[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Y8np4caG5QeeNjat@google.com>
Date: Fri, 20 Jan 2023 01:09:53 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Like Xu <like.xu.linux@...il.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/8] KVM: x86/pmu: Rewrite reprogram_counters() to
improve performance
On Fri, Nov 11, 2022, Like Xu wrote:
> From: Like Xu <likexu@...cent.com>
>
> A valid pmc is always tested before using pmu->reprogram_pmi. Eliminate
> this part of the redundancy by setting the counter's bitmask directly,
> and in addition, trigger KVM_REQ_PMU only once to save more cpu cycles.
>
> Signed-off-by: Like Xu <likexu@...cent.com>
> ---
> arch/x86/kvm/pmu.h | 11 +++++++++++
> arch/x86/kvm/vmx/pmu_intel.c | 12 ------------
> 2 files changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
> index 2b5376ba66ea..be552c8217a0 100644
> --- a/arch/x86/kvm/pmu.h
> +++ b/arch/x86/kvm/pmu.h
> @@ -189,6 +189,17 @@ static inline void kvm_pmu_request_counter_reprogam(struct kvm_pmc *pmc)
> kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
> }
>
> +static inline void reprogram_counters(struct kvm_pmu *pmu, u64 diff)
> +{
> + int bit;
> +
> + if (diff) {
Prefer this, it's slightly cleaner:
if (!diff)
return;
> + for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX)
> + __set_bit(bit, pmu->reprogram_pmi);
Needs to use the atomic set_bit().
Powered by blists - more mailing lists