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

From: Kai-Heng Feng <kai.heng.feng@canonical.com>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: nic_swsd <nic_swsd@realtek.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	David Miller <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Linux Netdev List <netdev@vger.kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next v3 0/3] r8169: Implement dynamic ASPM mechanism for recent 1.0/2.5Gbps Realtek NICs
Date: Thu, 19 Aug 2021 14:19:07 +0800	[thread overview]
Message-ID: <CAAd53p5Fu+x9M0fAta4k-8mja4Bxybhcg9veut4v7TVFZrD_aQ@mail.gmail.com> (raw)
In-Reply-To: <b14bc147-d39c-6f55-cc0e-7b2de92d23b1@gmail.com>

On Thu, Aug 19, 2021 at 2:08 PM Heiner Kallweit <hkallweit1@gmail.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