Re: [PATCH v4 0/3] KVM: Introduce dedicated vCPUs hint KVM_HINTS_DEDICATED
2018-03-06 22:39 GMT+08:00 Eduardo Valentin : > Folks, > > On Tue, Feb 13, 2018 at 09:05:39AM +0800, Wanpeng Li wrote: >> This patchset introduces dedicated vCPUs(vCPU pinning, and there is no >> vCPU over-commitment) hint KVM_HINTS_DEDICATED, it has two users now: >> >> 1) Waiman Long mentioned that: >> >> Generally speaking, unfair lock performs well for VMs with a small >> number of vCPUs. Native qspinlock may perform better than pvqspinlock >> if there is vCPU pinning and there is no vCPU over-commitment. >> >> 2) vCPUs are very unlikely to get preempted when they are the only task >>running on a CPU. PV TLB flush is slower that the native flush in that >>case. >> >> v3 -> v4: >> * update feature bit document >> v2 -> v3: >> * a separate table for CPUID[0x4001].EDX bits >> * a new kvm_hint_has_feature macro >> v1 -> v2: >> * update to KVM_HINTS_DEDICATED > > Great to see this has finally moved forward! Thanks for picking it up Wanpeng. > > I would just request to next time at least reference the original thread and > copy the original authors of the patch/idea. Thanks for the original idea, Eduardo! Regards, Wanpeng Li
Re: [PATCH v4 0/3] KVM: Introduce dedicated vCPUs hint KVM_HINTS_DEDICATED
Folks, On Tue, Feb 13, 2018 at 09:05:39AM +0800, Wanpeng Li wrote: > This patchset introduces dedicated vCPUs(vCPU pinning, and there is no > vCPU over-commitment) hint KVM_HINTS_DEDICATED, it has two users now: > > 1) Waiman Long mentioned that: > > Generally speaking, unfair lock performs well for VMs with a small > number of vCPUs. Native qspinlock may perform better than pvqspinlock > if there is vCPU pinning and there is no vCPU over-commitment. > > 2) vCPUs are very unlikely to get preempted when they are the only task >running on a CPU. PV TLB flush is slower that the native flush in that >case. > > v3 -> v4: > * update feature bit document > v2 -> v3: > * a separate table for CPUID[0x4001].EDX bits > * a new kvm_hint_has_feature macro > v1 -> v2: > * update to KVM_HINTS_DEDICATED Great to see this has finally moved forward! Thanks for picking it up Wanpeng. I would just request to next time at least reference the original thread and copy the original authors of the patch/idea. Thanks a lot. -- All the best, Eduardo Valentin
[PATCH v4 0/3] KVM: Introduce dedicated vCPUs hint KVM_HINTS_DEDICATED
This patchset introduces dedicated vCPUs(vCPU pinning, and there is no vCPU over-commitment) hint KVM_HINTS_DEDICATED, it has two users now: 1) Waiman Long mentioned that: Generally speaking, unfair lock performs well for VMs with a small number of vCPUs. Native qspinlock may perform better than pvqspinlock if there is vCPU pinning and there is no vCPU over-commitment. 2) vCPUs are very unlikely to get preempted when they are the only task running on a CPU. PV TLB flush is slower that the native flush in that case. v3 -> v4: * update feature bit document v2 -> v3: * a separate table for CPUID[0x4001].EDX bits * a new kvm_hint_has_feature macro v1 -> v2: * update to KVM_HINTS_DEDICATED Wanpeng Li (3): KVM: Introduce dedicated vCPUs hint KVM_HINTS_DEDICATED KVM: X86: Choose qspinlock when dedicated vCPUs available KVM: X86: Don't use PV TLB flush with dedicated vCPUs and steal time disabled Documentation/virtual/kvm/cpuid.txt | 15 +-- arch/mips/include/asm/kvm_para.h | 5 + arch/powerpc/include/asm/kvm_para.h | 5 + arch/s390/include/asm/kvm_para.h | 5 + arch/x86/include/asm/kvm_para.h | 6 ++ arch/x86/include/uapi/asm/kvm_para.h | 8 ++-- arch/x86/kernel/kvm.c| 18 -- include/asm-generic/kvm_para.h | 5 + include/linux/kvm_para.h | 5 + 9 files changed, 66 insertions(+), 6 deletions(-) -- 2.7.4
