From: Joerg Roedel <joerg.roedel@amd.com>
To: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
LKML <linux-kernel@vger.kernel.org>,
Jason Wang <jasowang@redhat.com>
Subject: Re: perf: record segfaults for cycles event when collecting data on a VM
Date: Wed, 8 Feb 2012 18:44:34 +0100 [thread overview]
Message-ID: <20120208174434.GI22598@amd.com> (raw)
In-Reply-To: <4F32A907.6030505@gmail.com>
On Wed, Feb 08, 2012 at 09:55:35AM -0700, David Ahern wrote:
> perf record -e cycles -p 21483 -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.012 MB perf.data (~503 samples) ]
> Segmentation fault
The problem is similar to the one Jason is seeing. I am working on a fix
right now.
Bottom line is that the perf-tool may receive samples tagged as
GUEST_KERNEL even when guest-sampling is disabled (probably a
race-condition). The perf-tool can not find a valid machine pointer for
such a sample and passes NULL down to the other functions. And some
functions don't seem to handle this.
David, can you try to change the default for perf_guest back to false
amd re-test? Not with 'sleep 1' probably, on my setup it takes a busy
guest and a few seconds to trigger.
Joerg
--
AMD Operating System Research Center
Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
next prev parent reply other threads:[~2012-02-08 17:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-08 16:55 perf: record segfaults for cycles event when collecting data on a VM David Ahern
2012-02-08 17:44 ` Joerg Roedel [this message]
2012-02-08 17:53 ` David Ahern
2012-02-08 17:57 ` Joerg Roedel
2012-02-09 7:30 ` Ingo Molnar
2012-02-09 11:14 ` Joerg Roedel
2012-02-09 13:34 ` Ingo Molnar
2012-02-09 14:32 ` Joerg Roedel
2012-02-09 15:28 ` Joerg Roedel
2012-02-09 15:47 ` David Ahern
2012-02-09 14:43 ` David Ahern
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