From: "Radim Krčmář" <rkrcmar@redhat.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Gleb Natapov <gleb@kernel.org>,
Raghavendra KT <raghavendra.kt@linux.vnet.ibm.com>,
Vinod Chegu <chegu_vinod@hp.com>, Hui-Zhi <hui-zhi.zhao@hp.com>,
Christian Borntraeger <borntraeger@de.ibm.com>
Subject: [PATCH v2 0/6] Dynamic Pause Loop Exiting window.
Date: Wed, 20 Aug 2014 22:53:11 +0200 [thread overview]
Message-ID: <1408567997-21222-1-git-send-email-rkrcmar@redhat.com> (raw)
v1 -> v2:
* squashed [v1 4/9] and [v1 5/9] (clamping)
* dropped [v1 7/9] (CPP abstractions)
* merged core of [v1 9/9] into [v1 4/9] (automatic maximum)
* reworked kernel_param_ops: closer to pure int [v2 6/6]
* introduced ple_window_actual_max & reworked clamping [v2 4/6]
* added seqlock for parameter modifications [v2 6/6]
---
PLE does not scale in its current form. When increasing VCPU count
above 150, one can hit soft lockups because of runqueue lock contention.
(Which says a lot about performance.)
The main reason is that kvm_ple_loop cycles through all VCPUs.
Replacing it with a scalable solution would be ideal, but it has already
been well optimized for various workloads, so this series tries to
alleviate one different major problem while minimizing a chance of
regressions: we have too many useless PLE exits.
Just increasing PLE window would help some cases, but it still spirals
out of control. By increasing the window after every PLE exit, we can
limit the amount of useless ones, so we don't reach the state where CPUs
spend 99% of the time waiting for a lock.
HP confirmed that this series prevents soft lockups and TSC sync errors
on large guests.
Radim Krčmář (6):
KVM: add kvm_arch_sched_in
KVM: x86: introduce sched_in to kvm_x86_ops
KVM: VMX: make PLE window per-VCPU
KVM: VMX: dynamise PLE window
KVM: trace kvm_ple_window
KVM: VMX: runtime knobs for dynamic PLE window
arch/arm/kvm/arm.c | 4 ++
arch/mips/kvm/mips.c | 4 ++
arch/powerpc/kvm/powerpc.c | 4 ++
arch/s390/kvm/kvm-s390.c | 4 ++
arch/x86/include/asm/kvm_host.h | 2 +
arch/x86/kvm/svm.c | 6 ++
arch/x86/kvm/trace.h | 25 ++++++++
arch/x86/kvm/vmx.c | 124 ++++++++++++++++++++++++++++++++++++++--
arch/x86/kvm/x86.c | 6 ++
include/linux/kvm_host.h | 2 +
virt/kvm/kvm_main.c | 2 +
11 files changed, 179 insertions(+), 4 deletions(-)
--
2.0.4
next reply other threads:[~2014-08-20 20:54 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-20 20:53 Radim Krčmář [this message]
2014-08-20 20:53 ` [PATCH v2 1/6] KVM: add kvm_arch_sched_in Radim Krčmář
2014-08-21 8:29 ` Paolo Bonzini
2014-08-21 11:38 ` Radim Krčmář
2014-08-21 12:27 ` Paolo Bonzini
2014-08-21 12:50 ` Radim Krčmář
2014-08-21 13:25 ` Paolo Bonzini
2014-08-20 20:53 ` [PATCH v2 2/6] KVM: x86: introduce sched_in to kvm_x86_ops Radim Krčmář
2014-08-20 20:53 ` [PATCH v2 3/6] KVM: VMX: make PLE window per-VCPU Radim Krčmář
2014-08-21 8:25 ` Paolo Bonzini
2014-08-21 11:38 ` Radim Krčmář
2014-08-20 20:53 ` [PATCH v2 4/6] KVM: VMX: dynamise PLE window Radim Krčmář
2014-08-21 8:24 ` Paolo Bonzini
2014-08-21 11:47 ` Radim Krčmář
2014-08-21 8:26 ` Paolo Bonzini
2014-08-21 11:54 ` Radim Krčmář
2014-08-21 12:29 ` Paolo Bonzini
2014-08-21 12:42 ` Radim Krčmář
2014-08-21 13:18 ` Paolo Bonzini
2014-08-21 13:46 ` Radim Krčmář
2014-08-20 20:53 ` [PATCH v2 5/6] KVM: trace kvm_ple_window Radim Krčmář
2014-08-21 8:29 ` Paolo Bonzini
2014-08-21 11:56 ` Radim Krčmář
2014-08-21 13:22 ` Paolo Bonzini
2014-08-21 13:49 ` Radim Krčmář
2014-08-20 20:53 ` [PATCH v2 6/6] KVM: VMX: runtime knobs for dynamic PLE window Radim Krčmář
2014-08-21 6:49 ` [PATCH v2 0/6] Dynamic Pause Loop Exiting window Zhao, Hui-Zhi (Steven, HPservers-Core-OE-PSC)
2014-08-21 6:49 ` Zhao, Hui-Zhi (Steven, HPservers-Core-OE-PSC)
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