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* [PATCH 0/3] KVM: Paravirt remote TLB flush
@ 2017-11-09  1:52 Wanpeng Li
  2017-11-09  1:52 ` [PATCH 1/3] KVM: Add vCPU running/preempted state Wanpeng Li
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Wanpeng Li @ 2017-11-09  1:52 UTC (permalink / raw)
  To: linux-kernel, kvm; +Cc: Paolo Bonzini, Radim Krčmář, Wanpeng Li

Remote flushing api's does a busy wait which is fine in bare-metal
scenario. But with-in the guest, the vcpus might have been pre-empted
or blocked. In this scenario, the initator vcpu would end up
busy-waiting for a long amount of time.

This patch set implements para-virt flush tlbs making sure that it
does not wait for vcpus that are sleeping. And all the sleeping vcpus
flush the tlb on guest enter. Idea was discussed here:
https://lkml.org/lkml/2012/2/20/157

The best result is achieved when we're overcommiting the host by running 
multiple vCPUs on each pCPU. In this case PV tlb flush avoids touching 
vCPUs which are not scheduled and avoid the wait on the main CPU.

In addition, thanks for commit 9e52fc2b50d ("x86/mm: Enable RCU based 
page table freeing (CONFIG_HAVE_RCU_TABLE_FREE=y)")

Test on a Haswell i7 desktop 4 cores (2HT), so 8 pCPUs, running ebizzy in 
one linux guest.

ebizzy -M 
              vanilla    optimized     boost
 8 vCPUs       10152       10083       -0.68% 
16 vCPUs        1224        4866       397.5% 
24 vCPUs        1109        3871       349%
32 vCPUs        1025        3375       329% 

Wanpeng Li (3):
  KVM: Add vCPU running/preempted state
  KVM: Add paravirt remote TLB flush
  KVM: Add flush_on_enter before guest enter

 arch/x86/include/uapi/asm/kvm_para.h |  4 ++++
 arch/x86/kernel/kvm.c                | 31 ++++++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c                   | 12 ++++++++++--
 3 files changed, 44 insertions(+), 3 deletions(-)

-- 
2.7.4

^ permalink raw reply	[flat|nested] 4+ messages in thread
* [PATCH 1/3] KVM: Add vCPU running/preempted state
  2017-11-09  1:52 [PATCH 0/3] KVM: Paravirt remote TLB flush Wanpeng Li
@ 2017-11-09  1:52 ` Wanpeng Li
  2017-11-09  1:52 ` [PATCH 2/3] KVM: Add paravirt remote TLB flush Wanpeng Li
  2017-11-09  1:52 ` [PATCH 3/3] KVM: Add flush_on_enter before guest enter Wanpeng Li
  2 siblings, 0 replies; 4+ messages in thread
From: Wanpeng Li @ 2017-11-09  1:52 UTC (permalink / raw)
  To: linux-kernel, kvm; +Cc: Paolo Bonzini, Radim Krčmář, Wanpeng Li

From: Wanpeng Li <wanpeng.li@hotmail.com>

This patch reuses the preempted field in kvm_steal_time, and will export 
the vcpu running/pre-empted information to the guest from host. This will 
enable guest to intelligently send ipi to running vcpus and set flag for 
pre-empted vcpus. This will prevent waiting for vcpus that are not running.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 arch/x86/include/uapi/asm/kvm_para.h | 3 +++
 arch/x86/kernel/kvm.c                | 2 +-
 arch/x86/kvm/x86.c                   | 4 ++--
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index a965e5b0..ff23ce9 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -50,6 +50,9 @@ struct kvm_steal_time {
 	__u32 pad[11];
 };
 
+#define KVM_VCPU_NOT_PREEMPTED      (0 << 0)
+#define KVM_VCPU_PREEMPTED          (1 << 0)
+
 #define KVM_CLOCK_PAIRING_WALLCLOCK 0
 struct kvm_clock_pairing {
 	__s64 sec;
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 8bb9594..1b1b641 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -608,7 +608,7 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
 {
 	struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
 
-	return !!src->preempted;
+	return !!(src->preempted & KVM_VCPU_PREEMPTED);
 }
 PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d2507c6..1ea28a2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2116,7 +2116,7 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
 		return;
 
-	vcpu->arch.st.steal.preempted = 0;
+	vcpu->arch.st.steal.preempted = KVM_VCPU_NOT_PREEMPTED;
 
 	if (vcpu->arch.st.steal.version & 1)
 		vcpu->arch.st.steal.version += 1;  /* first time write, random junk */
@@ -2887,7 +2887,7 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
 		return;
 
-	vcpu->arch.st.steal.preempted = 1;
+	vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
 
 	kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
 			&vcpu->arch.st.steal.preempted,
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH 2/3] KVM: Add paravirt remote TLB flush
  2017-11-09  1:52 [PATCH 0/3] KVM: Paravirt remote TLB flush Wanpeng Li
  2017-11-09  1:52 ` [PATCH 1/3] KVM: Add vCPU running/preempted state Wanpeng Li
@ 2017-11-09  1:52 ` Wanpeng Li
  2017-11-09  1:52 ` [PATCH 3/3] KVM: Add flush_on_enter before guest enter Wanpeng Li
  2 siblings, 0 replies; 4+ messages in thread
From: Wanpeng Li @ 2017-11-09  1:52 UTC (permalink / raw)
  To: linux-kernel, kvm; +Cc: Paolo Bonzini, Radim Krčmář, Wanpeng Li

From: Wanpeng Li <wanpeng.li@hotmail.com>

Remote flushing api's does a busy wait which is fine in bare-metal
scenario. But with-in the guest, the vcpus might have been pre-empted
or blocked. In this scenario, the initator vcpu would end up
busy-waiting for a long amount of time.

