linux-kernel - Re: [PATCH 6/9] perf report: Support instruction latency

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Date:   Fri, 5 Feb 2021 09:38:04 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Yao Jin <yao.jin@...ux.intel.com>, maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH 6/9] perf report: Support instruction latency



On 2/5/2021 6:08 AM, Namhyung Kim wrote:
> On Wed, Feb 3, 2021 at 5:14 AM <kan.liang@...ux.intel.com> wrote:
>>
>> From: Kan Liang <kan.liang@...ux.intel.com>
>>
>> The instruction latency information can be recorded on some platforms,
>> e.g., the Intel Sapphire Rapids server. With both memory latency
>> (weight) and the new instruction latency information, users can easily
>> locate the expensive load instructions, and also understand the time
>> spent in different stages. The users can optimize their applications
>> in different pipeline stages.
>>
>> The 'weight' field is shared among different architectures. Reusing the
>> 'weight' field may impacts other architectures. Add a new field to store
>> the instruction latency.
>>
>> Like the 'weight' support, introduce a 'ins_lat' for the global
>> instruction latency, and a 'local_ins_lat' for the local instruction
>> latency version.
> 
> Could you please clarify the difference between the global latency
> and the local latency?
>

The global means the total latency.
The local means average latency, aka total / number of samples.

Thanks,
Kan