linux-kernel - Re: [PATCH 2/4] perf: Add mem_hops field in perf_mem_data

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Message-ID: <20211005202015.GC174703@worktop.programming.kicks-ass.net>
Date:   Tue, 5 Oct 2021 22:20:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kajol Jain <kjain@...ux.ibm.com>
Cc:     mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com, acme@...nel.org,
        jolsa@...nel.org, namhyung@...nel.org, ak@...ux.intel.com,
        linux-perf-users@...r.kernel.org, maddy@...ux.ibm.com,
        atrajeev@...ux.vnet.ibm.com, rnsastry@...ux.ibm.com,
        yao.jin@...ux.intel.com, ast@...nel.org, daniel@...earbox.net,
        songliubraving@...com, kan.liang@...ux.intel.com,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        paulus@...ba.org
Subject: Re: [PATCH 2/4] perf: Add mem_hops field in perf_mem_data_src
 structure

On Tue, Oct 05, 2021 at 02:48:35PM +0530, Kajol Jain wrote:
> Going forward, future generation systems can have more hierarchy
> within the chip/package level but currently we don't have any data source
> encoding field in perf, which can be used to represent this level of data.
> 
> Add a new field called 'mem_hops' in the perf_mem_data_src structure
> which can be used to represent intra-chip/package or inter-chip/off-package
> details. This field is of size 3 bits where PERF_MEM_HOPS_{NA, 0..6} value
> can be used to present different hop levels data.
> 
> Also add corresponding macros to define mem_hop field values
> and shift value.
> 
> Currently we define macro for HOPS_0 which corresponds
> to data coming from another core but same chip.
> 
> For ex: Encodings for mem_hops fields with L2 cache:
> 
> L2			- local L2
> L2 | REMOTE | HOPS_0	- remote core, same chip L2

Can we do s/chip/node/ ? Hops are something NUMA related, while chips
come in a bag or something :-)

> +/* hop level */
> +#define PERF_MEM_HOPS_0		0x01 /* remote core, same chip */
> +/* 2-7 available */
> +#define PERF_MEM_HOPS_SHIFT	43