[PATCH v2 0/4] KVM: optimize the kvm_vcpu_on_spin

Longpeng(Mike)
2017-08-08T04:06:10Z

This is a simple optimization for kvm_vcpu_on_spin, the
main idea is described in patch-1's commit msg.

I did some tests base on the RFC version, the result shows
that it can improves the performance slightly.

== Geekbench-3.4.1 ==
VM1: 8U,4G, vcpu(0...7) is 1:1 pinned to pcpu(6...11,18,19)
running Geekbench-3.4.1 *10 truns*
VM2/VM3/VM4: configure is the same as VM1
stress each vcpu usage(seed by top in guest) to 40%

The comparison of each testcase's score:
(higher is better)
before after improve
Inter
single 1176.7 1179.0 0.2%
multi 3459.5 3426.5 -0.9%
Float
single 1150.5 1150.9 0.0%
multi 3364.5 3391.9 0.8%
Memory(stream)
single 1768.7 1773.1 0.2%
multi 2511.6 2557.2 1.8%
Overall
single 1284.2 1286.2 0.2%
multi 3231.4 3238.4 0.2%

== kernbench-0.42 ==
VM1: 8U,12G, vcpu(0...7) is 1:1 pinned to pcpu(6...11,18,19)
running "kernbench -n 10"
VM2/VM3/VM4: configure is the same as VM1
stress each vcpu usage(seed by top in guest) to 40%

The comparison of 'Elapsed Time':
(sooner is better)
before after improve
load -j4 12.762 12.751 0.1%
load -j32 9.743 8.955 8.1%
load -j 9.688 9.229 4.7%

Physical Machine:
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 24
On-line CPU(s) list: 0-23
Thread(s) per core: 2
Core(s) per socket: 6
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 45
Model name: Intel(R) Xeon(R) CPU E5-2640 0 @ 2.50GHz
Stepping: 7
CPU MHz: 2799.902
BogoMIPS: 5004.67
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 15360K
NUMA node0 CPU(s): 0-5,12-17
NUMA node1 CPU(s): 6-11,18-23

---
Changes since V1:
- split the implementation of s390 & arm. [David]
- refactor the impls according to the suggestion. [Paolo]

Changes since RFC:
- only cache result for X86. [David & Cornlia & Paolo]
- add performance numbers. [David]
- impls arm/s390. [Christoffer & David]
- refactor the impls. [me]

---
Longpeng(Mike) (4):
KVM: add spinlock optimization framework
KVM: X86: implement the logic for spinlock optimization
KVM: s390: implements the kvm_arch_vcpu_in_kernel()
KVM: arm: implements the kvm_arch_vcpu_in_kernel()

arch/arm/kvm/handle_exit.c | 2 +-
arch/arm64/kvm/handle_exit.c | 2 +-
arch/mips/kvm/mips.c | 6 ++++++
arch/powerpc/kvm/powerpc.c | 6 ++++++
arch/s390/kvm/diag.c | 2 +-
arch/s390/kvm/kvm-s390.c | 6 ++++++
arch/x86/include/asm/kvm_host.h | 5 +++++
arch/x86/kvm/hyperv.c | 2 +-
arch/x86/kvm/svm.c | 10 +++++++++-
arch/x86/kvm/vmx.c | 16 +++++++++++++++-
arch/x86/kvm/x86.c | 11 +++++++++++
include/linux/kvm_host.h | 3 ++-
virt/kvm/arm/arm.c | 5 +++++
virt/kvm/kvm_main.c | 4 +++-
14 files changed, 72 insertions(+), 8 deletions(-)

--
1.8.3.1