linux-kernel - Re: [PATCH] perf, x86: add Intel IvyBridge event scheduling constraints

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Message-ID: <CABPqkBS58oMw8Gs7AVN0OMvLuFYH4iXXRHBx3Ep1Mbru=gLVtg@mail.gmail.com>
Date:	Wed, 20 Feb 2013 20:54:08 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH] perf, x86: add Intel IvyBridge event scheduling constraints

On Wed, Feb 20, 2013 at 4:43 PM, Andi Kleen <ak@...ux.intel.com> wrote:
> On Wed, Feb 20, 2013 at 11:15:12AM +0100, Stephane Eranian wrote:
>> Intel IvyBridge processor has different constraints compared
>> to SandyBridge. Therefore it needs its own contraint table.
>> This patch adds the constraint table. Without this patch,
>> the events listed in the patch may not be scheduled correctly
>> and bogus counts may be collected.
>
> Thanks. I ran into this problem too and was about to write
> a similar patch.
>
>> +     INTEL_UEVENT_CONSTRAINT(0x04a3, 0xf), /* CYCLE_ACTIVITY.CYCLES_NO_EXECUTE */
>> +     INTEL_UEVENT_CONSTRAINT(0x05a3, 0xf), /* CYCLE_ACTIVITY.STALLS_L2_PENDING */
>> +     INTEL_UEVENT_CONSTRAINT(0x06a3, 0xf), /* CYCLE_ACTIVITY.STALLS_LDM_PENDING */
>> +     INTEL_UEVENT_CONSTRAINT(0x08a3, 0x4), /* CYCLE_ACTIVITY.CYCLES_L1D_PENDING */
>> +     INTEL_UEVENT_CONSTRAINT(0x0ca3, 0x4), /* CYCLE_ACTIVITY.STALLS_L1D_PENDING */
>
>
> Except for LDM_PENDING the CYCLE_ACTIVITY events have been also added to Sandy Bridge.
> So it should be also added there.
>
As far as I know and I double-checked the documentation I have, there
is no CYCLE_ACTIVITY
event on SNB or SNB-EP.

> In fact I think you can still share the table because it would just add some
> non existent events to Sandy Bridge, which is a noop.
>
I don't see the point of this, except saving a few bytes. Isn't it
better to keep each PMU separate?


> -Andi
>
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