linux-kernel - Re: [PATCH 3/3] perf_events: add Intel Sandy Bridge offcore

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Date:	Mon, 23 May 2011 21:29:18 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Lin Ming <ming.m.lin@...el.com>
Subject: Re: [PATCH 3/3] perf_events: add Intel Sandy Bridge offcore_response
 low-level support (v3)

On Mon, May 23, 2011 at 6:21 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, 2011-05-23 at 18:12 +0200, Stephane Eranian wrote:
>> This patch adds Intel Sandy Bridge offcore_response support by
>> providing the low-level constraint table for those events.
>>
>> On Sandy Bridge, there are two offcore_response events. Each uses
>> its own dedictated extra register. But those registers are NOT shared
>> between sibling CPUs when HT is on unlike Nehalem/Westmere. They are
>> always private to each CPU. But they still need to be controlled within
>> an event group. All events within an event group must use the same
>> value for the extra MSR. That's not controlled by the second patch in
>> this series.
>>
>> Furthermore on Sandy Bridge, the offcore_response events have NO
>> counter constraints contrary to what the official documentation
>> indicates, so drop the events from the contraint table.
>
> You sending this suggests you actually have a SNB machine, do you also
> happen to know how to use those SNB RSP MSRs? Lin Ming and I were
> wondering how to fill out the extra-regs for
> snb_hw_cache_events_jds[C(LL)].
>
You first need to describe what you want to measure with those generic
events. Then, from that, we can try and find a match with the offcore_resp
bits.
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