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Re: [PATCH] spapr: avoid overhead of finding vhyp class in critical oper
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From: |
Nicholas Piggin |
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Subject: |
Re: [PATCH] spapr: avoid overhead of finding vhyp class in critical operations |
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Date: |
Tue, 12 Mar 2024 18:48:39 +1000 |
On Tue Mar 12, 2024 at 4:38 PM AEST, Harsh Prateek Bora wrote:
> Hi Nick,
>
> One minor comment below:
>
> On 2/24/24 13:03, Nicholas Piggin wrote:
> > 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.
> >
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > ---
> > This feels a bit ugly, but the performance problem of looking up the
> > class in fast paths can't be ignored. Is there a "nicer" way to get the
> > same result?
> >
> > Thanks,
> > Nick
> >
> > target/ppc/cpu.h | 3 ++-
> > target/ppc/mmu-book3s-v3.h | 4 +---
> > hw/ppc/pegasos2.c | 1 +
> > target/ppc/cpu_init.c | 9 +++------
> > target/ppc/excp_helper.c | 16 ++++------------
> > target/ppc/kvm.c | 4 +---
> > target/ppc/mmu-hash64.c | 16 ++++------------
> > target/ppc/mmu-radix64.c | 4 +---
> > 8 files changed, 17 insertions(+), 40 deletions(-)
> >
> > diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> > index ec14574d14..eb85d9aa71 100644
> > --- a/target/ppc/cpu.h
> > +++ b/target/ppc/cpu.h
> > @@ -1437,6 +1437,7 @@ struct ArchCPU {
> > int vcpu_id;
> > uint32_t compat_pvr;
> > PPCVirtualHypervisor *vhyp;
> > + PPCVirtualHypervisorClass *vhyp_class;
> > void *machine_data;
> > int32_t node_id; /* NUMA node this CPU belongs to */
> > PPCHash64Options *hash64_opts;
> > @@ -1535,7 +1536,7 @@ DECLARE_OBJ_CHECKERS(PPCVirtualHypervisor,
> > PPCVirtualHypervisorClass,
> >
> > static inline bool vhyp_cpu_in_nested(PowerPCCPU *cpu)
> > {
> > - return PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp)->cpu_in_nested(cpu);
> > + return cpu->vhyp_class->cpu_in_nested(cpu);
> > }
> > #endif /* CONFIG_USER_ONLY */
> >
> > diff --git a/target/ppc/mmu-book3s-v3.h b/target/ppc/mmu-book3s-v3.h
> > index 674377a19e..f3f7993958 100644
> > --- a/target/ppc/mmu-book3s-v3.h
> > +++ b/target/ppc/mmu-book3s-v3.h
> > @@ -108,9 +108,7 @@ static inline hwaddr ppc_hash64_hpt_mask(PowerPCCPU
> > *cpu)
> > uint64_t base;
> >
> > if (cpu->vhyp) {
>
> All the checks for cpu->vhyp needs to be changed to check for
> cpu->vhyp_class now, for all such instances.
It wasn't supposed to, because vhyp != NULL implies vhyp_class != NULL.
It's supposed to be an equivalent transformation just changing the
lookup function.
Okay to leave it as is?
Thanks,
Nick
>
> With that,
>
> Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
>
>
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - return vhc->hpt_mask(cpu->vhyp);
> > + return cpu->vhyp_class->hpt_mask(cpu->vhyp);
> > }
> > if (cpu->env.mmu_model == POWERPC_MMU_3_00) {
> > ppc_v3_pate_t pate;
> > diff --git a/hw/ppc/pegasos2.c b/hw/ppc/pegasos2.c
> > index 04d6decb2b..c22e8b336d 100644
> > --- a/hw/ppc/pegasos2.c
> > +++ b/hw/ppc/pegasos2.c
> > @@ -400,6 +400,7 @@ static void pegasos2_machine_reset(MachineState
> > *machine, ShutdownCause reason)
> > machine->fdt = fdt;
> >
> > pm->cpu->vhyp = PPC_VIRTUAL_HYPERVISOR(machine);
> > + pm->cpu->vhyp_class = PPC_VIRTUAL_HYPERVISOR_GET_CLASS(pm->cpu->vhyp);
> > }
> >
> > enum pegasos2_rtas_tokens {
> > diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> > index 9bccddb350..63d0094024 100644
> > --- a/target/ppc/cpu_init.c
> > +++ b/target/ppc/cpu_init.c
> > @@ -6631,6 +6631,7 @@ 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
> > @@ -7224,9 +7225,7 @@ 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);
> > }
> > }
> >
> > @@ -7235,9 +7234,7 @@ 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 */
> > diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> > index 98952de267..445350488c 100644
> > --- a/target/ppc/excp_helper.c
> > +++ b/target/ppc/excp_helper.c
> > @@ -840,9 +840,7 @@ static void powerpc_excp_7xx(PowerPCCPU *cpu, int excp)
> > * HV mode, we need to keep hypercall support.
> > */
> > if (lev == 1 && cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - vhc->hypercall(cpu->vhyp, cpu);
> > + cpu->vhyp_class->hypercall(cpu->vhyp, cpu);
> > powerpc_reset_excp_state(cpu);
> > return;
> > }
> > @@ -1012,9 +1010,7 @@ static void powerpc_excp_74xx(PowerPCCPU *cpu, int
> > excp)
> > * HV mode, we need to keep hypercall support.
