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Subject[PATCH v2 0/6] KVM: arm64: VCPU preempted check support
Date
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

Changes from v1:
https://lore.kernel.org/lkml/20191217135549.3240-1-yezengruan@huawei.com/
* Guest kernel no longer allocates the PV lock structure, instead it
is allocated by user space to avoid lifetime issues about kexec.
* Provide VCPU attributes for PV lock.
* Update SMC number of PV lock features.
* Report some basic validation when PV lock init.
* Document preempted field.
* Bunch of typo fixes.

Zengruan Ye (6):
KVM: arm64: Document PV-lock interface
KVM: arm64: Add SMCCC paravirtualised lock calls
KVM: arm64: Support pvlock preempted via shared structure
KVM: arm64: Provide VCPU attributes for PV lock
KVM: arm64: Add interface to support VCPU preempted check
KVM: arm64: Support the VCPU preemption check

Documentation/virt/kvm/arm/pvlock.rst | 63 ++++++++++++
Documentation/virt/kvm/devices/vcpu.txt | 14 +++
arch/arm/include/asm/kvm_host.h | 18 ++++
arch/arm64/include/asm/kvm_host.h | 28 ++++++
arch/arm64/include/asm/paravirt.h | 15 +++
arch/arm64/include/asm/pvlock-abi.h | 16 ++++
arch/arm64/include/asm/spinlock.h | 7 ++
arch/arm64/include/uapi/asm/kvm.h | 2 +
arch/arm64/kernel/Makefile | 2 +-
arch/arm64/kernel/paravirt-spinlocks.c | 13 +++
arch/arm64/kernel/paravirt.c | 121 +++++++++++++++++++++++-
arch/arm64/kernel/setup.c | 2 +
arch/arm64/kvm/Makefile | 1 +
arch/arm64/kvm/guest.c | 9 ++
include/linux/arm-smccc.h | 14 +++
include/linux/cpuhotplug.h | 1 +
include/uapi/linux/kvm.h | 2 +
virt/kvm/arm/arm.c | 8 ++
virt/kvm/arm/hypercalls.c | 8 ++
virt/kvm/arm/pvlock.c | 103 ++++++++++++++++++++
20 files changed, 445 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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