netdev - Re: [PATCH net-next 3/5] net: mvpp2: cls: Use RSS contexts to handle RSS tables

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Date:   Sat, 9 May 2020 02:12:57 +0200
From:   Matteo Croce <mcroce@...hat.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     Maxime Chevallier <maxime.chevallier@...tlin.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        gregory.clement@...tlin.com, miquel.raynal@...tlin.com,
        Nadav Haklai <nadavh@...vell.com>,
        Stefan Chulski <stefanc@...vell.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>
Subject: Re: [PATCH net-next 3/5] net: mvpp2: cls: Use RSS contexts to handle
 RSS tables

On Thu, Apr 23, 2020 at 7:00 PM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> On Tue, Apr 14, 2020 at 01:43:02AM +0200, Matteo Croce wrote:
> > On Tue, Apr 14, 2020 at 1:21 AM Maxime Chevallier
> > <maxime.chevallier@...tlin.com> wrote:
> > >
> > > The PPv2 controller has 8 RSS tables that are shared across all ports on
> > > a given PPv2 instance. The previous implementation allocated one table
> > > per port, leaving others unused.
> > >
> > > By using RSS contexts, we can make use of multiple RSS tables per
> > > port, one being the default table (always id 0), the other ones being
> > > used as destinations for flow steering, in the same way as rx rings.
> > >
> > > This commit introduces RSS contexts management in the PPv2 driver. We
> > > always reserve one table per port, allocated when the port is probed.
> > >
> > > The global table list is stored in the struct mvpp2, as it's a global
> > > resource. Each port then maintains a list of indices in that global
> > > table, that way each port can have it's own numbering scheme starting
> > > from 0.
> > >
> > > One limitation that seems unavoidable is that the hashing parameters are
> > > shared across all RSS contexts for a given port. Hashing parameters for
> > > ctx 0 will be applied to all contexts.
> > >
> > > Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> >
> > Hi all,
> >
> > I noticed that enabling rxhash blocks the RX on my Macchiatobin. It
> > works fine with the 10G ports (the RX rate goes 4x up) but it
> > completely kills the gigabit interface.
> >
> > # 10G port
> > root@...chiatobin:~# iperf3 -c 192.168.0.2
> > Connecting to host 192.168.0.2, port 5201
> > [  5] local 192.168.0.1 port 42394 connected to 192.168.0.2 port 5201
> > [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
> > [  5]   0.00-1.00   sec   941 MBytes  7.89 Gbits/sec  4030    250 KBytes
> > [  5]   1.00-2.00   sec   933 MBytes  7.82 Gbits/sec  4393    240 KBytes
> > root@...chiatobin:~# ethtool -K eth0 rxhash on
> > root@...chiatobin:~# iperf3 -c 192.168.0.2
> > Connecting to host 192.168.0.2, port 5201
> > [  5] local 192.168.0.1 port 42398 connected to 192.168.0.2 port 5201
> > [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
> > [  5]   0.00-1.00   sec   860 MBytes  7.21 Gbits/sec  428    410 KBytes
> > [  5]   1.00-2.00   sec   859 MBytes  7.20 Gbits/sec  185    563 KBytes
> >
> > # gigabit port
> > root@...chiatobin:~# iperf3 -c turbo
> > Connecting to host turbo, port 5201
> > [  5] local 192.168.85.42 port 45144 connected to 192.168.85.6 port 5201
> > [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
> > [  5]   0.00-1.00   sec   113 MBytes   948 Mbits/sec    0    407 KBytes
> > [  5]   1.00-2.00   sec   112 MBytes   942 Mbits/sec    0    428 KBytes
> > root@...chiatobin:~# ethtool -K eth2 rxhash on
> > root@...chiatobin:~# iperf3 -c turbo
> > iperf3: error - unable to connect to server: Resource temporarily unavailable
> >
> > I've bisected and it seems that this commit causes the issue. I tried
> > to revert it on nex-next as a second test, but the code has changed a
> > lot much since, generating too much conflicts.
> > Can you have a look into this?
>
> This behaviour on eth2 is confirmed here on v5.6.  Turning on rxhash
> appears to prevent eth2 working.
>
> Maxime, please look into this regression, thanks.
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up
>

Hi,

What do you think about temporarily disabling it like this?

--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -5775,7 +5775,8 @@ static int mvpp2_port_probe(struct platform_device *pdev,
                            NETIF_F_HW_VLAN_CTAG_FILTER;

        if (mvpp22_rss_is_supported()) {
-               dev->hw_features |= NETIF_F_RXHASH;
+               if (port->phy_interface != PHY_INTERFACE_MODE_SGMII)
+                       dev->hw_features |= NETIF_F_RXHASH;
                dev->features |= NETIF_F_NTUPLE;
        }


David, is this "workaround" too bad to get accepted?

Bye,

--
Matteo Croce
per aspera ad upstream