From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, vince@deater.net,
eranian@google.com, Arnaldo Carvalho de Melo <acme@infradead.org>,
Borislav Petkov <bp@suse.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 2/2] perf/x86/intel/pt: Fail event creation if VMX operation is on
Date: Wed, 15 Feb 2017 14:37:21 +0100 [thread overview]
Message-ID: <20170215133721.GX6515@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <87d1ejk3jt.fsf@ashishki-desk.ger.corp.intel.com>
On Wed, Feb 15, 2017 at 03:05:10PM +0200, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > On Wed, Feb 15, 2017 at 10:34:58AM +0200, Alexander Shishkin wrote:
> >
> >> Well, we can't make the limitation go away. You'll still have to stop
> >> kvms to get any 'meaningful' PT data.
> >
> > Why would you need to stop all VMs in order to get your !VM data? Sure,
> > you get black holes where the VM runs, but we should be able to see
> > everything else.
>
> No, what I mean is that if you run kvm prior to starting perf record,
> which I assume is the case for acme, your entire session is a black
> hole. The VMXON happens pretty early on, you can open /dev/kvm,
> ioctl(KVM_CREATE_VM) on it and that will do a VMXON already.
kvm_intel has a vmm_exclusive parameter, if you set that to 0 is
_should_ behave much better.
next prev parent reply other threads:[~2017-02-15 13:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-14 13:24 [PATCH 0/2] perf/x86/intel/pt: VMX related updates Alexander Shishkin
2017-02-14 13:24 ` [PATCH 1/2] perf/x86/intel/pt: Fail event scheduling on conflict with VMX Alexander Shishkin
2017-02-14 13:56 ` Peter Zijlstra
2017-02-14 16:17 ` Alexander Shishkin
2017-02-14 16:27 ` Peter Zijlstra
2017-02-14 17:21 ` Alexander Shishkin
2017-02-14 18:38 ` Peter Zijlstra
2017-02-14 19:48 ` Peter Zijlstra
2017-02-15 8:11 ` Alexander Shishkin
2017-02-15 8:53 ` Peter Zijlstra
2017-02-14 13:24 ` [PATCH 2/2] perf/x86/intel/pt: Fail event creation if VMX operation is on Alexander Shishkin
2017-02-14 14:02 ` Peter Zijlstra
2017-02-14 17:47 ` Arnaldo Carvalho de Melo
2017-02-15 8:34 ` Alexander Shishkin
2017-02-15 8:56 ` Peter Zijlstra
2017-02-15 13:05 ` Alexander Shishkin
2017-02-15 13:12 ` Arnaldo Carvalho de Melo
2017-02-15 13:37 ` Peter Zijlstra [this message]
2017-02-15 12:51 ` Arnaldo Carvalho de Melo
2017-02-15 13:09 ` Alexander Shishkin
2017-02-15 13:16 ` Arnaldo Carvalho de Melo
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