From: Ricardo Koller <ricarkol@google.com>
To: pbonzini@redhat.com, maz@kernel.org, oupton@google.com,
yuzenghui@huawei.com, dmatlack@google.com
Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, qperret@google.com,
catalin.marinas@arm.com, andrew.jones@linux.dev,
seanjc@google.com, alexandru.elisei@arm.com,
suzuki.poulose@arm.com, eric.auger@redhat.com, gshan@redhat.com,
reijiw@google.com, rananta@google.com, bgardon@google.com,
ricarkol@gmail.com, Ricardo Koller <ricarkol@google.com>,
Shaoqin Huang <shahuang@redhat.com>
Subject: [PATCH v6 09/12] KVM: arm64: Split huge pages when dirty logging is enabled
Date: Tue, 7 Mar 2023 03:45:52 +0000 [thread overview]
Message-ID: <20230307034555.39733-10-ricarkol@google.com> (raw)
In-Reply-To: <20230307034555.39733-1-ricarkol@google.com>
Split huge pages eagerly when enabling dirty logging. The goal is to
avoid doing it while faulting on write-protected pages, which
negatively impacts guest performance.
A memslot marked for dirty logging is split in 1GB pieces at a time.
This is in order to release the mmu_lock and give other kernel threads
the opportunity to run, and also in order to allocate enough pages to
split a 1GB range worth of huge pages (or a single 1GB huge page).
Note that these page allocations can fail, so eager page splitting is
best-effort. This is not a correctness issue though, as huge pages
can still be split on write-faults.
The benefits of eager page splitting are the same as in x86, added
with commit a3fe5dbda0a4 ("KVM: x86/mmu: Split huge pages mapped by
the TDP MMU when dirty logging is enabled"). For example, when running
dirty_log_perf_test with 64 virtual CPUs (Ampere Altra), 1GB per vCPU,
50% reads, and 2MB HugeTLB memory, the time it takes vCPUs to access
all of their memory after dirty logging is enabled decreased by 44%
from 2.58s to 1.42s.
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
---
arch/arm64/kvm/mmu.c | 118 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 116 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 898985b09321..b1b8da5f8b6c 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -31,14 +31,21 @@ static phys_addr_t __ro_after_init hyp_idmap_vector;
static unsigned long __ro_after_init io_map_base;
-static phys_addr_t stage2_range_addr_end(phys_addr_t addr, phys_addr_t end)
+static phys_addr_t __stage2_range_addr_end(phys_addr_t addr, phys_addr_t end,
+ phys_addr_t size)
{
- phys_addr_t size = kvm_granule_size(KVM_PGTABLE_MIN_BLOCK_LEVEL);
phys_addr_t boundary = ALIGN_DOWN(addr + size, size);
return (boundary - 1 < end - 1) ? boundary : end;
}
+static phys_addr_t stage2_range_addr_end(phys_addr_t addr, phys_addr_t end)
+{
+ phys_addr_t size = kvm_granule_size(KVM_PGTABLE_MIN_BLOCK_LEVEL);
+
+ return __stage2_range_addr_end(addr, end, size);
+}
+
/*
* Release kvm_mmu_lock periodically if the memory region is large. Otherwise,
* we may see kernel panics with CONFIG_DETECT_HUNG_TASK,
@@ -75,6 +82,77 @@ static int stage2_apply_range(struct kvm_s2_mmu *mmu, phys_addr_t addr,
#define stage2_apply_range_resched(mmu, addr, end, fn) \
stage2_apply_range(mmu, addr, end, fn, true)
+static bool need_topup_split_page_cache_or_resched(struct kvm *kvm, uint64_t min)
+{
+ struct kvm_mmu_memory_cache *cache;
+
+ if (need_resched() || rwlock_needbreak(&kvm->mmu_lock))
+ return true;
+
+ cache = &kvm->arch.mmu.split_page_cache;
+ return kvm_mmu_memory_cache_nr_free_objects(cache) < min;
+}
+
+/*
+ * Get the maximum number of page-tables needed to split a range of
+ * blocks into PAGE_SIZE PTEs. It assumes the range is already mapped
+ * at the PMD level, or at the PUD level if allowed.
