linux-kernel - Re: [Resend PATCH] topology: Set capacity_freq

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Message-ID: <75f0bfc7-fb95-409a-a5d9-b00732e892f0@bp.renesas.com>
Date: Tue, 23 Jan 2024 16:23:51 +0000
From: Paul Barker <paul.barker.ct@...renesas.com>
To: Vincent Guittot <vincent.guittot@...aro.org>, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, dietmar.eggemann@....com,
 rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
 bristot@...hat.com, vschneid@...hat.com, sudeep.holla@....com,
 gregkh@...uxfoundation.org, rafael@...nel.org, linux-kernel@...r.kernel.org
Cc: lukasz.luba@....com, ionela.voinescu@....com
Subject: Re: [Resend PATCH] topology: Set capacity_freq_ref in all cases

On 17/01/2024 19:05, Vincent Guittot wrote:
> If "capacity-dmips-mhz" is not set, raw_capacity is null and we skip the
> normalization step which includes setting per_cpu capacity_freq_ref.
> Always register the notifier but skip the capacity normalization if
> raw_capacity is null.
> 
> Fixes: 9942cb22ea45 ("sched/topology: Add a new arch_scale_freq_ref() method")
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>

We've had some Ethernet performance issues with linux-next and v6.8-rc1
on the Renesas RZ/G2L and RZ/G2UL arm64 SoCs. I've confirmed that the
CPU frequency is stuck at the minimum (150MHz) in v6.8-rc1, even when
running iperf3. Applying this patch allows the SoC to switch up the the
maximum frequency (1200MHz) when needed and fixes our Ethernet
performance.

iperf3 results in Mbps for RZ/G2L SMARC evaluation board:
                TCP TX    TCP RX    UDP TX    UDP RX
v6.8-rc1        255       175       102       (*)
+this patch     874       650       802       948

(*) Testing UDP RX in v6.8-rc1 with a server sending traffic at 1Gbps
locks up our NFS rootfs mount so we don't get any result at all.

Results with v6.8-rc1 + this patch are in line with what we see in v6.7.

Tested-by: Paul Barker <paul.barker.ct@...renesas.com>
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