ping, On Thu, 6 Dec 2018 at 15:58, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: > > From: Wanpeng Li <wanpengli@xxxxxxxxxxx> > > Last year guys from huawei reported that the call of memory_global_dirty_log_start/stop() > takes 13s for 4T memory and cause guest freeze too long which increases the unacceptable > migration downtime. [1] [2] > > Guangrong pointed out: > > | collapsible_sptes zaps 4k mappings to make memory-read happy, it is not > | required by the semanteme of KVM_SET_USER_MEMORY_REGION and it is not > | urgent for vCPU's running, it could be done in a separate thread and use > | lock-break technology. > > [1] https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg05249.html > [2] https://www.mail-archive.com/qemu-devel@xxxxxxxxxx/msg449994.html > > Several TB memory guest is common now after NVDIMM is deployed in cloud environment. > This patch utilizes worker thread to zap collapsible sptes in order to lazy collapse > small sptes into large sptes during roll-back after live migration fails. > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx> > --- > arch/x86/include/asm/kvm_host.h | 3 +++ > arch/x86/kvm/mmu.c | 37 ++++++++++++++++++++++++++++++++----- > arch/x86/kvm/x86.c | 4 ++++ > 3 files changed, 39 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index fbda5a9..dde32f9 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -892,6 +892,8 @@ struct kvm_arch { > u64 master_cycle_now; > struct delayed_work kvmclock_update_work; > struct delayed_work kvmclock_sync_work; > + struct delayed_work kvm_mmu_zap_collapsible_sptes_work; > + bool zap_in_progress; > > struct kvm_xen_hvm_config xen_hvm_config; > > @@ -1247,6 +1249,7 @@ void kvm_mmu_zap_all(struct kvm *kvm); > void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, struct kvm_memslots *slots); > unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm); > void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages); > +void zap_collapsible_sptes_fn(struct work_struct *work); > > int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3); > bool pdptrs_changed(struct kvm_vcpu *vcpu); > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 7c03c0f..fe87dd3 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -5679,14 +5679,41 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm, > return need_tlb_flush; > } > > +void zap_collapsible_sptes_fn(struct work_struct *work) > +{ > + struct kvm_memory_slot *memslot; > + struct kvm_memslots *slots; > + struct delayed_work *dwork = to_delayed_work(work); > + struct kvm_arch *ka = container_of(dwork, struct kvm_arch, > + kvm_mmu_zap_collapsible_sptes_work); > + struct kvm *kvm = container_of(ka, struct kvm, arch); > + int i; > + > + mutex_lock(&kvm->slots_lock); > + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > + spin_lock(&kvm->mmu_lock); > + slots = __kvm_memslots(kvm, i); > + kvm_for_each_memslot(memslot, slots) { > + slot_handle_leaf(kvm, (struct kvm_memory_slot *)memslot, > + kvm_mmu_zap_collapsible_spte, true); > + if (need_resched() || spin_needbreak(&kvm->mmu_lock)) > + cond_resched_lock(&kvm->mmu_lock); > + } > + spin_unlock(&kvm->mmu_lock); > + } > + kvm->arch.zap_in_progress = false; > + mutex_unlock(&kvm->slots_lock); > +} > + > +#define KVM_MMU_ZAP_DELAYED (60 * HZ) > void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, > const struct kvm_memory_slot *memslot) > { > - /* FIXME: const-ify all uses of struct kvm_memory_slot. */ > - spin_lock(&kvm->mmu_lock); > - slot_handle_leaf(kvm, (struct kvm_memory_slot *)memslot, > - kvm_mmu_zap_collapsible_spte, true); > - spin_unlock(&kvm->mmu_lock); > + if (!kvm->arch.zap_in_progress) { > + kvm->arch.zap_in_progress = true; > + schedule_delayed_work(&kvm->arch.kvm_mmu_zap_collapsible_sptes_work, > + KVM_MMU_ZAP_DELAYED); > + } > } > > void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm, > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index d029377..c2af289 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9019,6 +9019,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) > > INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn); > INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn); > + INIT_DELAYED_WORK(&kvm->arch.kvm_mmu_zap_collapsible_sptes_work, > + zap_collapsible_sptes_fn); > + kvm->arch.zap_in_progress = false; > > kvm_hv_init_vm(kvm); > kvm_page_track_init(kvm); > @@ -9064,6 +9067,7 @@ void kvm_arch_sync_events(struct kvm *kvm) > { > cancel_delayed_work_sync(&kvm->arch.kvmclock_sync_work); > cancel_delayed_work_sync(&kvm->arch.kvmclock_update_work); > + cancel_delayed_work_sync(&kvm->arch.kvm_mmu_zap_collapsible_sptes_work); > kvm_free_pit(kvm); > } > > -- > 2.7.4 >
