linux-kernel - Re: [GIT PULL] perf changes for v3.8

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Message-ID: <CA+55aFwD3fFn7iYSnLw7iFk88xPYaVXMQVDyQans77PydgaeGg@mail.gmail.com>
Date:	Wed, 12 Dec 2012 19:09:33 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] perf changes for v3.8

On Wed, Dec 12, 2012 at 7:02 PM, David Ahern <dsahern@...il.com> wrote:
>
> Can you add -v and see if it spits out more info?

No more info.

Sure, it does the usual "do  you have an APIC" message (it does that
without "-v" too), which isn't useful:

  Error: sys_perf_event_open() syscall returned with 95 (Operation not
supported) for event cycles:pp. /bin/dmesg may provide additional
information.

  No hardware sampling interrupt available. No APIC? If so then you
can boot the kernel with the "lapic" boot parameter to force-enable
it.

And yes, I have a local apic. Every single modern CPU does.

The error message is garbage and actively misleading. Lack of an APIC
is just about the *least* likely possible reason for the EOPNOTSUPP
error return.

              Linus
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