netdev - Re: [Intel-wired-lan] NAT performance issue 944mbit -> ~40mbit

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Date:   Fri, 24 Jul 2020 14:33:33 +0200
From:   Ian Kumlien <ian.kumlien@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [Intel-wired-lan] NAT performance issue 944mbit -> ~40mbit

On Fri, Jul 24, 2020 at 2:01 PM Ian Kumlien <ian.kumlien@...il.com> wrote:
>
> On Fri, Jul 17, 2020 at 3:45 PM Ian Kumlien <ian.kumlien@...il.com> wrote:

[--8<--]

> As a side note, would something like this fix it - not even compile tested
>
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index 8bb3db2cbd41..1a7240aae85c 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -3396,6 +3396,13 @@ static int igb_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>                           "Width x2" :
>                           (hw->bus.width == e1000_bus_width_pcie_x1) ?
>                           "Width x1" : "unknown"), netdev->dev_addr);
> +               /* quirk */
> +#ifdef CONFIG_PCIEASPM
> +               if (hw->bus.width == e1000_bus_width_pcie_x1) {
> +                       /* single lane pcie causes problems with ASPM */
> +                       pdev->pcie_link_state->aspm_enabled = 0;
> +               }
> +#endif
>         }
>
>         if ((hw->mac.type >= e1000_i210 ||
>
> I don't know where the right place to put a quirk would be...

Ok so that was a real brainfart... turns out that there is a lack of
good ways to get to that but it was more intended to
know where the quirk should go...

Due to the lack of api:s i started wondering if this will apply to
more devices than just network cards - potentially we could
be a little bit more selective and only not enable it in one direction but...

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index b17e5ffd31b1..96a3c6837124 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -584,15 +584,16 @@ static void pcie_aspm_cap_init(struct
pcie_link_state *link, int blacklist)
         * given link unless components on both sides of the link each
         * support L0s.
         */
-       if (dwreg.support & upreg.support & PCIE_LINK_STATE_L0S)
-               link->aspm_support |= ASPM_STATE_L0S;
-       if (dwreg.enabled & PCIE_LINK_STATE_L0S)
-               link->aspm_enabled |= ASPM_STATE_L0S_UP;
-       if (upreg.enabled & PCIE_LINK_STATE_L0S)
-               link->aspm_enabled |= ASPM_STATE_L0S_DW;
-       link->latency_up.l0s = calc_l0s_latency(upreg.latency_encoding_l0s);
-       link->latency_dw.l0s = calc_l0s_latency(dwreg.latency_encoding_l0s);
-
+       if (pcie_get_width_cap(child) != PCIE_LNK_X1) {
+               if (dwreg.support & upreg.support & PCIE_LINK_STATE_L0S)
+                       link->aspm_support |= ASPM_STATE_L0S;
+               if (dwreg.enabled & PCIE_LINK_STATE_L0S)
+                       link->aspm_enabled |= ASPM_STATE_L0S_UP;
+               if (upreg.enabled & PCIE_LINK_STATE_L0S)
+                       link->aspm_enabled |= ASPM_STATE_L0S_DW;
+               link->latency_up.l0s =
calc_l0s_latency(upreg.latency_encoding_l0s);
+               link->latency_dw.l0s =
calc_l0s_latency(dwreg.latency_encoding_l0s);
+       }

this time it's compile tested...

It could also be  if (pcie_get_width_cap(child) > PCIE_LNK_X1) {

I assume that ASPM is not enabled for: PCIE_LNK_WIDTH_RESRV ;)