goog