linux-kernel - Re: [git-pull -tip] x86: Basic AMD Support for performance counters

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Date:	Sun, 1 Mar 2009 13:00:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	x86 maintainers <x86@...nel.org>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [git-pull -tip] x86: Basic AMD Support for performance counters


* Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> 
> > On Sun, 2009-03-01 at 12:30 +0100, Ingo Molnar wrote:
> > > * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> > > 
> > > > On Sun, 2009-03-01 at 09:36 +0100, Ingo Molnar wrote:
> > > > > * Ingo Molnar <mingo@...e.hu> wrote:
> > > > > 
> > > > > > Seems to be working fine, here's the output from an Athlon 64 
> > > > > > 3200+ (Sempron) box:
> > > > > > 
> > > > > >  Performance counter stats for 'ls':
> > > > > > 
> > > > > >       17.420811  task clock ticks     (msecs)
> > > > > > 
> > > > > >               0  CPU migrations       (events)
> > > > > >              12  context switches     (events)
> > > > > >             583  pagefaults           (events)
> > > > > >        29760299  CPU cycles           (events)
> > > > > >        29401642  instructions         (events)
> > > > > >        12698498  cache references     (events)
> > > > > >           66269  cache misses         (events)
> > > > > > 
> > > > > >  Wall-clock time elapsed:   687.999988 msecs
> > > > > 
> > > > > The patches cause a crash on another system - an Opteron system 
> > > > > spontaneous reboots at this point during early bootup:
> > > > > 
> > > > > CPU 0/0x4 -> Node 0
> > > > > tseg: 00cfe00000
> > > > > CPU: Physical Processor ID: 0
> > > > > CPU: Processor Core ID: 0
> > > > > using C1E aware idle routine
> > > > > AMD Performance Monitoring support detected.
> > > > > ... num counters:    4
> > > > > ... value mask:      0000000000000000
> > > > > ... fixed counters:  0
> > > > > ... counter mask:    000000000000000f
> > > > > ACPI: Core revision 20081204
> > > > > ftrace: converting mcount calls to 0f 1f 44 00 00
> > > > > ftrace: allocating 16365 entries in 129 pages
> > > > > Setting APIC routing to physical flat
> > > > > masked ExtINT on CPU#0
> > > > > ENABLING IO
> > > > > [reboot]
> > > > > 
> > > > 
> > > > Can you please share your config file.
> > > 
> > > any config file will crash that box. I used the 64-bit defconfig 
> > > - i.e. 'make ARCH=x86_64 defconfig'.
> > > 
> > 
> > Can you please try this patch:
> > 
> > diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
> > index 266618a..5447cc0 100644
> > --- a/arch/x86/kernel/cpu/perf_counter.c
> > +++ b/arch/x86/kernel/cpu/perf_counter.c
> > @@ -146,7 +146,9 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
> >  	 * Generate PMC IRQs:
> >  	 * (keep 'enabled' bit clear for now)
> >  	 */
> > -	hwc->config = ARCH_PERFMON_EVENTSEL_INT;
> > +	/* Currently Interrupts are disabled on AMD */
> > +	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
> > +		hwc->config = ARCH_PERFMON_EVENTSEL_INT;
> 
> still crashes in a similar way.
> 
> hm, this box has nmi_watchdog=2, and the NMI watchdog uses the 
> PMU too - will disable that.

yep, nmi_watchdog=0 solves the regression. You ought to be able 
to reproduce the same problem by adding nmi_watchdog=2 on your 
testbox.

	Ingo
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