[PATCH 3/5] KVM: selftests: Simplify demand_paging_test with timespec_diff_now

Ben Gardon
2020-10-28T01:48:27Z

Add a helper function to get the current time and return the time since
a given start time. Use that function to simplify the timekeeping in the
demand paging test.

This series was tested by running the following invocations on an Intel
Skylake machine:
dirty_log_perf_test -b 20m -i 100 -v 64
dirty_log_perf_test -b 20g -i 5 -v 4
dirty_log_perf_test -b 4g -i 5 -v 32
demand_paging_test -b 20m -v 64
demand_paging_test -b 20g -v 4
demand_paging_test -b 4g -v 32
All behaved as expected.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
.../selftests/kvm/demand_paging_test.c | 26 +++++++++----------
.../testing/selftests/kvm/include/test_util.h | 1 +
tools/testing/selftests/kvm/lib/test_util.c | 15 +++++++++--
3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index 4251e98ceb69f..7de6feb000760 100644
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -50,7 +50,8 @@ static void *vcpu_worker(void *data)
int vcpu_id = vcpu_args->vcpu_id;
struct kvm_vm *vm = perf_test_args.vm;
struct kvm_run *run;
- struct timespec start, end, ts_diff;
+ struct timespec start;
+ struct timespec ts_diff;

vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
run = vcpu_state(vm, vcpu_id);
@@ -66,8 +67,7 @@ static void *vcpu_worker(void *data)
exit_reason_str(run->exit_reason));
}

- clock_gettime(CLOCK_MONOTONIC, &end);
- ts_diff = timespec_sub(end, start);
+ ts_diff = timespec_diff_now(start);
PER_VCPU_DEBUG("vCPU %d execution time: %ld.%.9lds\n", vcpu_id,
ts_diff.tv_sec, ts_diff.tv_nsec);

@@ -78,7 +78,7 @@ static int handle_uffd_page_request(int uffd, uint64_t addr)
{
pid_t tid;
struct timespec start;
- struct timespec end;
+ struct timespec ts_diff;
struct uffdio_copy copy;
int r;

@@ -98,10 +98,10 @@ static int handle_uffd_page_request(int uffd, uint64_t addr)
return r;
}

- clock_gettime(CLOCK_MONOTONIC, &end);
+ ts_diff = timespec_diff_now(start);

PER_PAGE_DEBUG("UFFDIO_COPY %d \t%ld ns\n", tid,
- timespec_to_ns(timespec_sub(end, start)));
+ timespec_to_ns(ts_diff));
PER_PAGE_DEBUG("Paged in %ld bytes at 0x%lx from thread %d\n",
perf_test_args.host_page_size, addr, tid);

@@ -123,7 +123,8 @@ static void *uffd_handler_thread_fn(void *arg)
int pipefd = uffd_args->pipefd;
useconds_t delay = uffd_args->delay;
int64_t pages = 0;
- struct timespec start, end, ts_diff;
+ struct timespec start;
+ struct timespec ts_diff;

clock_gettime(CLOCK_MONOTONIC, &start);
while (!quit_uffd_thread) {
@@ -192,8 +193,7 @@ static void *uffd_handler_thread_fn(void *arg)
pages++;
}

- clock_gettime(CLOCK_MONOTONIC, &end);
- ts_diff = timespec_sub(end, start);
+ ts_diff = timespec_diff_now(start);
PER_VCPU_DEBUG("userfaulted %ld pages over %ld.%.9lds. (%f/sec)\n",
pages, ts_diff.tv_sec, ts_diff.tv_nsec,
pages / ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / 100000000.0));
@@ -257,7 +257,8 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
pthread_t *vcpu_threads;
pthread_t *uffd_handler_threads = NULL;
struct uffd_handler_args *uffd_args = NULL;
- struct timespec start, end, ts_diff;
+ struct timespec start;
+ struct timespec ts_diff;
int *pipefds = NULL;
struct kvm_vm *vm;
int vcpu_id;
@@ -335,9 +336,9 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
PER_VCPU_DEBUG("Joined thread for vCPU %d\n", vcpu_id);
}

- pr_info("All vCPU threads joined\n");
+ ts_diff = timespec_diff_now(start);

- clock_gettime(CLOCK_MONOTONIC, &end);
+ pr_info("All vCPU threads joined\n");

if (use_uffd) {
char c;
@@ -351,7 +352,6 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
}
}

- ts_diff = timespec_sub(end, start);
pr_info("Total guest execution time: %ld.%.9lds\n",
ts_diff.tv_sec, ts_diff.tv_nsec);
pr_info("Overall demand paging rate: %f pgs/sec\n",
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index 5eb01bf51b86f..1cc036ddb0c5e 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -64,5 +64,6 @@ int64_t timespec_to_ns(struct timespec ts);
struct timespec timespec_add_ns(struct timespec ts, int64_t ns);
struct timespec timespec_add(struct timespec ts1, struct timespec ts2);
struct timespec timespec_sub(struct timespec ts1, struct timespec ts2);
+struct timespec timespec_diff_now(struct timespec start);

#endif /* SELFTEST_KVM_TEST_UTIL_H */
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 689e97c27ee24..1a46c2c48c7cb 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -4,10 +4,13 @@
*
* Copyright (C) 2020, Google LLC.
*/
-#include <stdlib.h>
+
+#include <assert.h>
#include <ctype.h>
#include <limits.h>
-#include <assert.h>
+#include <stdlib.h>
+#include <time.h>
+
#include "test_util.h"

/*
@@ -81,6 +84,14 @@ struct timespec timespec_sub(struct timespec ts1, struct timespec ts2)
return timespec_add_ns((struct timespec){0}, ns1 - ns2);
}

+struct timespec timespec_diff_now(struct timespec start)
+{
+ struct timespec end;
+
+ clock_gettime(CLOCK_MONOTONIC, &end);
+ return timespec_sub(end, start);
+}
+
void print_skip(const char *fmt, ...)
{
va_list ap;
--
2.29.0.rc2.309.g374f81d7ae-goog