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From: Bjorn Helgaas <email@example.com>
To: Kai-Heng Feng <firstname.lastname@example.org>
Cc: Heiner Kallweit <email@example.com>,
Bjorn Helgaas <firstname.lastname@example.org>,
David Miller <email@example.com>,
Jakub Kicinski <firstname.lastname@example.org>,
Anthony Wong <email@example.com>,
Linux Netdev List <firstname.lastname@example.org>,
Linux PCI <email@example.com>,
Subject: Re: [RFC] [PATCH net-next v5 0/3] r8169: Implement dynamic ASPM mechanism for recent 1.0/2.5Gbps Realtek NICs
Date: Fri, 8 Oct 2021 08:56:55 -0500 [thread overview]
Message-ID: <20211008135655.GA1326714@bhelgaas> (raw)
On Fri, Oct 01, 2021 at 12:17:26PM +0800, Kai-Heng Feng wrote:
> On Sat, Sep 18, 2021 at 6:09 AM Bjorn Helgaas <firstname.lastname@example.org> wrote:
> > On Thu, Sep 16, 2021 at 11:44:14PM +0800, Kai-Heng Feng wrote:
> > > The purpose of the series is to get comments and reviews so we can merge
> > > and test the series in downstream kernel.
> > >
> > > The latest Realtek vendor driver and its Windows driver implements a
> > > feature called "dynamic ASPM" which can improve performance on it's
> > > ethernet NICs.
> > >
> > > Heiner Kallweit pointed out the potential root cause can be that the
> > > buffer is too small for its ASPM exit latency.
> > I looked at the lspci data in your bugzilla
> > (https://bugzilla.kernel.org/show_bug.cgi?id=214307).
> > L1.2 is enabled, which requires the Latency Tolerance Reporting
> > capability, which helps determine when the Link will be put in L1.2.
> > IIUC, these are analogous to the DevCap "Acceptable Latency" values.
> > Zero latency values indicate the device will be impacted by any delay
> > (PCIe r5.0, sec 6.18).
> > Linux does not currently program those values, so the values there
> > must have been set by the BIOS. On the working AMD system, they're
> > set to 1048576ns, while on the broken Intel system, they're set to
> > 3145728ns.
> > I don't really understand how these values should be computed, and I
> > think they depend on some electrical characteristics of the Link, so
> > I'm not sure it's *necessarily* a problem that they are different.
> > But a 3X difference does seem pretty large.
> > So I'm curious whether this is related to the problem. Here are some
> > things we could try on the broken Intel system:
> Original network speed, tested via iperf3:
> TX: ~255 Mbps
> RX: ~490 Mbps
> > - What happens if you disable ASPM L1.2 using
> > /sys/devices/pci*/.../link/l1_2_aspm?
> TX: ~670 Mbps
> RX: ~670 Mbps
Do you remember if there were any dropped packets here? You mentioned
at  that you have also seen reports of issues with L0s and L1.1.
If you disable L1.2, L0s and L1.1 *should* still be enabled.
prev parent reply other threads:[~2021-10-08 13:57 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-16 15:44 Kai-Heng Feng
2021-09-16 15:44 ` [RFC] [PATCH net-next v5 1/3] PCI/ASPM: Introduce a new helper to report ASPM capability Kai-Heng Feng
2021-09-16 15:44 ` [RFC] [PATCH net-next v5 2/3] r8169: Use PCIe ASPM status for NIC ASPM enablement Kai-Heng Feng
2021-09-16 17:07 ` Bjorn Helgaas
2021-09-17 4:09 ` Kai-Heng Feng
2021-09-17 15:26 ` Bjorn Helgaas
2021-10-01 4:32 ` Kai-Heng Feng
2021-09-16 15:44 ` [RFC] [PATCH net-next v5 3/3] r8169: Implement dynamic ASPM mechanism Kai-Heng Feng
2021-09-16 17:12 ` Bjorn Helgaas
2021-09-17 4:19 ` Kai-Heng Feng
2021-09-17 22:09 ` [RFC] [PATCH net-next v5 0/3] r8169: Implement dynamic ASPM mechanism for recent 1.0/2.5Gbps Realtek NICs Bjorn Helgaas
2021-10-01 4:17 ` Kai-Heng Feng
2021-10-07 19:10 ` Bjorn Helgaas
2021-10-08 13:56 ` Bjorn Helgaas [this message]
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