linux-kernel - Re: [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query perfmon_event

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Message-ID: <ca93d33d-a25c-ac04-5b4c-b60380cd4e97@gmail.com>
Date:   Wed, 16 Feb 2022 13:08:49 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>,
        David Dunn <daviddunn@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH kvm/queue v2 2/3] perf: x86/core: Add interface to query
 perfmon_event_map[] directly

On 10/2/2022 11:34 pm, Liang, Kan wrote:
> For the current perf subsystem, a PMU should be shared among different users via 
> the multiplexing mechanism if the resource is limited. No one has full control 
> of a PMU for lifetime. A user can only have the PMU in its given period.

Off-topic, does perf has knobs to disable the default multiplexing mechanism
for individual tasks and enforce a first-come, first-served policy for same 
priority ?

The reported perf data from the multiplexing mechanism may even mislead
the conclusions of subsequent statistically based performance analysis.