Provide a generic function to read the system counter from the guest for timing purposes. An increasingly common and important way to measure guest performance is to measure the amount of time different actions take in the guest. Provide also a mathematical conversion from cycles to nanoseconds and a macro for timing individual statements. Substitute the previous custom implementation of a similar function in system_counter_offset_test with this new implementation. Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx> --- These functions were originally part of my patch to introduce latency measurements into dirty_log_perf_test. [1] Sean Christopherson suggested lifting these functions into their own patch in generic code so they can be used by any test. [2] Ricardo Koller suggested the addition of the MEASURE macro to more easily time individual statements. [3] [1] https://lore.kernel.org/kvm/20221115173258.2530923-1-coltonlewis@xxxxxxxxxx/ [2] https://lore.kernel.org/kvm/Y8gfOP5CMXK60AtH@xxxxxxxxxx/ [3] https://lore.kernel.org/kvm/Y8cIdxp5k8HivVAe@xxxxxxxxxx/ .../testing/selftests/kvm/include/test_util.h | 3 ++ tools/testing/selftests/kvm/lib/test_util.c | 37 +++++++++++++++++++ .../kvm/system_counter_offset_test.c | 10 +---- 3 files changed, 42 insertions(+), 8 deletions(-) diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h index 80d6416f3012..290653b99035 100644 --- a/tools/testing/selftests/kvm/include/test_util.h +++ b/tools/testing/selftests/kvm/include/test_util.h @@ -84,6 +84,9 @@ struct guest_random_state { struct guest_random_state new_guest_random_state(uint32_t seed); uint32_t guest_random_u32(struct guest_random_state *state); +uint64_t guest_cycles_read(void); +double guest_cycles_to_ns(double cycles); + enum vm_mem_backing_src_type { VM_MEM_SRC_ANONYMOUS, VM_MEM_SRC_ANONYMOUS_THP, diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c index 5c22fa4c2825..6d88132a0131 100644 --- a/tools/testing/selftests/kvm/lib/test_util.c +++ b/tools/testing/selftests/kvm/lib/test_util.c @@ -15,6 +15,11 @@ #include <linux/mman.h> #include "linux/kernel.h" +#if defined(__aarch64__) +#include "aarch64/arch_timer.h" +#elif defined(__x86_64__) +#include "x86_64/processor.h" +#endif #include "test_util.h" /* @@ -34,6 +39,38 @@ uint32_t guest_random_u32(struct guest_random_state *state) return state->seed; } +uint64_t guest_cycles_read(void) +{ +#if defined(__aarch64__) + return timer_get_cntct(VIRTUAL); +#elif defined(__x86_64__) + return rdtsc(); +#else +#warn __func__ " is not implemented for this architecture, will return 0" + return 0; +#endif +} + +double guest_cycles_to_ns(double cycles) +{ +#if defined(__aarch64__) + return cycles * (1e9 / timer_get_cntfrq()); +#elif defined(__x86_64__) + return cycles * (1e9 / (KVM_GET_TSC_KHZ * 1000)); +#else +#warn __func__ " is not implemented for this architecture, will return 0" + return 0.0; +#endif +} + +#define MEASURE_CYCLES(x) \ + ({ \ + uint64_t start; \ + start = guest_cycles_read(); \ + x; \ + guest_cycles_read() - start; \ + }) + /* * Parses "[0-9]+[kmgt]?". */ diff --git a/tools/testing/selftests/kvm/system_counter_offset_test.c b/tools/testing/selftests/kvm/system_counter_offset_test.c index 7f5b330b6a1b..39b1249c7404 100644 --- a/tools/testing/selftests/kvm/system_counter_offset_test.c +++ b/tools/testing/selftests/kvm/system_counter_offset_test.c @@ -39,14 +39,9 @@ static void setup_system_counter(struct kvm_vcpu *vcpu, struct test_case *test) &test->tsc_offset); } -static uint64_t guest_read_system_counter(struct test_case *test) -{ - return rdtsc(); -} - static uint64_t host_read_guest_system_counter(struct test_case *test) { - return rdtsc() + test->tsc_offset; + return guest_cycles_read() + test->tsc_offset; } #else /* __x86_64__ */ @@ -63,9 +58,8 @@ static void guest_main(void) int i; for (i = 0; i < ARRAY_SIZE(test_cases); i++) { - struct test_case *test = &test_cases[i]; - GUEST_SYNC_CLOCK(i, guest_read_system_counter(test)); + GUEST_SYNC_CLOCK(i, guest_cycles_read()); } } -- 2.39.2.637.g21b0678d19-goog
