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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Date:   Thu, 19 Aug 2021 14:19:07 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     nic_swsd <nic_swsd@...ltek.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        LKML <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 Thu, Aug 19, 2021 at 2:08 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>
> 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?

It means what patch 1/3 fixes...

> 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.

OK. We can know if the 1 sec interval is enough once it's deployed in the wild.

>
> > 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.

Noted. Will annotate in next version.

Kai-Heng