linux-kernel - Re: [PATCH v5 00/25] Add perf support to the rockchip-dfi driver

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Date:   Wed, 14 Jun 2023 19:51:21 +0000
From:   Vincent Legoll <vincent.legoll@...il.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     Sascha Hauer <s.hauer@...gutronix.de>,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Heiko Stuebner <heiko@...ech.de>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>, kernel@...gutronix.de,
        Michael Riesch <michael.riesch@...fvision.net>,
        Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v5 00/25] Add perf support to the rockchip-dfi driver

Hi,

On Wed, Jun 14, 2023 at 3:27 PM Sebastian Reichel
<sebastian.reichel@...labora.com> wrote:
> On Wed, Jun 14, 2023 at 03:40:34PM +0200, Sebastian Reichel wrote:
> > I tested the series on RK3588 EVB1. The read/write byts looks
> > sensible. Sometimes cycles reads unrealistic values, though:
> >
> > 18446744070475110400      rockchip_ddr/cycles/
>
> I have seen this going off a few times with and without memory
> pressure. If it's way off, it always seems to follow the same
> pattern: The upper 32 bits are 0xffffffff instead of 0x00000000
> with the lower 32 bits containing sensible data.

How often is that happening ?

I have been running this in a loop with varying sleep duration for
the last few hours without hitting it, with and without memtester.

REPEATS=1000
MAX_DURATION=100

OUT="/tmp/perf-dfi-rk3588-${REPEATS}x${MAX_DURATION}s.txt"
echo -n > $OUT

for i in $(seq $REPEATS) ; do
  DURATION=$(shuf -i "0-${MAX_DURATION}" -n 1)
  echo -n "${DURATION} : " >> $OUT
  perf stat -a -e rockchip_ddr/cycles/ sleep $DURATION 2>&1 | awk
'/rockchip_ddr/ {printf("%X\n", int($1))}' >> $OUT
done

BTW, it's on a musl-libc arm64 void linux userspace.

-- 
Vincent Legoll