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

From: Jason Wang <jasowang@redhat.com>
To: Zachary Amsden <zamsden@redhat.com>
Cc: mtosatti@redhat.com, avi@redhat.com, kvm@vger.kernel.org,
	glommer@redhat.com
Subject: Re: [PATCH kvm-unit-test 6/6] Add a test for kvm-clock
Date: Sun, 29 Aug 2010 23:29:01 -0400 (EDT)	[thread overview]
Message-ID: <515046340.826321283138941849.JavaMail.root@zmail05.collab.prod.int.phx2.redhat.com> (raw)
In-Reply-To: <18442408.826301283138927321.JavaMail.root@zmail05.collab.prod.int.phx2.redhat.com>

----- "Zachary Amsden" <zamsden@redhat.com> wrote:

> On 08/26/2010 07:49 PM, 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.
> >    
> 
> Technically, it's not monotonic, it's non-decreasing.
> 
> > 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.
> >    
> 
> This in general looks awesome.
> 
> > 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
> > +
> > +struct test_info {
> > +        struct spinlock lock;
> > +        long loops;               /* test loops */
> > +        u64 warps;                /* warp count */
> > +        long long worst;          /* worst warp */
> > +        volatile cycle_t last;    /* last cycle seen by test */
> > +        atomic_t ncpus;           /* number of cpu in the test*/
> > +};
> > +
> > +struct test_info ti[2];
> > +
> > +static int wallclock_test(long sec, long threshold)
> > +{
> > +        int i;
> > +        long ksec, offset;
> > +        struct timespec ts, ts_last;
> > +
> > +        printf("Wallclock test, threshold %ld\n", threshold);
> > +        kvm_get_wallclock(&ts_last);
> > +        ksec = ts_last.sec + ts_last.nsec / NSEC_PER_SEC;
> > +
> > +        offset = ksec - sec;
> > +        printf("Seconds get from host: %ld\n", sec);
> > +        printf("Seconds get from kvmclock: %ld\n", ksec);
> > +
> > +        if (offset>  threshold || offset<  -threshold) {
> > +                printf("Seconds get from kvmclock: %ld\n", ksec);
> > +                return 1;
> > +        }
> > +
> > +        for (i=0; i<  100; i++){
> > +                kvm_get_wallclock(&ts);
> > +                if (ts.nsec != ts_last.nsec || ts.sec !=
> ts_last.sec){
> > +                        printf ("Inconsistent wall clock
> returned!\n");
> > +                        return 1;
> > +                }
> > +        }
> > +        return 0;
> > +}
> > +
> > +static void kvm_clock_test(void *data)
> > +{
> > +        struct test_info *hv_test_info = (struct test_info *)data;
> > +        int i;
> > +
> > +        for (i = 0; i<  hv_test_info->loops; i++){
> > +                cycle_t t0, t1;
> > +                long long delta;
> > +
> > +                spin_lock(&hv_test_info->lock);
> > +                t1 = kvm_clock_read();
> > +                t0 = hv_test_info->last;
> > +                hv_test_info->last = kvm_clock_read();
> > +                spin_unlock(&hv_test_info->lock);
> > +
> > +                delta = t1 - t0;
> > +                if (delta<  0){
> > +                        spin_lock(&hv_test_info->lock);
> > +                        ++hv_test_info->warps;
> > +                        if (delta<  hv_test_info->worst){
> > +                                hv_test_info->worst = delta;
> > +                                printf("Worst warp %lld %\n",
> hv_test_info->worst);
> > +                        }
> > +                        spin_unlock(&hv_test_info->lock);
> > +                }
> > +
> > +                if (!((unsigned long)i&  31))
> > +                        asm volatile("rep; nop");
> > +        }
> > +
> > +        atomic_dec(&hv_test_info->ncpus);
> > +}
> > +
> > +static int cycle_test(int ncpus, long loops, struct test_info *ti)
> > +{
> > +        int i;
> > +
> > +        atomic_set(&ti->ncpus, ncpus);
> > +        ti->loops = loops;
> > +        for (i = ncpus - 1; i>= 0; i--)
> > +                on_cpu_async(i, kvm_clock_test, (void *)ti);
> > +
> > +        /* Wait for the end of other vcpu */
> > +        while(atomic_read(&ti->ncpus))
> > +                ;
> > +
> > +        printf("Total vcpus: %d\n", ncpus);
> > +        printf("Test  loops: %ld\n", ti->loops);
> > +        printf("Total warps: %lld\n", ti->warps);
> > +        printf("Worst warp:  %lld\n", ti->worst);
> > +
> > +        return ti->warps ? 1 : 0;
> > +}
> > +
> > +int main(int ac, char **av)
> > +{
> > +        int ncpus = cpu_count();
> > +        int nerr = 0, i;
> > +        long loops = DEFAULT_TEST_LOOPS;
> > +        long sec = 0;
> > +        long threshold = DEFAULT_THRESHOLD;
> > +
> > +        if (ac>  1)
> > +                loops = atol(av[1]);
> > +        if (ac>  2)
> > +                sec = atol(av[2]);
> > +        if (ac>  3)
> > +                threshold = atol(av[3]);
> > +
> > +        smp_init();
> > +
> > +        if (ncpus>  MAX_CPU)
> > +                ncpus = MAX_CPU;
> > +        for (i = 0; i<  ncpus; ++i)
> > +                on_cpu(i, kvm_clock_init, (void *)0);
> > +
> > +        if (ac>  2)
> > +                nerr += wallclock_test(sec, threshold);
> > +
> > +        printf("Check the stability of raw cycle\n");
> > +        pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT
> > +                          | PVCLOCK_RAW_CYCLE_BIT);
> >    
> 
> What is this RAW_CYCLE_BIT ?  Did I miss something?

RAW_CYCLE_BIT is used to tell the driver return unadjusted cycle value
as could be used to test whether the host could supply a stable cycle.

> 
> 
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