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

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Message-ID: <20230614221807.akvkncurzh5qxjvi@mercury.elektranox.org>
Date:   Thu, 15 Jun 2023 00:18:07 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Vincent Legoll <vincent.legoll@...il.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 07:51:21PM +0000, Vincent Legoll wrote:
> 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 saw it multiple times (4 or 5) within a few tries (I guess around
20). I could see it with and without applying load on the memory.
Tests have been running globally for a second using 'sleep 1' (just
like the example from Sascha Hauer in the perf patch)

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

In my case it's Debian unstable.

-- Sebastian

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