Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 0/2] x86/intel_rdt and perf/x86: Fix lack of coordination
 with perf
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     tglx@linutronix.de, mingo@redhat.com, fenghua.yu@intel.com,
        tony.luck@intel.com, vikas.shivappa@linux.intel.com,
        gavin.hindman@intel.com, jithu.joseph@intel.com,
        dave.hansen@intel.com, hpa@zytor.com, x86@kernel.org,
        linux-kernel@vger.kernel.org
References: <cover.1533064851.git.reinette.chatre@intel.com>
 <20180802123923.GJ2530@hirez.programming.kicks-ass.net>
 <1af731f8-b5d3-5aca-af02-575802a961b9@intel.com>
 <20180802161823.GJ2458@hirez.programming.kicks-ass.net>
From:   Reinette Chatre <reinette.chatre@intel.com>
Message-ID: <f990df31-ab75-974e-b142-47af07a33a08@intel.com>
Date:   Thu, 2 Aug 2018 09:44:13 -0700
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.8.0
MIME-Version: 1.0
In-Reply-To: <20180802161823.GJ2458@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 8/2/2018 9:18 AM, Peter Zijlstra wrote:
> On Thu, Aug 02, 2018 at 09:14:10AM -0700, Reinette Chatre wrote:
> 
>> The current implementation does not coordinate with perf and this is
>> what I am trying to fix in this series.
>>
>> I do respect your NAK but it is not clear to me how to proceed after
>> obtaining it. Could you please elaborate on what you would prefer as a
>> solution to ensure accurate measurement of cache-locked data that is
>> better integrated?
> 
> We have an in-kernel interface to perf, use that if you want access to
> the PMU. You will not directly stomp on PMU registers.

I do not see how I can do so without incurring the cache hits and misses
from the data needed and instructions run by this interface. Could you
please share how I can do so and still obtain the accurate measurement
of cache residency of a specific memory region?

Reinette