Re: perf top for arm64?

From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: John Garry <john.garry@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>,
	Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	peterz@infradead.org, mingo@redhat.com,
	alexander.shishkin@linux.intel.com, namhyung@kernel.org,
	mark.rutland@arm.com, will@kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Linuxarm <linuxarm@huawei.com>,
	"linux-perf-users@vger.kernel.org"
	<linux-perf-users@vger.kernel.org>
Subject: Re: perf top for arm64?
Date: Tue, 10 Dec 2019 16:51:13 -0300	[thread overview]
Message-ID: <20191210195113.GD13965@kernel.org> (raw)
In-Reply-To: <9a31536b-f266-e305-1107-2f745d0a33e3@huawei.com>

Em Tue, Dec 10, 2019 at 05:17:56PM +0000, John Garry escreveu:
> On 10/12/2019 17:08, Jiri Olsa wrote:
> > On Tue, Dec 10, 2019 at 04:52:52PM +0000, John Garry wrote:
> > > On 10/12/2019 16:36, Jiri Olsa wrote:
> > > > On Tue, Dec 10, 2019 at 04:13:49PM +0000, John Garry wrote:
> > > > > Hi all,
> > > > > 
> > > > > I find to my surprise that "perf top" does not work for arm64:
> > > > > 
> > > > > root@ubuntu:/home/john/linux# tools/perf/perf top
> > > > > Couldn't read the cpuid for this machine: No such file or directory
> > > > 
> > > 
> > > Hi Jirka,
> > > 
> > > > there was recent change that check on cpuid and quits:
> > > >     608127f73779 perf top: Initialize perf_env->cpuid, needed by the per arch annotation init routine
> > > > 
> > > 
> > > ok, this is new code. I obviously didn't check the git history...
> > > 
> > > But, apart from this, there are many other places where get_cpuid() is
> > > called. I wonder what else we're missing out on, and whether we should still
> > > add it.
> > 
> > right, I was just wondering how come vendor events are working for you,
> > but realized we have get_cpuid_str being called in there ;-)
> > 
> > I think we should add it as you have it prepared already,
> > could you post it with bigger changelog that would explain
> > where it's being used for arm?
> 
> ok, I can look to do that.
> 
> But, as you know, we still need to fix perf top for other architectures
> affected.

Right, I need to make that just a pr_debug() message and then check in
the annotation code when that is needed to see if it is set, if not,
then show a popup error message and refuse to do whatever annotation
feature requires that.

Anyway, your patch should make sense and provide info that the ARM64
annotation may use now or in the future.

- Arnaldo