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

[Stefan Chulski]

> -----Original Message-----
> From: Matteo Croce <mcroce@xxxxxxxxxx>
> Sent: Saturday, May 9, 2020 3:13 AM
> To: David S . Miller <davem@xxxxxxxxxxxxx>
> Cc: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>; netdev
> <netdev@xxxxxxxxxxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>; Antoine
> Tenart <antoine.tenart@xxxxxxxxxxx>; Thomas Petazzoni
> <thomas.petazzoni@xxxxxxxxxxx>; gregory.clement@xxxxxxxxxxx;
> miquel.raynal@xxxxxxxxxxx; Nadav Haklai <nadavh@xxxxxxxxxxx>; Stefan
> Chulski <stefanc@xxxxxxxxxxx>; Marcin Wojtas <mw@xxxxxxxxxxxx>; Linux
> ARM <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Russell King - ARM Linux admin
> <linux@xxxxxxxxxxxxxxx>
> Subject: [EXT] Re: [PATCH net-next 3/5] net: mvpp2: cls: Use RSS contexts to
> handle RSS tables
> 
> External Email
> 
> ----------------------------------------------------------------------
> On Thu, Apr 23, 2020 at 7:00 PM Russell King - ARM Linux admin
> <linux@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > >
> > > 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@macchiatobin:~# 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@macchiatobin:~# ethtool -K eth0 rxhash on root@macchiatobin:~#
> > > 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@macchiatobin:~# 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@macchiatobin:~# ethtool -K eth2 rxhash on root@macchiatobin:~#
> > > 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://urldefense.proofpoint.com/v2/url?u=https-3A__www.armlinux.org.
> >
> uk_developer_patches_&d=DwIBaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=DDQ3dK
> wkTIxK
> > Al6_Bs7GMx4zhJArrXKN2mDMOXGh7lg&m=ntT7WKmzla65VWVPZMCr2-
> 8bTGq4cXdJ1RRL
> > gqFkmUc&s=jhKRohlyU0XtX0U0Rjt6XvJgMKLy_HedaFVSJwGYuD8&e=
> > 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?

Not sure that RSS related to physical interface(SGMII), better just remove NETIF_F_RXHASH as "workaround".

Stefan.