[PATCH 82/87] KVM: arm/arm64: vgic-its: Introduce multiple LPI translation caches

From: Xiangyou Xie xiexiangyou@huawei.com

euleros inclusion category: feature feature: ITS translation cache improvements

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Because dist->lpi_list_lock is a perVM lock, when a virtual machine is configured with multiple virtual NIC devices and receives network packets at the same time, dist->lpi_list_lock will become a performance bottleneck.

This patch increases the number of lpi_translation_cache to eight, hashes the cpuid that executes irqfd_wakeup, and chooses which lpi_translation_cache to use.

I tested the impact of virtual interrupt injection time-consuming： Run the iperf command to send UDP packets to the VM: iperf -c $IP -u -b 40m -l 64 -t 6000& The vm just receive UDP traffic. When configure multiple NICs, each NIC receives the above iperf UDP traffic, This may reflect the performance impact of shared resource competition, such as lock.

Observing the delay of virtual interrupt injection: the time spent by the "irqfd_wakeup", "irqfd_inject" function, and kworker context switch. The less the better.

ITS translation cache greatly reduces the delay of interrupt injection compared to kworker thread, because it eliminate wakeup and uncertain scheduling delay: kworker ITS translation cache improved 1 NIC 6.692 us 1.766 us 73.6% 10 NICs 7.536 us 2.574 us 65.8%

Increases the number of lpi_translation_cache reduce lock competition. Multi-interrupt concurrent injections perform better:

ITS translation cache with patch improved 1 NIC 1.766 us 1.694 us 4.1% 10 NICs 2.574 us 1.848 us 28.2%

Signed-off-by: Xiangyou Xie xiexiangyou@huawei.com Reviewed-by: Hailiang Zhang zhang.zhanghailiang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- include/kvm/arm_vgic.h | 13 ++- virt/kvm/arm/vgic/vgic-init.c | 8 +- virt/kvm/arm/vgic/vgic-its.c | 211 +++++++++++++++++++++++++----------------- 3 files changed, 146 insertions(+), 86 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h index eac0150..88142c1 100644 --- a/include/kvm/arm_vgic.h +++ b/include/kvm/arm_vgic.h @@ -44,6 +44,9 @@ #define irq_is_spi(irq) ((irq) >= VGIC_NR_PRIVATE_IRQS && \ (irq) <= VGIC_MAX_SPI)

+/*The number of lpi translation cache lists*/ +#define LPI_TRANS_CACHES_NUM 8 + enum vgic_type { VGIC_V2, /* Good ol' GICv2 */ VGIC_V3, /* New fancy GICv3 */ @@ -173,6 +176,12 @@ struct vgic_io_device { struct kvm_io_device dev; };

+struct its_trans_cache { + /* LPI translation cache */ + struct list_head lpi_cache; + raw_spinlock_t lpi_cache_lock; +}; + struct vgic_its { /* The base address of the ITS control register frame */ gpa_t vgic_its_base; @@ -260,8 +269,8 @@ struct vgic_dist { struct list_head lpi_list_head; int lpi_list_count;

- /* LPI translation cache */ - struct list_head lpi_translation_cache; + /* LPI translation cache array*/ + struct its_trans_cache lpi_translation_cache[LPI_TRANS_CACHES_NUM];

/* used by vgic-debug */ struct vgic_state_iter *iter; diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c index 04bd2e4..683ae45 100644 --- a/virt/kvm/arm/vgic/vgic-init.c +++ b/virt/kvm/arm/vgic/vgic-init.c @@ -63,9 +63,15 @@ void kvm_vgic_early_init(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; + raw_spinlock_t *lpi_lock; + int i;

INIT_LIST_HEAD(&dist->lpi_list_head); - INIT_LIST_HEAD(&dist->lpi_translation_cache); + for (i = 0; i < LPI_TRANS_CACHES_NUM; i++) { + lpi_lock = &dist->lpi_translation_cache[i].lpi_cache_lock; + INIT_LIST_HEAD(&dist->lpi_translation_cache[i].lpi_cache); + raw_spin_lock_init(lpi_lock); + } raw_spin_lock_init(&dist->lpi_list_lock); }

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c index 01bfa57..d5ec21d 100644 --- a/virt/kvm/arm/vgic/vgic-its.c +++ b/virt/kvm/arm/vgic/vgic-its.c @@ -557,13 +557,21 @@ static inline int list_is_first(const struct list_head *list, return list->prev == head; }

+/* Default is 16 cached LPIs per vcpu */ +#define LPI_DEFAULT_PCPU_CACHE_SIZE 16 + static struct vgic_irq *__vgic_its_check_cache(struct vgic_dist *dist, phys_addr_t db, - u32 devid, u32 eventid) + u32 devid, u32 eventid, + int cacheid) { struct vgic_translation_cache_entry *cte; + struct vgic_irq *irq = NULL; + struct list_head *cache_head; + int pos = 0;