> > */
> > if (lev == 1 && cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - vhc->hypercall(cpu->vhyp, cpu);
> > + cpu->vhyp_class->hypercall(cpu->vhyp, cpu);
> > powerpc_reset_excp_state(cpu);
> > return;
> > }
> > @@ -1534,9 +1530,7 @@ static void powerpc_excp_books(PowerPCCPU *cpu, int
> > excp)
> >
> > /* "PAPR mode" built-in hypercall emulation */
> > if (lev == 1 && books_vhyp_handles_hcall(cpu)) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - vhc->hypercall(cpu->vhyp, cpu);
> > + cpu->vhyp_class->hypercall(cpu->vhyp, cpu);
> > powerpc_reset_excp_state(cpu);
> > return;
> > }
> > @@ -1677,10 +1671,8 @@ static void powerpc_excp_books(PowerPCCPU *cpu, int
> > excp)
> > }
> >
> > if ((new_msr & MSR_HVB) && books_vhyp_handles_hv_excp(cpu)) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > /* Deliver interrupt to L1 by returning from the H_ENTER_NESTED
> > call */
> > - vhc->deliver_hv_excp(cpu, excp);
> > + cpu->vhyp_class->deliver_hv_excp(cpu, excp);
> >
> > powerpc_reset_excp_state(cpu);
> >
> > diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> > index 26fa9d0575..5b5b96ab6b 100644
> > --- a/target/ppc/kvm.c
> > +++ b/target/ppc/kvm.c
> > @@ -862,9 +862,7 @@ int kvmppc_put_books_sregs(PowerPCCPU *cpu)
> > sregs.pvr = env->spr[SPR_PVR];
> >
> > if (cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - sregs.u.s.sdr1 = vhc->encode_hpt_for_kvm_pr(cpu->vhyp);
> > + sregs.u.s.sdr1 = cpu->vhyp_class->encode_hpt_for_kvm_pr(cpu->vhyp);
> > } else {
> > sregs.u.s.sdr1 = env->spr[SPR_SDR1];
> > }
> > diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> > index d645c0bb94..196b4b2a48 100644
> > --- a/target/ppc/mmu-hash64.c
> > +++ b/target/ppc/mmu-hash64.c
> > @@ -516,9 +516,7 @@ const ppc_hash_pte64_t *ppc_hash64_map_hptes(PowerPCCPU
> > *cpu,
> > const ppc_hash_pte64_t *hptes;
> >
> > if (cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - return vhc->map_hptes(cpu->vhyp, ptex, n);
> > + return cpu->vhyp_class->map_hptes(cpu->vhyp, ptex, n);
> > }
> > base = ppc_hash64_hpt_base(cpu);
> >
> > @@ -538,9 +536,7 @@ void ppc_hash64_unmap_hptes(PowerPCCPU *cpu, const
> > ppc_hash_pte64_t *hptes,
> > hwaddr ptex, int n)
> > {
> > if (cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - vhc->unmap_hptes(cpu->vhyp, hptes, ptex, n);
> > + cpu->vhyp_class->unmap_hptes(cpu->vhyp, hptes, ptex, n);
> > return;
> > }
> >
> > @@ -820,9 +816,7 @@ static void ppc_hash64_set_r(PowerPCCPU *cpu, hwaddr
> > ptex, uint64_t pte1)
> > hwaddr base, offset = ptex * HASH_PTE_SIZE_64 + HPTE64_DW1_R;
> >
> > if (cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - vhc->hpte_set_r(cpu->vhyp, ptex, pte1);
> > + cpu->vhyp_class->hpte_set_r(cpu->vhyp, ptex, pte1);
> > return;
> > }
> > base = ppc_hash64_hpt_base(cpu);
> > @@ -837,9 +831,7 @@ static void ppc_hash64_set_c(PowerPCCPU *cpu, hwaddr
> > ptex, uint64_t pte1)
> > hwaddr base, offset = ptex * HASH_PTE_SIZE_64 + HPTE64_DW1_C;
> >
> > if (cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc =
> > - PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - vhc->hpte_set_c(cpu->vhyp, ptex, pte1);
> > + cpu->vhyp_class->hpte_set_c(cpu->vhyp, ptex, pte1);
> > return;
> > }
> > base = ppc_hash64_hpt_base(cpu);
> > diff --git a/target/ppc/mmu-radix64.c b/target/ppc/mmu-radix64.c
> > index 5823e039e6..496ba87a95 100644
> > --- a/target/ppc/mmu-radix64.c
> > +++ b/target/ppc/mmu-radix64.c
> > @@ -677,9 +677,7 @@ static bool ppc_radix64_xlate_impl(PowerPCCPU *cpu,
> > vaddr eaddr,
> >
> > /* Get Partition Table */
> > if (cpu->vhyp) {
> > - PPCVirtualHypervisorClass *vhc;
> > - vhc = PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> > - if (!vhc->get_pate(cpu->vhyp, cpu, lpid, &pate)) {
> > + if (!cpu->vhyp_class->get_pate(cpu->vhyp, cpu, lpid, &pate)) {
> > if (guest_visible) {
> > ppc_radix64_raise_hsi(cpu, access_type, eaddr, eaddr,
> > DSISR_R_BADCONFIG);