Re: [PATCH v2 0/4] KVM: x86/vPMU: Efficiency optimization by reusing last created perf_event

From: Like Xu <like.xu@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, peterz@infradead.org,
	Jim Mattson <jmattson@google.com>,
	rkrcmar@redhat.com, sean.j.christopherson@intel.com,
	vkuznets@redhat.com, Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	ak@linux.intel.com, wei.w.wang@intel.com, kan.liang@intel.com,
	like.xu@intel.com, ehankland@google.com, arbel.moshe@oracle.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/4] KVM: x86/vPMU: Efficiency optimization by reusing last created perf_event
Date: Mon, 21 Oct 2019 10:26:01 +0800	[thread overview]
Message-ID: <e567902b-4ae6-c880-2ed3-9c9170496cbd@linux.intel.com> (raw)
In-Reply-To: <20191013091533.12971-1-like.xu@linux.intel.com>

On 2019/10/13 17:15, Like Xu wrote:
...

Hi Paolo,

Do you have any concerns or comments for the KVM codes (the last two 
patches) about this vPMU efficiency optimization?

Thanks,
Like Xu

> 
> ---
> Changes in v2:
> - use perf_event_pause() to disable, read, reset by only one lock;
> - use __perf_event_read_value() after _perf_event_disable();
> - replace bitfields with 'u8 event_count; bool need_cleanup;';
> - refine comments and commit messages;
> - fix two issues reported by kbuild test robot for ARCH=[nds32|sh]
> 
> v1:
> https://lore.kernel.org/kvm/20190930072257.43352-1-like.xu@linux.intel.com/
> 
> Like Xu (4):
>    perf/core: Provide a kernel-internal interface to recalibrate event
>      period
>    perf/core: Provide a kernel-internal interface to pause perf_event
>    KVM: x86/vPMU: Reuse perf_event to avoid unnecessary
>      pmc_reprogram_counter
>    KVM: x86/vPMU: Add lazy mechanism to release perf_event per vPMC
> 
>   arch/x86/include/asm/kvm_host.h | 17 +++++++
>   arch/x86/kvm/pmu.c              | 88 ++++++++++++++++++++++++++++++++-
>   arch/x86/kvm/pmu.h              | 15 +++++-
>   arch/x86/kvm/pmu_amd.c          | 14 ++++++
>   arch/x86/kvm/vmx/pmu_intel.c    | 27 ++++++++++
>   arch/x86/kvm/x86.c              | 12 +++++
>   include/linux/perf_event.h      | 10 ++++
>   kernel/events/core.c            | 44 ++++++++++++++---
>   8 files changed, 216 insertions(+), 11 deletions(-)
> 