linux-kernel - Re: [GIT PULL] perf tools changes for v6.10

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Date: Sun, 26 May 2024 17:58:38 +0800
From: Leo Yan <leo.yan@...ux.dev>
To: Ian Rogers <irogers@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Clark Williams <williams@...hat.com>,
	Kate Carcia <kcarcia@...hat.com>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Anne Macedo <retpolanne@...teo.net>,
	Bhaskar Chowdhury <unixbhaskar@...il.com>,
	Ethan Adams <j.ethan.adams@...il.com>,
	James Clark <james.clark@....com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	Tycho Andersen <tycho@...ho.pizza>,
	Yang Jihong <yangjihong@...edance.com>
Subject: Re: [GIT PULL] perf tools changes for v6.10

Hi Ian,

On Sat, May 25, 2024 at 11:22:08PM -0700, Ian Rogers wrote:

[...]

> In doing that work the code was tested by IBM for S390 and by Intel,
> but it was fixing an ARM created problem. ARM were the first to have
> BIG.little systems but contributed nothing to the perf tool to handle
> it, even though each core type has a different PMU. ARM BIG.little
> remains broken with the perf tool and when I fix it for them they
> don't review or test the code. ARM changed and left unworking uncore
> PMU naming conventions. ARM don't fix tests for their platform. ARM
> don't help make perf's tests cover their different way of naming PMUs.
> No one is trying to break ARM machines, but when ARM fails to do
> anything other than review their own changes in the perf tree it is
> something of an inevitability.
> 
> Fwiw, I am working on making perf record, perf top, etc. skip events
> on non-core PMUs when they fail to open. It is a rather large and ugly
> change. It is also a holiday weekend and I'm spending a lot of my time
> in it addressing latent ARM problems.

James is in holiday, so I should cover this in time. Sorry that I did
not respond the issue quickly - mainly as I am not familiar with JSON
and perf event part.

I tried to reproduce the issue reported by Linus on my Arm big.LITTLE
system but cannot reproduce it. As I saw Linus mentioned the issue is
related with Arm DSU event, which is absent on my test board.

But your complaint is received well and I am very appreciate your work
(especially in the weekend). I will continue to look into the details
in this thread, and monitor incoming patches and I will verify them.

Thanks,
Leo