linux-kernel - Re: [RFC] [PATCH net-next v5 3/3] r8169: Implement dynamic ASPM mechanism

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Date:   Thu, 16 Sep 2021 12:12:32 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     hkallweit1@...il.com, nic_swsd@...ltek.com, bhelgaas@...gle.com,
        davem@...emloft.net, kuba@...nel.org, anthony.wong@...onical.com,
        netdev@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] [PATCH net-next v5 3/3] r8169: Implement dynamic ASPM
 mechanism

On Thu, Sep 16, 2021 at 11:44:17PM +0800, Kai-Heng Feng wrote:
> r8169 NICs on some platforms have abysmal speed when ASPM is enabled.
> Same issue can be observed with older vendor drivers.
> 
> The issue is however solved by the latest vendor driver. There's a new
> mechanism, which disables r8169's internal ASPM when the NIC traffic has
> more than 10 packets, and vice versa. 

Obviously this is a *rate*, not an absolute number.  I think you mean
something like "10 packets in 1000ms".

> The possible reason for this is
> likely because the buffer on the chip is too small for its ASPM exit
> latency.
> 
> Realtek confirmed that all their PCIe LAN NICs, r8106, r8168 and r8125
> use dynamic ASPM under Windows. So implement the same mechanism here to
> resolve the issue.
> 
> Also introduce a lock to prevent race on accessing config registers.

Can you please include the bugzilla link where you attached lspci
data?  I think it's this:

  https://bugzilla.kernel.org/show_bug.cgi?id=214307

> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>