- list_for_each_entry(cte, &dist->lpi_translation_cache, entry) { + cache_head = &dist->lpi_translation_cache[cacheid].lpi_cache; + list_for_each_entry(cte, cache_head, entry) { /* * If we hit a NULL entry, there is nothing after this * point. @@ -571,21 +579,25 @@ static struct vgic_irq *__vgic_its_check_cache(struct vgic_dist *dist, if (!cte->irq) break;

- if (cte->db != db || cte->devid != devid || - cte->eventid != eventid) - continue; + pos++;

- /* - * Move this entry to the head, as it is the most - * recently used. - */ - if (!list_is_first(&cte->entry, &dist->lpi_translation_cache)) - list_move(&cte->entry, &dist->lpi_translation_cache); + if (cte->devid == devid && + cte->eventid == eventid && + cte->db == db) { + /* + * Move this entry to the head if the entry at the + * position behind the LPI_DEFAULT_PCPU_CACHE_SIZE * 2 + * of the LRU list, as it is the most recently used. + */ + if (pos > LPI_DEFAULT_PCPU_CACHE_SIZE * 2) + list_move(&cte->entry, cache_head);

- return cte->irq; + irq = cte->irq; + break; + } }

- return NULL; + return irq; }

static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db, @@ -593,11 +605,15 @@ static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db, { struct vgic_dist *dist = &kvm->arch.vgic; struct vgic_irq *irq; - unsigned long flags; + int cpu; + int cacheid;

- raw_spin_lock_irqsave(&dist->lpi_list_lock, flags); - irq = __vgic_its_check_cache(dist, db, devid, eventid); - raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags); + cpu = smp_processor_id(); + cacheid = cpu % LPI_TRANS_CACHES_NUM; + + raw_spin_lock(&dist->lpi_translation_cache[cacheid].lpi_cache_lock); + irq = __vgic_its_check_cache(dist, db, devid, eventid, cacheid); + raw_spin_unlock(&dist->lpi_translation_cache[cacheid].lpi_cache_lock);

return irq; } @@ -610,49 +626,58 @@ static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its, struct vgic_translation_cache_entry *cte; unsigned long flags; phys_addr_t db; + raw_spinlock_t *lpi_lock; + struct list_head *cache_head; + int cacheid;

/* Do not cache a directly injected interrupt */ if (irq->hw) return;

- raw_spin_lock_irqsave(&dist->lpi_list_lock, flags); - - if (unlikely(list_empty(&dist->lpi_translation_cache))) - goto out; - - /* - * We could have raced with another CPU caching the same - * translation behind our back, so let's check it is not in - * already - */ - db = its->vgic_its_base + GITS_TRANSLATER; - if (__vgic_its_check_cache(dist, db, devid, eventid)) - goto out; - - /* Always reuse the last entry (LRU policy) */ - cte = list_last_entry(&dist->lpi_translation_cache, - typeof(*cte), entry); + for (cacheid = 0; cacheid < LPI_TRANS_CACHES_NUM; cacheid++) { + lpi_lock = &dist->lpi_translation_cache[cacheid].lpi_cache_lock; + cache_head = &dist->lpi_translation_cache[cacheid].lpi_cache; + raw_spin_lock_irqsave(lpi_lock, flags); + if (unlikely(list_empty(cache_head))) { + raw_spin_unlock_irqrestore(lpi_lock, flags); + break; + }

- /* - * Caching the translation implies having an extra reference - * to the interrupt, so drop the potential reference on what - * was in the cache, and increment it on the new interrupt. - */ - if (cte->irq) - __vgic_put_lpi_locked(kvm, cte->irq); + /* + * We could have raced with another CPU caching the same + * translation behind our back, so let's check it is not in + * already + */ + db = its->vgic_its_base + GITS_TRANSLATER; + if (__vgic_its_check_cache(dist, db, devid, eventid, cacheid)) { + raw_spin_unlock_irqrestore(lpi_lock, flags); + continue; + }

- vgic_get_irq_kref(irq); + /* Always reuse the last entry (LRU policy) */ + cte = list_last_entry(cache_head, typeof(*cte), entry);

- cte->db = db; - cte->devid = devid; - cte->eventid = eventid; - cte->irq = irq; + /* + * Caching the translation implies having an extra reference + * to the interrupt, so drop the potential reference on what + * was in the cache, and increment it on the new interrupt. + */ + if (cte->irq) { + raw_spin_lock(&dist->lpi_list_lock); + __vgic_put_lpi_locked(kvm, cte->irq); + raw_spin_unlock(&dist->lpi_list_lock); + } + vgic_get_irq_kref(irq);

