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

Jason Wang
2010-08-30T03:27:06Z

----- "Glauber Costa" <glommer@redhat.com> wrote:

> 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.)

I would add it in next version.