On 08/10/19 05:32, Wanpeng Li wrote:
> On Fri, 4 Oct 2019 at 00:00, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>> ---
>> x86/vmexit.c | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>>
>> diff --git a/x86/vmexit.c b/x86/vmexit.c
>> index 66d3458..81b743b 100644
>> --- a/x86/vmexit.c
>> +++ b/x86/vmexit.c
>> @@ -65,22 +65,30 @@ static void nop(void *junk)
>> }
>>
>> volatile int x = 0;
>> +volatile uint64_t tsc_eoi = 0;
>> +volatile uint64_t tsc_ipi = 0;
>>
>> static void self_ipi_isr(isr_regs_t *regs)
>> {
>> x++;
>> + uint64_t start = rdtsc();
>> eoi();
>> + tsc_eoi += rdtsc() - start;
>> }
>>
>> static void x2apic_self_ipi(int vec)
>> {
>> + uint64_t start = rdtsc();
>> wrmsr(0x83f, vec);
>> + tsc_ipi += rdtsc() - start;
>> }
>>
>> static void apic_self_ipi(int vec)
>> {
>> + uint64_t start = rdtsc();
>> apic_icr_write(APIC_INT_ASSERT | APIC_DEST_SELF | APIC_DEST_PHYSICAL |
>> APIC_DM_FIXED | IPI_TEST_VECTOR, vec);
>> + tsc_ipi += rdtsc() - start;
>> }
>>
>> static void self_ipi_sti_nop(void)
>> @@ -180,7 +188,9 @@ static void x2apic_self_ipi_tpr_sti_hlt(void)
>>
>> static void ipi(void)
>> {
>> + uint64_t start = rdtsc();
>> on_cpu(1, nop, 0);
>> + tsc_ipi += rdtsc() - start;
>> }
>>
>> static void ipi_halt(void)
>> @@ -511,6 +521,7 @@ static bool do_test(struct test *test)
>> }
>>
>> do {
>> + tsc_eoi = tsc_ipi = 0;
>> iterations *= 2;
>> t1 = rdtsc();
>>
>> @@ -523,6 +534,11 @@ static bool do_test(struct test *test)
>> t2 = rdtsc();
>> } while ((t2 - t1) < GOAL);
>> printf("%s %d\n", test->name, (int)((t2 - t1) / iterations));
>> + if (tsc_ipi)
>> + printf(" ipi %s %d\n", test->name, (int)(tsc_ipi / iterations));
>> + if (tsc_eoi)
>> + printf(" eoi %s %d\n", test->name, (int)(tsc_eoi / iterations));
>> +
>> return test->next;
>> }
>
> Thanks for this, do you have more idea to optimize the virtual ipi latency?
I haven't thought about it recently; this was a patch I had written
years ago and I randomly found on my computer. :)
Paolo