+ */
+static int kvm_mmu_split_nr_page_tables(u64 range)
+{
+ int n = 0;
+
+ if (KVM_PGTABLE_MIN_BLOCK_LEVEL < 2)
+ n += DIV_ROUND_UP_ULL(range, PUD_SIZE);
+ n += DIV_ROUND_UP_ULL(range, PMD_SIZE);
+ return n;
+}
+
+static int kvm_mmu_split_huge_pages(struct kvm *kvm, phys_addr_t addr,
+ phys_addr_t end)
+{
+ struct kvm_mmu_memory_cache *cache;
+ struct kvm_pgtable *pgt;
+ int ret;
+ u64 next;
+ u64 chunk_size = kvm->arch.mmu.split_page_chunk_size;
+ int cache_capacity = kvm_mmu_split_nr_page_tables(chunk_size);
+
+ if (chunk_size == 0)
+ return 0;
+
+ lockdep_assert_held_write(&kvm->mmu_lock);
+
+ cache = &kvm->arch.mmu.split_page_cache;
+
+ do {
+ if (need_topup_split_page_cache_or_resched(kvm,
+ cache_capacity)) {
+ write_unlock(&kvm->mmu_lock);
+ cond_resched();
+ /* Eager page splitting is best-effort. */
+ ret = __kvm_mmu_topup_memory_cache(cache,
+ cache_capacity,
+ cache_capacity);
+ write_lock(&kvm->mmu_lock);
+ if (ret)
+ break;
+ }
+
+ pgt = kvm->arch.mmu.pgt;
+ if (!pgt)
+ return -EINVAL;
+
+ next = __stage2_range_addr_end(addr, end, chunk_size);
+ ret = kvm_pgtable_stage2_split(pgt, addr, next - addr,
+ cache, cache_capacity);
+ if (ret)
+ break;
+ } while (addr = next, addr != end);
+
+ return ret;
+}
+
static bool memslot_is_logging(struct kvm_memory_slot *memslot)
{
return memslot->dirty_bitmap && !(memslot->flags & KVM_MEM_READONLY);
@@ -773,6 +851,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
void kvm_uninit_stage2_mmu(struct kvm *kvm)
{
kvm_free_stage2_pgd(&kvm->arch.mmu);
+ kvm_mmu_free_memory_cache(&kvm->arch.mmu.split_page_cache);
}
static void stage2_unmap_memslot(struct kvm *kvm,
@@ -999,6 +1078,31 @@ static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
stage2_wp_range(&kvm->arch.mmu, start, end);
}
+/**
+ * kvm_mmu_split_memory_region() - split the stage 2 blocks into PAGE_SIZE
+ * pages for memory slot
+ * @kvm: The KVM pointer
+ * @slot: The memory slot to split
+ *
+ * Acquires kvm->mmu_lock. Called with kvm->slots_lock mutex acquired,
+ * serializing operations for VM memory regions.
+ */
+static void kvm_mmu_split_memory_region(struct kvm *kvm, int slot)
+{
+ struct kvm_memslots *slots = kvm_memslots(kvm);
+ struct kvm_memory_slot *memslot = id_to_memslot(slots, slot);
+ phys_addr_t start, end;
+
+ lockdep_assert_held(&kvm->slots_lock);
+
+ start = memslot->base_gfn << PAGE_SHIFT;
+ end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;
+
+ write_lock(&kvm->mmu_lock);
+ kvm_mmu_split_huge_pages(kvm, start, end);
+ write_unlock(&kvm->mmu_lock);
+}
+
/*
* kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
* dirty pages.
@@ -1790,6 +1894,16 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
return;
kvm_mmu_wp_memory_region(kvm, new->id);
+ kvm_mmu_split_memory_region(kvm, new->id);
+ } else {
+ /*
+ * Free any leftovers from the eager page splitting cache. Do
+ * this when deleting, moving, disabling dirty logging, or
+ * creating the memslot (a nop). Doing it for deletes makes
+ * sure we don't leak memory, and there's no need to keep the
+ * cache around for any of the other cases.
+ */
+ kvm_mmu_free_memory_cache(&kvm->arch.mmu.split_page_cache);
}
}
--
2.40.0.rc0.216.gc4246ad0f0-goog
next prev parent reply other threads:[~2023-03-07 3:46 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-07 3:45 [PATCH v6 00/12] Implement Eager Page Splitting for ARM Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 01/12] KVM: arm64: Rename free_removed to free_unlinked Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 02/12] KVM: arm64: Add KVM_PGTABLE_WALK ctx->flags for skipping BBM and CMO Ricardo Koller
2023-03-12 10:49 ` Marc Zyngier
2023-03-13 18:49 ` Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 03/12] KVM: arm64: Add helper for creating unlinked stage2 subtrees Ricardo Koller
2023-03-12 11:06 ` Marc Zyngier
2023-03-13 22:23 ` Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 04/12] KVM: arm64: Add kvm_pgtable_stage2_split() Ricardo Koller
2023-03-12 11:35 ` Marc Zyngier
2023-03-13 23:58 ` Ricardo Koller
2023-03-15 18:09 ` Marc Zyngier
2023-03-15 18:51 ` Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 05/12] KVM: arm64: Refactor kvm_arch_commit_memory_region() Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 06/12] KVM: arm64: Add kvm_uninit_stage2_mmu() Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 07/12] KVM: arm64: Export kvm_are_all_memslots_empty() Ricardo Koller
2023-03-12 11:39 ` Marc Zyngier
2023-03-13 15:18 ` Sean Christopherson
2023-03-14 10:18 ` Marc Zyngier
2023-03-15 21:00 ` Sean Christopherson
2023-03-07 3:45 ` [PATCH v6 08/12] KVM: arm64: Add KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE Ricardo Koller
2023-03-12 11:56 ` Marc Zyngier
2023-03-24 7:41 ` Ricardo Koller
2023-03-29 4:50 ` Reiji Watanabe
2023-04-10 20:04 ` Ricardo Koller
2023-03-07 3:45 ` Ricardo Koller [this message]
2023-03-12 12:54 ` [PATCH v6 09/12] KVM: arm64: Split huge pages when dirty logging is enabled Marc Zyngier
2023-04-10 18:32 ` Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 10/12] KVM: arm64: Open-code kvm_mmu_write_protect_pt_masked() Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 11/12] KVM: arm64: Split huge pages during KVM_CLEAR_DIRTY_LOG Ricardo Koller
2023-03-12 13:01 ` Marc Zyngier
2023-04-10 18:26 ` Ricardo Koller
2023-03-07 3:45 ` [PATCH v6 12/12] KVM: arm64: Use local TLBI on permission relaxation Ricardo Koller
2023-03-12 13:22 ` Marc Zyngier
2023-04-10 18:22 ` Ricardo Koller
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