From: Harsh Prateek Bora <harshpb@linux.ibm.com>
To: Nicholas Piggin <npiggin@gmail.com>, qemu-ppc@nongnu.org
Cc: qemu-devel@nongnu.org, BALATON Zoltan <balaton@eik.bme.hu>,
David Gibson <david@gibson.dropbear.id.au>,
Daniel Henrique Barboza <danielhb413@gmail.com>
Subject: Re: [PATCH] spapr: avoid overhead of finding vhyp class in critical operations
Date: Tue, 12 Mar 2024 14:26:21 +0530 [thread overview]
Message-ID: <672bd14a-235c-40e3-a859-d822f1b063cd@linux.ibm.com> (raw)
In-Reply-To: <CZRN44HD20CR.33XSLDXL84FZH@wheely>
On 3/12/24 14:18, Nicholas Piggin wrote:
> 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.
I agree, but not just it appears a bit odd, my only worry is if a future
change cause vhyp_class to be NULL before the control reaches here, this
check wont really serve the purpose. Anyways, not a mandatory
requirement for now, so I shall leave it to your choice.
regards,
Harsh
>
> 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);
>
>
next prev parent reply other threads:[~2024-03-12 8:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-24 7:33 [PATCH] spapr: avoid overhead of finding vhyp class in critical operations Nicholas Piggin
2024-02-26 3:01 ` David Gibson
2024-03-12 6:38 ` Harsh Prateek Bora
2024-03-12 8:48 ` Nicholas Piggin
2024-03-12 8:56 ` Harsh Prateek Bora [this message]
2024-03-12 10:40 ` Nicholas Piggin
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