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

From: Linus Torvalds
Date: Wed Dec 12 2012 - 22:09:42 EST


On Wed, Dec 12, 2012 at 7:02 PM, David Ahern <dsahern@xxxxxxxxx> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/