- /* Move the new translation to the head of the list */ - list_move(&cte->entry, &dist->lpi_translation_cache); + cte->db = db; + cte->devid = devid; + cte->eventid = eventid; + cte->irq = irq;

-out: - raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags); + /* Move the new translation to the head of the list */ + list_move(&cte->entry, cache_head); + raw_spin_unlock_irqrestore(lpi_lock, flags); + } }

void vgic_its_invalidate_cache(struct kvm *kvm) @@ -660,22 +685,29 @@ void vgic_its_invalidate_cache(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; struct vgic_translation_cache_entry *cte; unsigned long flags; + raw_spinlock_t *lpi_lock; + struct list_head *cache_head; + int i;

- raw_spin_lock_irqsave(&dist->lpi_list_lock, flags); - - list_for_each_entry(cte, &dist->lpi_translation_cache, entry) { - /* - * If we hit a NULL entry, there is nothing after this - * point. - */ - if (!cte->irq) - break; - - __vgic_put_lpi_locked(kvm, cte->irq); - cte->irq = NULL; + for (i = 0; i < LPI_TRANS_CACHES_NUM; i++) { + lpi_lock = &dist->lpi_translation_cache[i].lpi_cache_lock; + cache_head = &dist->lpi_translation_cache[i].lpi_cache; + raw_spin_lock_irqsave(lpi_lock, flags); + list_for_each_entry(cte, cache_head, entry) { + /* + * If we hit a NULL entry, there is nothing after this + * point. + */ + if (!cte->irq) + break; + + raw_spin_lock(&dist->lpi_list_lock); + __vgic_put_lpi_locked(kvm, cte->irq); + raw_spin_unlock(&dist->lpi_list_lock); + cte->irq = NULL; + } + raw_spin_unlock_irqrestore(lpi_lock, flags); } - - raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags); }

int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its, @@ -1872,30 +1904,34 @@ static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its, return ret; }

-/* Default is 16 cached LPIs per vcpu */ -#define LPI_DEFAULT_PCPU_CACHE_SIZE 16 - void vgic_lpi_translation_cache_init(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; unsigned int sz; + struct list_head *cache_head; int i; + int cacheid;

- if (!list_empty(&dist->lpi_translation_cache)) - return; + for (cacheid = 0; cacheid < LPI_TRANS_CACHES_NUM; cacheid++) { + cache_head = &dist->lpi_translation_cache[cacheid].lpi_cache; + if (!list_empty(cache_head)) + return; + }

sz = atomic_read(&kvm->online_vcpus) * LPI_DEFAULT_PCPU_CACHE_SIZE;

- for (i = 0; i < sz; i++) { - struct vgic_translation_cache_entry *cte; - - /* An allocation failure is not fatal */ - cte = kzalloc(sizeof(*cte), GFP_KERNEL); - if (WARN_ON(!cte)) - break; - - INIT_LIST_HEAD(&cte->entry); - list_add(&cte->entry, &dist->lpi_translation_cache); + for (cacheid = 0; cacheid < LPI_TRANS_CACHES_NUM; cacheid++) { + cache_head = &dist->lpi_translation_cache[cacheid].lpi_cache; + for (i = 0; i < sz; i++) { + struct vgic_translation_cache_entry *cte; + + /* An allocation failure is not fatal */ + cte = kzalloc(sizeof(*cte), GFP_KERNEL); + if (WARN_ON(!cte)) + break; + INIT_LIST_HEAD(&cte->entry); + list_add(&cte->entry, cache_head); + } } }

@@ -1903,13 +1939,22 @@ void vgic_lpi_translation_cache_destroy(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; struct vgic_translation_cache_entry *cte, *tmp; + unsigned long flags; + raw_spinlock_t *lpi_lock; + struct list_head *cache_head; + int cacheid;

vgic_its_invalidate_cache(kvm);

- list_for_each_entry_safe(cte, tmp, - &dist->lpi_translation_cache, entry) { - list_del(&cte->entry); - kfree(cte); + for (cacheid = 0; cacheid < LPI_TRANS_CACHES_NUM; cacheid++) { + lpi_lock = &dist->lpi_translation_cache[cacheid].lpi_cache_lock; + cache_head = &dist->lpi_translation_cache[cacheid].lpi_cache; + raw_spin_lock_irqsave(lpi_lock, flags); + list_for_each_entry_safe(cte, tmp, cache_head, entry) { + list_del(&cte->entry); + kfree(cte); + } + raw_spin_unlock_irqrestore(lpi_lock, flags); } }