linux-kernel - Re: perf counters: problem with perf record

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Message-ID: <20091115103459.GC24931@elte.hu>
Date:	Sun, 15 Nov 2009 11:34:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Simon K??mpflein <s.kaempflein@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: perf counters: problem with perf record


* Simon K??mpflein <s.kaempflein@....de> wrote:

> Peter Zijlstra schrieb:
> > On Sun, 2009-11-15 at 03:14 +1000, Simon K??mpflein wrote:
> >> Hello,
> >>
> >> I have a problem with the new kernel perf tools in kernel 2.6.31.6 (very
> >> nice tools by the way). I like to monitor the cache-misses of a program.
> >> "perf stat -e cache-misses program" works without problems, but I can't
> >> get "perf record -e cache-misses program" working (even running as root
> >> and CONFIG_PERF_COUNTERS=y):
> >>
> >> Error: perfcounter syscall returned with -1 (Operation not supported)
> >> Fatal: No CONFIG_PERF_COUNTERS=y kernel support configured?
> >>
> >> My CPU is a "Intel(R) Pentium(R) M processor 1.80GHz":
> > 
> > Does the bootlog perchance contain the output of?
> > 
> >         if (!cpu_has_apic) {
> >                 pr_info("no APIC, boot with the \"lapic\" boot parameter
> > to force-enable it.\n");
> >                 pr_info("no hardware sampling interrupt available.\n");
> >                 x86_pmu.apic = 0;
> >         }
> 
> Yes. I didn't realize that it has something to do with the Performance
> Counters because I didn't see that it belongs to the Performance Counter
> output.
> Maybe it's a good idea to add another comment making it clear that the
> performance counters are not fully working in this case. Or detect this
> case in "perf-record" and output a message relating to that.

Ok. Mind sending a patch that changes the message so that it explains it 
all to you more clearly?

> > And does booting with the suggested lapic parameter cure your problems?
> > 
> 
> Yes, thank you!

Great.

You might want to send another patch that allows the .config enabling of 
that lapic boot parameter. It sucks to carry around boot parameters.

	Ingo
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