This patch set implements para-virt flush tlbs making sure that it
does not wait for vcpus that are sleeping. And all the sleeping vcpus
flush the tlb on guest enter.

The best result is achieved when we're overcommiting the host by running 
multiple vCPUs on each pCPU. In this case PV tlb flush avoids touching 
vCPUs which are not scheduled and avoid the wait on the main CPU.

Test on a Haswell i7 desktop 4 cores (2HT), so 8 pCPUs, running ebizzy in 
one linux guest.

ebizzy -M 
              vanilla    optimized     boost
 8 vCPUs       10152       10083       -0.68% 
16 vCPUs        1224        4866       397.5% 
24 vCPUs        1109        3871       349%
32 vCPUs        1025        3375       329% 

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 arch/x86/include/uapi/asm/kvm_para.h |  1 +
 arch/x86/kernel/kvm.c                | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index ff23ce9..189e354 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -52,6 +52,7 @@ struct kvm_steal_time {
 
 #define KVM_VCPU_NOT_PREEMPTED      (0 << 0)
 #define KVM_VCPU_PREEMPTED          (1 << 0)
+#define KVM_VCPU_SHOULD_FLUSH       (1 << 1)
 
 #define KVM_CLOCK_PAIRING_WALLCLOCK 0
 struct kvm_clock_pairing {
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 1b1b641..2e2f3ae 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -465,6 +465,33 @@ static void __init kvm_apf_trap_init(void)
 	update_intr_gate(X86_TRAP_PF, async_page_fault);
 }
 
+static void kvm_flush_tlb_others(const struct cpumask *cpumask,
+			const struct flush_tlb_info *info)
+{
+	u8 state;
+	int cpu;
+	struct kvm_steal_time *src;
+	cpumask_t flushmask;
+
+
+	cpumask_copy(&flushmask, cpumask);
+	/*
+	 * We have to call flush only on online vCPUs. And
+	 * queue flush_on_enter for pre-empted vCPUs
+	 */
+	for_each_cpu(cpu, cpumask) {
+		src = &per_cpu(steal_time, cpu);
+		state = src->preempted;
+		if ((state & KVM_VCPU_PREEMPTED)) {
+			if (cmpxchg(&src->preempted, state, state | 1 <<
+				KVM_VCPU_SHOULD_FLUSH))
+					cpumask_clear_cpu(cpu, &flushmask);
+		}
+	}
+
+	native_flush_tlb_others(&flushmask, info);
+}
+
 void __init kvm_guest_init(void)
 {
 	int i;
@@ -484,6 +511,8 @@ void __init kvm_guest_init(void)
 		pv_time_ops.steal_clock = kvm_steal_clock;
 	}
 
+	pv_mmu_ops.flush_tlb_others = kvm_flush_tlb_others;
+
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 		apic_set_eoi_write(kvm_guest_apic_eoi_write);
 
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH 3/3] KVM: Add flush_on_enter before guest enter
  2017-11-09  1:52 [PATCH 0/3] KVM: Paravirt remote TLB flush Wanpeng Li
  2017-11-09  1:52 ` [PATCH 1/3] KVM: Add vCPU running/preempted state Wanpeng Li
  2017-11-09  1:52 ` [PATCH 2/3] KVM: Add paravirt remote TLB flush Wanpeng Li
@ 2017-11-09  1:52 ` Wanpeng Li
  2 siblings, 0 replies; 4+ messages in thread
From: Wanpeng Li @ 2017-11-09  1:52 UTC (permalink / raw)
  To: linux-kernel, kvm; +Cc: Paolo Bonzini, Radim Krčmář, Wanpeng Li

From: Wanpeng Li <wanpeng.li@hotmail.com>

PV-Flush guest would indicate to flush on enter, flush the TLB before
entering and exiting the guest.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 arch/x86/kvm/x86.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1ea28a2..f295360 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2116,7 +2116,13 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
 		return;
 
-	vcpu->arch.st.steal.preempted = KVM_VCPU_NOT_PREEMPTED;
+	if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_NOT_PREEMPTED) ==
+			(KVM_VCPU_SHOULD_FLUSH | KVM_VCPU_PREEMPTED))
+		/*
+		 * Do TLB_FLUSH before entering the guest, its passed
+		 * the stage of request checking
+		 */
+		kvm_x86_ops->tlb_flush(vcpu);
 
 	if (vcpu->arch.st.steal.version & 1)
 		vcpu->arch.st.steal.version += 1;  /* first time write, random junk */
@@ -2887,7 +2893,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
 	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
 		return;
 
-	vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
+	if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_PREEMPTED) ==
+				KVM_VCPU_SHOULD_FLUSH)
+		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 
 	kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
 			&vcpu->arch.st.steal.preempted,
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-11-09  1:53 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-11-09  1:52 [PATCH 0/3] KVM: Paravirt remote TLB flush Wanpeng Li
2017-11-09  1:52 ` [PATCH 1/3] KVM: Add vCPU running/preempted state Wanpeng Li
2017-11-09  1:52 ` [PATCH 2/3] KVM: Add paravirt remote TLB flush Wanpeng Li
2017-11-09  1:52 ` [PATCH 3/3] KVM: Add flush_on_enter before guest enter Wanpeng Li

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