Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 23 Aug 2019 13:59:46 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ganapatrao Kulkarni <gklkml16@gmail.com>
Cc:     Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Stephane Eranian <eranian@google.com>,
        Ganapatrao Kulkarni <gkulkarni@marvell.com>,
        Jayachandran Chandrasekharan Nair <jnair@marvell.com>
Subject: Re: [PATCH] perf cgroups: Don't rotate events for cgroups
 unnecessarily
Message-ID: <20190823115946.GM2349@hirez.programming.kicks-ass.net>
References: <20190601082722.44543-1-irogers@google.com>
 <20190621082422.GH3436@hirez.programming.kicks-ass.net>
 <CAP-5=fW7sMjQEHm+1e=cdAi+ZyP53UyU7xhAbnouMApuxYqrhw@mail.gmail.com>
 <20190624075520.GC3436@hirez.programming.kicks-ass.net>
 <CAP-5=fU=xbP39b6WZV4h92g6Ub_w4tH2JdApw5t6DTyZqxShUQ@mail.gmail.com>
 <CAKTKpr6m7YzqJ7U2icNHq7ZwoG0pw8ws_EHcLR+-T6ZeEfe15Q@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAKTKpr6m7YzqJ7U2icNHq7ZwoG0pw8ws_EHcLR+-T6ZeEfe15Q@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

On Fri, Aug 23, 2019 at 04:13:46PM +0530, Ganapatrao Kulkarni wrote:

> We are seeing regression with our uncore perf driver(Marvell's
> ThunderX2, ARM64 server platform) on 5.3-Rc1.
> After bisecting, it turned out to be this patch causing the issue.

Funnily enough; the email you replied to didn't contain a patch.

> Test case:
> Load module and run perf for more than 4 events( we have 4 counters,
> event multiplexing takes place for more than 4 events), then unload
> module.
> With this sequence of testing, the system hangs(soft lockup) after 2
> or 3 iterations. Same test runs for hours on 5.2.
> 
> while [ 1 ]
> do
>         rmmod thunderx2_pmu
>         modprobe thunderx2_pmu
>         perf stat -a -e \
>         uncore_dmc_0/cnt_cycles/,\
>         uncore_dmc_0/data_transfers/,\
>         uncore_dmc_0/read_txns/,\
>         uncore_dmc_0/config=0xE/,\
>         uncore_dmc_0/write_txns/ sleep 1
>         sleep 2
> done

Can you reproduce without the module load+unload? I don't think people
routinely unload modules.