linux-kernel - Re: [PATCH net-next v3 0/3] r8169: Implement dynamic ASPM mechanism for recent 1.0/2.5Gbps Realtek NICs

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Message-ID: <b14bc147-d39c-6f55-cc0e-7b2de92d23b1@gmail.com>
Date:   Thu, 19 Aug 2021 08:08:10 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>, nic_swsd@...ltek.com,
        bhelgaas@...gle.com
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 0/3] r8169: Implement dynamic ASPM mechanism
 for recent 1.0/2.5Gbps Realtek NICs

On 19.08.2021 07:45, Kai-Heng Feng wrote:
> The latest Realtek vendor driver and its Windows driver implements a
> feature called "dynamic ASPM" which can improve performance on it's
> ethernet NICs.
> 
This statement would need a proof. Which performance improvement
did you measure? And why should performance improve?
On mainline ASPM is disabled, therefore I don't think we can see
a performance improvement. More the opposite in the scenario
I described: If traffic starts and there's a congestion in the chip,
then it may take a second until ASPM gets disabled. This may hit
performance.

> Heiner Kallweit pointed out the potential root cause can be that the
> buffer is to small for its ASPM exit latency.
> 
> So bring the dynamic ASPM to r8169 so we can have both nice performance
> and powersaving at the same time.
> 
> v2:
> https://lore.kernel.org/netdev/20210812155341.817031-1-kai.heng.feng@canonical.com/
> 
> v1:
> https://lore.kernel.org/netdev/20210803152823.515849-1-kai.heng.feng@canonical.com/
> 
> Kai-Heng Feng (3):
>   r8169: Implement dynamic ASPM mechanism
>   PCI/ASPM: Introduce a new helper to report ASPM support status
>   r8169: Enable ASPM for selected NICs
> 
>  drivers/net/ethernet/realtek/r8169_main.c | 69 ++++++++++++++++++++---
>  drivers/pci/pcie/aspm.c                   | 11 ++++
>  include/linux/pci.h                       |  2 +
>  3 files changed, 74 insertions(+), 8 deletions(-)
> 
This series is meant for your downstream kernel only, and posted here to
get feedback. Therefore it should be annotated as RFC, not that it gets
applied accidentally.