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Subject[PATCH 0/5] KVM: arm64: vcpu preempted check support
Date
From: Zengruan Ye <yezengruan@huawei.com>

This patch set aims to support the vcpu_is_preempted() functionality
under KVM/arm64, which allowing the guest to obtain the vcpu is
currently running or not. This will enhance lock performance on
overcommitted hosts (more runnable vcpus than physical cpus in the
system) as doing busy waits for preempted vcpus will hurt system
performance far worse than early yielding.

We have observed some performace improvements in uninx benchmark tests.

unix benchmark result:
host: kernel 5.5.0-rc1, HiSilicon Kunpeng920, 8 cpus
guest: kernel 5.5.0-rc1, 16 vcpus

test-case | after-patch | before-patch
----------------------------------------+-------------------+------------------
Dhrystone 2 using register variables | 334600751.0 lps | 335319028.3 lps
Double-Precision Whetstone | 32856.1 MWIPS | 32849.6 MWIPS
Execl Throughput | 3662.1 lps | 2718.0 lps
File Copy 1024 bufsize 2000 maxblocks | 432906.4 KBps | 158011.8 KBps
File Copy 256 bufsize 500 maxblocks | 116023.0 KBps | 37664.0 KBps
File Copy 4096 bufsize 8000 maxblocks | 1432769.8 KBps | 441108.8 KBps
Pipe Throughput | 6405029.6 lps | 6021457.6 lps
Pipe-based Context Switching | 185872.7 lps | 184255.3 lps
Process Creation | 4025.7 lps | 3706.6 lps
Shell Scripts (1 concurrent) | 6745.6 lpm | 6436.1 lpm
Shell Scripts (8 concurrent) | 998.7 lpm | 931.1 lpm
System Call Overhead | 3913363.1 lps | 3883287.8 lps
----------------------------------------+-------------------+------------------
System Benchmarks Index Score | 1835.1 | 1327.6

Zengruan Ye (5):
KVM: arm64: Document PV-lock interface
KVM: arm64: Implement PV_LOCK_FEATURES call
KVM: arm64: Support pvlock preempted via shared structure
KVM: arm64: Add interface to support vcpu preempted check
KVM: arm64: Support the vcpu preemption check

Documentation/virt/kvm/arm/pvlock.rst | 31 +++++++++
arch/arm/include/asm/kvm_host.h | 13 ++++
arch/arm64/include/asm/kvm_host.h | 17 +++++
arch/arm64/include/asm/paravirt.h | 15 ++++
arch/arm64/include/asm/pvlock-abi.h | 16 +++++
arch/arm64/include/asm/spinlock.h | 7 ++
arch/arm64/kernel/Makefile | 2 +-
arch/arm64/kernel/paravirt-spinlocks.c | 13 ++++
arch/arm64/kernel/paravirt.c | 95 +++++++++++++++++++++++++-
arch/arm64/kernel/setup.c | 2 +
arch/arm64/kvm/Makefile | 1 +
include/linux/arm-smccc.h | 13 ++++
include/linux/cpuhotplug.h | 1 +
virt/kvm/arm/arm.c | 8 +++
virt/kvm/arm/hypercalls.c | 7 ++
virt/kvm/arm/pvlock.c | 21 ++++++
16 files changed, 260 insertions(+), 2 deletions(-)
create mode 100644 Documentation/virt/kvm/arm/pvlock.rst
create mode 100644 arch/arm64/include/asm/pvlock-abi.h
create mode 100644 arch/arm64/kernel/paravirt-spinlocks.c
create mode 100644 virt/kvm/arm/pvlock.c

--
2.19.1


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