From: "Xu, Like" <like.xu@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sean Christopherson <seanjc@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, Like Xu <like.xu@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jim Mattson <jmattson@google.com>,
kvm@vger.kernel.org,
Thomas Gleixner
"(x86/pti/timer/core/smp/irq/perf/efi/locking/ras/objtool)"
"(x86@kernel.org)" <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU
Date: Mon, 8 Mar 2021 20:01:52 +0800 [thread overview]
Message-ID: <b209d39c-8c0d-93ce-c81d-be2dfea33ad6@intel.com> (raw)
In-Reply-To: <YEXmILSHDNDuMk/N@hirez.programming.kicks-ass.net>
On 2021/3/8 16:53, Peter Zijlstra wrote:
> Still, it calling atomic_switch_perf_msrs() and
> intel_pmu_lbr_is_enabled() when there isn't a PMU at all is of course, a
> complete waste of cycles.
This suggestion is reminiscent of a sad regression of optimizing it:
https://lore.kernel.org/kvm/20200619094046.654019-1-vkuznets@redhat.com/
https://lore.kernel.org/kvm/20210209225653.1393771-1-jmattson@google.com/
next prev parent reply other threads:[~2021-03-08 12:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 22:33 [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU Sean Christopherson
2021-03-08 2:25 ` Xu, Like
2021-03-08 7:12 ` Dmitry Vyukov
2021-03-08 8:35 ` Like Xu
2021-03-08 8:51 ` Dmitry Vyukov
2021-03-08 8:53 ` Peter Zijlstra
2021-03-08 12:01 ` Xu, Like [this message]
2021-03-08 20:40 ` Sean Christopherson
2021-03-09 7:46 ` Peter Zijlstra
2021-03-09 8:45 ` Peter Zijlstra
2021-03-09 17:05 ` Sean Christopherson
2021-03-09 17:07 ` Dmitry Vyukov
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