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spapr: avoid overhead of finding vhyp class in critical operations

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PPC_VIRTUAL_HYPERVISOR_GET_CLASS is used in critical operations like
interrupts and TLB misses and is quite costly. Running the
kvm-unit-tests sieve program with radix MMU enabled thrashes the TCG
TLB and spends a lot of time in TLB and page table walking code. The
test takes 67 seconds to complete with a lot of time being spent in
code related to finding the vhyp class:

   12.01%  [.] g_str_hash
    8.94%  [.] g_hash_table_lookup
    8.06%  [.] object_class_dynamic_cast
    6.21%  [.] address_space_ldq
    4.94%  [.] __strcmp_avx2
    4.28%  [.] tlb_set_page_full
    4.08%  [.] address_space_translate_internal
    3.17%  [.] object_class_dynamic_cast_assert
    2.84%  [.] ppc_radix64_xlate

Keep a pointer to the class and avoid this lookup. This reduces the
execution time to 40 seconds.

Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
This commit is contained in:
Nicholas Piggin 2024-02-21 20:08:31 +10:00
parent 70581940ca
commit c700b5e162
8 changed files with 17 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files

9
target/ppc/cpu_init.c
View file

@ -6661,6 +6661,7 @@ void cpu_ppc_set_vhyp(PowerPCCPU *cpu, PPCVirtualHypervisor *vhyp)
CPUPPCState *env = &cpu->env;
cpu->vhyp = vhyp;
cpu->vhyp_class = PPC_VIRTUAL_HYPERVISOR_GET_CLASS(vhyp);
/*
* With a virtual hypervisor mode we never allow the CPU to go
@ -7248,9 +7249,7 @@ static void ppc_cpu_exec_enter(CPUState *cs)
PowerPCCPU *cpu = POWERPC_CPU(cs);
if (cpu->vhyp) {
PPCVirtualHypervisorClass *vhc =
PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
vhc->cpu_exec_enter(cpu->vhyp, cpu);
cpu->vhyp_class->cpu_exec_enter(cpu->vhyp, cpu);
}
}
@ -7259,9 +7258,7 @@ static void ppc_cpu_exec_exit(CPUState *cs)
PowerPCCPU *cpu = POWERPC_CPU(cs);
if (cpu->vhyp) {
PPCVirtualHypervisorClass *vhc =
PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
vhc->cpu_exec_exit(cpu->vhyp, cpu);
cpu->vhyp_class->cpu_exec_exit(cpu->vhyp, cpu);
}
}
#endif /* CONFIG_TCG */