Re: [PATCH kvm-unit-test 6/6] Add a test for kvm-clock

Glauber Costa
2010-08-27T11:34:58Z

On Fri, Aug 27, 2010 at 01:49:53PM +0800, Jason Wang wrote:
> This patch implements two tests for kvmclock. First one check whether
> the date of time returned by kvmclock matches the value got from
> host. Second one check whether the cycle of kvmclock grows
> monotonically in smp guest.
>
> Three parameters were accepted by the test: test loops, seconds
> since 1970-01-01 00:00:00 UTC which could be easily get through date
> +%s and the max accepted offset value between the tod of guest and
> host.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> config-x86-common.mak | 6 ++
> x86/README | 2 +
> x86/kvmclock_test.c | 145 +++++++++++++++++++++++++++++++++++++++++++++++++
> x86/unittests.cfg | 5 ++
> 4 files changed, 157 insertions(+), 1 deletions(-)
> create mode 100644 x86/kvmclock_test.c
>
> diff --git a/config-x86-common.mak b/config-x86-common.mak
> index b8ca859..b541c1c 100644
> --- a/config-x86-common.mak
> +++ b/config-x86-common.mak
> @@ -26,7 +26,8 @@ FLATLIBS = lib/libcflat.a $(libgcc)
> tests-common = $(TEST_DIR)/vmexit.flat $(TEST_DIR)/tsc.flat \
> $(TEST_DIR)/smptest.flat $(TEST_DIR)/port80.flat \
> $(TEST_DIR)/realmode.flat $(TEST_DIR)/msr.flat \
> - $(TEST_DIR)/hypercall.flat $(TEST_DIR)/sieve.flat
> + $(TEST_DIR)/hypercall.flat $(TEST_DIR)/sieve.flat \
> + $(TEST_DIR)/kvmclock_test.flat
>
> tests_and_config = $(TEST_DIR)/*.flat $(TEST_DIR)/unittests.cfg
>
> @@ -70,6 +71,9 @@ $(TEST_DIR)/rmap_chain.flat: $(cstart.o) $(TEST_DIR)/rmap_chain.o \
>
> $(TEST_DIR)/svm.flat: $(cstart.o) $(TEST_DIR)/vm.o
>
> +$(TEST_DIR)/kvmclock_test.flat: $(cstart.o) $(TEST_DIR)/kvmclock.o \
> + $(TEST_DIR)/kvmclock_test.o
> +
> arch_clean:
> $(RM) $(TEST_DIR)/*.o $(TEST_DIR)/*.flat \
> $(TEST_DIR)/.*.d $(TEST_DIR)/lib/.*.d $(TEST_DIR)/lib/*.o
> diff --git a/x86/README b/x86/README
> index ab5a2ae..4b90080 100644
> --- a/x86/README
> +++ b/x86/README
> @@ -12,3 +12,5 @@ sieve: heavy memory access with no paging and with paging static and with paging
> smptest: run smp_id() on every cpu and compares return value to number
> tsc: write to tsc(0) and write to tsc(100000000000) and read it back
> vmexit: long loops for each: cpuid, vmcall, mov_from_cr8, mov_to_cr8, inl_pmtimer, ipi, ipi+halt
> +kvmclock_test: monotonic cycle test of kvmclock and a sanity test of
> +wallclock
> diff --git a/x86/kvmclock_test.c b/x86/kvmclock_test.c
> new file mode 100644
> index 0000000..cd80915
> --- /dev/null
> +++ b/x86/kvmclock_test.c
> @@ -0,0 +1,145 @@
> +#include "libcflat.h"
> +#include "smp.h"
> +#include "atomic.h"
> +#include "string.h"
> +#include "kvmclock.h"
> +
> +#define DEFAULT_TEST_LOOPS 100000000L
> +#define DEFAULT_THRESHOLD 60L
> +
> + printf("Check the stability of raw cycle\n");
> + pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT
> + | PVCLOCK_RAW_CYCLE_BIT);
> + if (cycle_test(ncpus, loops, &ti[1]))
> + printf("Raw cycle is not stable\n");
> + else
> + printf("Raw cycle is stable\n");
> +
> + pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
> + printf("Monotonic cycle test:\n");
> + nerr += cycle_test(ncpus, loops, &ti[0]);
> +
> + for (i = 0; i < ncpus; ++i)
> + on_cpu(i, kvm_clock_clear, (void *)0);
> +
> + return nerr > 0 ? 1 : 0;

another interesting bit of information is the total time taken by
the first cycle_test, compared to the second (They do the same amount
of loops anyway, so no need for further math). We are all pretty sure
the lack of a stable bit will influence kvm clock performance, but
nobody measured by how much yet (in big, big boxes.)