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KVM: selftests: Add configurable demand paging delay

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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@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ben Gardon 2020-02-20 18:09:59 +01:00 committed by Paolo Bonzini
parent 4f72180eb4
commit 0119cb365c
1 changed files with 25 additions and 7 deletions
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32
tools/testing/selftests/kvm/demand_paging_test.c
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@ -145,6 +145,7 @@ bool quit_uffd_thread;
struct uffd_handler_args {
int uffd;
int pipefd;
useconds_t delay;
};
static void *uffd_handler_thread_fn(void *arg)
@ -152,6 +153,7 @@ 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) {
@ -212,6 +214,8 @@ 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)
@ -223,7 +227,8 @@ 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;
@ -264,6 +269,7 @@ 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);
@ -273,7 +279,8 @@ 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;
@ -341,7 +348,8 @@ 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),
guest_modes[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 __x86_64__
guest_mode_init(VM_MODE_PXXV48_4K, true, true);
@ -437,7 +450,7 @@ int main(int argc, char *argv[])
guest_mode_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) {
@ -453,6 +466,11 @@ 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]);
@ -466,7 +484,7 @@ int main(int argc, char *argv[])
TEST_ASSERT(guest_modes[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;