linux-kernel - Re: [RFC PATCH] perf: Add load latency monitoring on Intel Nehalem/Westmere

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Message-ID: <AANLkTi=LJB1zA-Kt8KE_qaSNga9iJqnR=FMDRq38Zq5_@mail.gmail.com>
Date:	Thu, 23 Dec 2010 11:31:11 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>, paulus <paulus@...ba.org>
Subject: Re: [RFC PATCH] perf: Add load latency monitoring on Intel Nehalem/Westmere

On Thu, Dec 23, 2010 at 11:18 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, 2010-12-23 at 16:59 +0800, Lin Ming wrote:
>> > {L1, L2, L3, RAM}x{snoop, local, remote}x{shared, exclusive} + {unknown,
>> > uncached, IO}
>> >
>> > Which takes all of 5 bits to encode.
>>
>> Do you mean below encoding?
>>
>> bits4 3 2 1 0
>>     + + + + +
>>     | | | | |
>>     | | | {L1, L2, L3, RAM} or {unknown, uncached, IO}
>>     | | |
>>     | {snoop, local, remote, OTHER}
>>     |
>>     {shared, exclusive}
>>
>> If bits(2-3) is OTHER, then bits(0-1) is the encoding of {unknown,
>> uncached, IO}.
>
> That is most certainly a very valid encoding, and a rather nice one at
> that. I hadn't really gone further than: 4*3*2 + 3 < 2^5 :-)
>
> If you also make OTHER=0, then a valid encoding for unknown is also 0,
> which is a nice meaning for 0...
>
I am not sure how you would cover the 9 possibilities for data source as
shown in Table 10-13 using this encoding. Could you show me?
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