Re: [External] : [RFC PATCH v2 1/6] perf vendor events arm64: Add topdown L1 metrics for neoverse-n2

From: John Garry <john.g.garry@oracle.com>
To: Jing Zhang <renyu.zj@linux.alibaba.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
	James Clark <james.clark@arm.com>,
	Mike Leach <mike.leach@linaro.org>, Leo Yan <leo.yan@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
	Andrew Kilroy <andrew.kilroy@arm.com>,
	Shuai Xue <xueshuai@linux.alibaba.com>,
	Zhuo Song <zhuo.song@linux.alibaba.com>
Subject: Re: [External] : [RFC PATCH v2 1/6] perf vendor events arm64: Add topdown L1 metrics for neoverse-n2
Date: Mon, 14 Nov 2022 12:59:30 +0000	[thread overview]
Message-ID: <590ff032-d271-48ee-a4d8-141cc070c335@oracle.com> (raw)
In-Reply-To: <1668411720-3581-2-git-send-email-renyu.zj@linux.alibaba.com>

On 14/11/2022 07:41, Jing Zhang wrote:
> The calculation formula of topdown L1 is from the document:
> https://urldefense.com/v3/__https://documentation-service.arm.com/static/60250c7395978b529036da86?token=__;!!ACWV5N9M2RV99hQ!Ll-Jgvfs0LitTCU-hC6i6BKBVJfhke-pbQq2VoO-gmuSAcglQ3ZqMVMd2r0An_5a3ZDPYmn8zXuCrpUbehwnLHplVQ$  

So since this is a from "standard" document, did you consider putting 
these as an arch std event? I think arch std events would work for 
metrics, like they do for regular events.

> 
> However, due to the wrong count of stall_slot and stall_slot_frontend
> in neoverse-n2, the real stall_slot and real stall_slot_frontend need
> to subtract cpu_cycles, so when calculating the topdownL1 metrics,
> stall_slot and stall_slot_frontend are corrected.

Is there a reference to this? It would be indeed useful to pass a link 
to the n2 doc as these metrics are not part of the arm64 arm. At least I 
assume that they are not there.

> 
> Since neoverse-n2 does not yet support topdown L2, metricgroups such
> as Cache, TLB, Branch, InstructionsMix, and PEutilization will be
> added to further analysis of performance bottlenecks in the following
> patches.
> 

Thanks,
John