When running the demand paging test with the -u option, the User Fault FD handler essentially adds an arbitrary delay to page fault resolution. To enable better simulation of a real demand paging scenario, add a configurable delay to the UFFD handler.
Signed-off-by: Ben Gardon bgardon@google.com --- .../selftests/kvm/demand_paging_test.c | 32 +++++++++++++++---- 1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c index a8f775dab7d4a..11de5b58995fb 100644 --- a/tools/testing/selftests/kvm/demand_paging_test.c +++ b/tools/testing/selftests/kvm/demand_paging_test.c @@ -142,12 +142,14 @@ bool quit_uffd_thread;
struct uffd_handler_args { int uffd; + useconds_t delay; };
static void *uffd_handler_thread_fn(void *arg) { struct uffd_handler_args *uffd_args = (struct uffd_handler_args *)arg; int uffd = uffd_args->uffd; + useconds_t delay = uffd_args->delay; int64_t pages = 0;
while (!quit_uffd_thread) { @@ -203,6 +205,8 @@ static void *uffd_handler_thread_fn(void *arg) if (!(msg.event & UFFD_EVENT_PAGEFAULT)) continue;
+ if (delay) + usleep(delay); addr = msg.arg.pagefault.address; r = handle_uffd_page_request(uffd, addr); if (r < 0) @@ -214,7 +218,8 @@ static void *uffd_handler_thread_fn(void *arg) }
static int setup_demand_paging(struct kvm_vm *vm, - pthread_t *uffd_handler_thread) + pthread_t *uffd_handler_thread, + useconds_t uffd_delay) { int uffd; struct uffdio_api uffdio_api; @@ -252,6 +257,7 @@ static int setup_demand_paging(struct kvm_vm *vm, }
uffd_args.uffd = uffd; + uffd_args.delay = uffd_delay; pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn, &uffd_args);
@@ -261,7 +267,8 @@ static int setup_demand_paging(struct kvm_vm *vm, #define GUEST_MEM_SHIFT 30 /* 1G */ #define PAGE_SHIFT_4K 12
-static void run_test(enum vm_guest_mode mode, bool use_uffd) +static void run_test(enum vm_guest_mode mode, bool use_uffd, + useconds_t uffd_delay) { pthread_t vcpu_thread; pthread_t uffd_handler_thread; @@ -326,7 +333,8 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd) 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); + r = setup_demand_paging(vm, &uffd_handler_thread, + uffd_delay); if (r < 0) exit(-r); } @@ -373,7 +381,7 @@ static void help(char *name) int i;
puts(""); - printf("usage: %s [-h] [-m mode] [-u]\n", name); + printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\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" @@ -382,7 +390,11 @@ static void help(char *name) printf(" %d: %s%s\n", i, vm_guest_mode_string(i), vm_guest_mode_params[i].supported ? " (supported)" : ""); } - printf(" -u: Use User Fault FD to handle vCPU page faults.\n"); + printf(" -u: use User Fault FD to handle vCPU page\n" + " faults.\n"); + printf(" -d: add a delay in usec to the User Fault\n" + " FD handler to simulate demand paging\n" + " overheads. Ignored without -u.\n"); puts(""); exit(0); } @@ -393,6 +405,7 @@ int main(int argc, char *argv[]) unsigned int mode; int opt, i; bool use_uffd = false; + useconds_t uffd_delay = 0;
#ifdef __x86_64__ vm_guest_mode_params_init(VM_MODE_PXXV48_4K, true, true); @@ -401,7 +414,7 @@ int main(int argc, char *argv[]) vm_guest_mode_params_init(VM_MODE_P40V48_4K, true, true); #endif
- while ((opt = getopt(argc, argv, "hm:u")) != -1) { + while ((opt = getopt(argc, argv, "hm:ud:")) != -1) { switch (opt) { case 'm': if (!mode_selected) { @@ -417,6 +430,11 @@ int main(int argc, char *argv[]) case 'u': use_uffd = true; break; + case 'd': + uffd_delay = strtoul(optarg, NULL, 0); + TEST_ASSERT(uffd_delay >= 0, + "A negative UFFD delay is not supported."); + break; case 'h': default: help(argv[0]); @@ -430,7 +448,7 @@ 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); + run_test(i, use_uffd, uffd_delay); }
return 0;