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x86/hyperv: Micro-optimize send_ipi_one()

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When sending an IPI to a single CPU there is no need to deal with cpumasks.

With 2 CPU guest on WS2019 a minor (like 3%, 8043 -> 7761 CPU cycles)
improvement with smp_call_function_single() loop benchmark can be seeb. The
optimization, however, is tiny and straitforward. Also, send_ipi_one() is
important for PV spinlock kick.

Switching to the regular APIC IPI send for CPU > 64 case does not make
sense as it is twice as expesive (12650 CPU cycles for __send_ipi_mask_ex()
call, 26000 for orig_apic.send_IPI(cpu, vector)).

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Link: https://lkml.kernel.org/r/20191027151938.7296-1-vkuznets@redhat.com
This commit is contained in:
Vitaly Kuznetsov 2019-10-27 16:19:38 +01:00 committed by Thomas Gleixner
parent 83527ef7ab
commit b264f57fde
2 changed files with 28 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/hyperv/hv_apic.c
View File

@ -194,10 +194,20 @@ do_ex_hypercall:
static bool __send_ipi_one(int cpu, int vector)
{
struct cpumask mask = CPU_MASK_NONE;
int vp = hv_cpu_number_to_vp_number(cpu);
cpumask_set_cpu(cpu, &mask);
return __send_ipi_mask(&mask, vector);
trace_hyperv_send_ipi_one(cpu, vector);
if (!hv_hypercall_pg || (vp == VP_INVAL))
return false;
if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
return false;
if (vp >= 64)
return __send_ipi_mask_ex(cpumask_of(cpu), vector);
return !hv_do_fast_hypercall16(HVCALL_SEND_IPI, vector, BIT_ULL(vp));
}
static void hv_send_ipi(int cpu, int vector)

15
arch/x86/include/asm/trace/hyperv.h
View File

@ -71,6 +71,21 @@ TRACE_EVENT(hyperv_send_ipi_mask,
__entry->ncpus, __entry->vector)
);
TRACE_EVENT(hyperv_send_ipi_one,
TP_PROTO(int cpu,
int vector),
TP_ARGS(cpu, vector),
TP_STRUCT__entry(
__field(int, cpu)
__field(int, vector)
),
TP_fast_assign(__entry->cpu = cpu;
__entry->vector = vector;
),
TP_printk("cpu %d vector %x",
__entry->cpu, __entry->vector)
);
#endif /* CONFIG_HYPERV */
#undef TRACE_INCLUDE_PATH