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.
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
.../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 6fab4468f97f6..01d2c76ada55d 100644
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -143,6 +143,7 @@ bool quit_uffd_thread;
struct uffd_handler_args {
int uffd;
int pipefd;
+ useconds_t delay;
};
static void *uffd_handler_thread_fn(void *arg)
@@ -150,6 +151,7 @@ static void *uffd_handler_thread_fn(void *arg)
struct uffd_handler_args *uffd_args = (struct uffd_handler_args *)arg;
int uffd = uffd_args->uffd;
int pipefd = uffd_args->pipefd;
+ useconds_t delay = uffd_args->delay;
int64_t pages = 0;
while (!quit_uffd_thread) {
@@ -210,6 +212,8 @@ 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)
@@ -221,7 +225,8 @@ static void *uffd_handler_thread_fn(void *arg)
}
static int setup_demand_paging(struct kvm_vm *vm,
- pthread_t *uffd_handler_thread, int pipefd)
+ pthread_t *uffd_handler_thread, int pipefd,
+ useconds_t uffd_delay)
{
int uffd;
struct uffdio_api uffdio_api;
@@ -262,6 +267,7 @@ static int setup_demand_paging(struct kvm_vm *vm,
uffd_args.uffd = uffd;
uffd_args.pipefd = pipefd;
+ uffd_args.delay = uffd_delay;
pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn,
&uffd_args);
@@ -271,7 +277,8 @@ 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;
@@ -339,7 +346,8 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd)
r = pipe2(pipefd, O_CLOEXEC | O_NONBLOCK);
TEST_ASSERT(!r, "Failed to set up pipefd");
- r = setup_demand_paging(vm, &uffd_handler_thread, pipefd[0]);
+ r = setup_demand_paging(vm, &uffd_handler_thread, pipefd[0],
+ uffd_delay);
if (r < 0)
exit(-r);
}
@@ -395,7 +403,7 @@ 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"
@@ -404,7 +412,11 @@ 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);
}
@@ -415,6 +427,7 @@ int main(int argc, char *argv[])
unsigned int mode;
int opt, i;
bool use_uffd = false;
+ useconds_t uffd_delay = 0;
#ifdef __aarch64__
unsigned int host_ipa_limit;
#endif
@@ -438,7 +451,7 @@ 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) {
@@ -454,6 +467,11 @@ 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]);
@@ -467,7 +485,7 @@ 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;
--
2.25.0.341.g760bfbb309-goog
