From: Gleb Natapov <gleb@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: kvm@vger.kernel.org, mtosatti@redhat.com, mingo@elte.hu,
a.p.zijlstra@chello.nl, acme@ghostprotocols.net
Subject: Re: [PATCH 2/9] KVM: Expose a version 2 architectural PMU to a guests
Date: Thu, 3 Nov 2011 10:31:15 +0200 [thread overview]
Message-ID: <20111103083115.GH14726@redhat.com> (raw)
In-Reply-To: <20111102110945.GC14726@redhat.com>
On Wed, Nov 02, 2011 at 01:09:46PM +0200, Gleb Natapov wrote:
> > > > The user can cause this to be very small (even zero). Can this cause an
> > > > NMI storm?
> > > >
> > > If user will set it to zero then attr.sample_period will always be 0 and
> > > perf will think that the event is non sampling and will use max_period
> > > instead. For a small value greater than zero how is it different from
> > > userspace creating an event with sample_period of 1?
> >
> > I don't know. Does the kernel survive it?
> >
> Need to test, but I do not see anything in the kernel that prevent userspace
> from setting it to any value.
>
You can set sample_period to 1 by providing -c 1 to perf top/record.
Kernel survives it easily since perf subsystem kindly throttles
interrupts for you. You can set max interrupt per event per time tick
in /proc/sys/kernel/perf_event_max_sample_rate.
--
Gleb.
next prev parent reply other threads:[~2011-11-03 8:31 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-30 16:53 [PATCH 0/9] KVM in-guest performance monitoring Gleb Natapov
2011-10-30 16:53 ` [PATCH 1/9] KVM: Expose kvm_lapic_local_deliver() Gleb Natapov
2011-10-30 16:53 ` [PATCH 2/9] KVM: Expose a version 2 architectural PMU to a guests Gleb Natapov
2011-11-01 10:47 ` Avi Kivity
2011-11-01 12:30 ` Gleb Natapov
2011-11-01 13:57 ` Gleb Natapov
2011-11-02 9:54 ` Avi Kivity
2011-11-02 9:56 ` Gleb Natapov
2011-11-02 10:01 ` Avi Kivity
2011-11-02 11:09 ` Gleb Natapov
2011-11-02 12:03 ` Gleb Natapov
2011-11-03 8:31 ` Gleb Natapov [this message]
2011-12-15 12:04 ` [PATCH] KVM: x86: Fix build breakage due to anonymous field initialization Jan Kiszka
2011-12-15 12:08 ` Peter Zijlstra
2011-12-15 12:16 ` Jan Kiszka
2011-12-26 12:38 ` Avi Kivity
2011-10-30 16:53 ` [PATCH 3/9] KVM: Add generic RDPMC support Gleb Natapov
2011-10-30 16:53 ` [PATCH 4/9] KVM: SVM: Intercept RDPMC Gleb Natapov
2011-10-30 16:53 ` [PATCH 5/9] KVM: VMX: " Gleb Natapov
2011-10-30 16:53 ` [PATCH 6/9] perf: expose perf capability to other modules Gleb Natapov
2011-11-01 10:49 ` Avi Kivity
2011-11-01 15:49 ` David Ahern
2011-11-01 16:13 ` Gleb Natapov
2011-11-01 16:20 ` David Ahern
2011-11-01 16:41 ` Gleb Natapov
2011-11-02 7:42 ` Frederic Weisbecker
2011-11-07 14:45 ` Will Deacon
2011-11-10 8:58 ` Frederic Weisbecker
2011-11-10 12:12 ` Jason Wessel
2011-11-15 18:34 ` Frederic Weisbecker
2011-10-30 16:53 ` [PATCH 7/9] KVM: Expose the architectural performance monitoring CPUID leaf Gleb Natapov
2011-11-01 10:51 ` Avi Kivity
2011-11-01 11:25 ` Gleb Natapov
2011-11-01 15:49 ` David Ahern
2011-11-01 16:18 ` Gleb Natapov
2011-11-01 16:24 ` David Ahern
2011-11-01 16:40 ` Gleb Natapov
2011-11-01 17:43 ` David Ahern
2011-11-02 11:18 ` Gleb Natapov
2011-10-30 16:53 ` [PATCH 8/9] KVM: x86 emulator: fix RDPMC privilege check Gleb Natapov
2011-10-30 16:53 ` [PATCH 9/9] KVM: x86 emulator: implement RDPMC (0F 33) Gleb Natapov
2011-10-30 16:57 ` [PATCH 0/9] KVM in-guest performance monitoring Gleb Natapov
-- strict thread matches above, loose matches on Subject: below --
2011-11-03 12:31 Gleb Natapov
2011-11-03 12:31 ` [PATCH 2/9] KVM: Expose a version 2 architectural PMU to a guests Gleb Natapov
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