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Message-ID: <DB8PR04MB6795DD09B08C29C89C418E4EE62C9@DB8PR04MB6795.eurprd04.prod.outlook.com>
Date: Tue, 18 May 2021 12:35:49 +0000
From: Joakim Zhang <qiangqing.zhang@....com>
To: Dave Taht <dave.taht@...il.com>
CC: Frieder Schrempf <frieder.schrempf@...tron.de>,
dl-linux-imx <linux-imx@....com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: RE: i.MX8MM Ethernet TX Bandwidth Fluctuations
Hi Dave,
> -----Original Message-----
> From: Dave Taht <dave.taht@...il.com>
> Sent: 2021年5月17日 20:48
> To: Joakim Zhang <qiangqing.zhang@....com>
> Cc: Frieder Schrempf <frieder.schrempf@...tron.de>; dl-linux-imx
> <linux-imx@....com>; netdev@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org
> Subject: Re: i.MX8MM Ethernet TX Bandwidth Fluctuations
>
> On Mon, May 17, 2021 at 3:25 AM Joakim Zhang <qiangqing.zhang@....com>
> wrote:
> >
> >
> > Hi Frieder,
> >
> > > -----Original Message-----
> > > From: Frieder Schrempf <frieder.schrempf@...tron.de>
> > > Sent: 2021年5月17日 15:17
> > > To: Joakim Zhang <qiangqing.zhang@....com>; dl-linux-imx
> > > <linux-imx@....com>; netdev@...r.kernel.org;
> > > linux-arm-kernel@...ts.infradead.org
> > > Subject: Re: i.MX8MM Ethernet TX Bandwidth Fluctuations
> > >
> > > Hi Joakim,
> > >
> > > On 13.05.21 14:36, Joakim Zhang wrote:
> > > >
> > > > Hi Frieder,
> > > >
> > > > For NXP release kernel, I tested on i.MX8MQ/MM/MP, I can reproduce
> > > > on
> > > L5.10, and can't reproduce on L5.4.
> > > > According to your description, you can reproduce this issue both
> > > > L5.4 and
> > > L5.10? So I need confirm with you.
> > >
> > > Thanks for looking into this. I could reproduce this on 5.4 and 5.10
> > > but both kernels were official mainline kernels and **not** from the
> > > linux-imx downstream tree.
> > Ok.
> >
> > > Maybe there is some problem in the mainline tree and it got included
> > > in the NXP release kernel starting from L5.10?
> > No, this much looks like a known issue, it should always exist after adding
> AVB support in mainline.
> >
> > ENET IP is not a _real_ multiple queues per my understanding, queue 0 is for
> best effort. And the queue 1&2 is for AVB stream whose default bandwidth
> fraction is 0.5 in driver. (i.e. 50Mbps for 100Mbps and 500Mbps for 1Gbps).
> When transmitting packets, net core will select queues randomly, which
> caused the tx bandwidth fluctuations. So you can change to use single queue if
> you care more about tx bandwidth. Or you can refer to NXP internal
> implementation.
> > e.g.
> > --- a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > @@ -916,8 +916,8 @@
> > <&clk
> IMX8MQ_CLK_ENET_PHY_REF>;
> > clock-names = "ipg", "ahb", "ptp",
> > "enet_clk_ref",
> "enet_out";
> > - fsl,num-tx-queues = <3>;
> > - fsl,num-rx-queues = <3>;
> > + fsl,num-tx-queues = <1>;
> > + fsl,num-rx-queues = <1>;
> > status = "disabled";
> > };
> > };
> >
> > I hope this can help you :)
>
> Patching out the queues is probably not the right thing.
>
> for starters... Is there BQL support in this driver? It would be helpful to have on
> all queues.
There is no BQL support in this driver, and BQL may improve throughput further, but should not be the root cause of this reported issue.
> Also if there was a way to present it as two interfaces, rather than one, that
> would allow for a specific avb device to be presented.
>
> Or:
>
> Is there a standard means of signalling down the stack via the IP layer (a dscp?
> a setsockopt?) that the AVB queue is requested?
>
AFAIK, AVB is scope of VLAN, so we can queue AVB packets into queue 1&2 based on VLAN-ID.
Best Regards,
Joakim Zhang
> > Best Regards,
> > Joakim Zhang
> > > Best regards
> > > Frieder
> > >
> > > >
> > > > Best Regards,
> > > > Joakim Zhang
> > > >
> > > >> -----Original Message-----
> > > >> From: Joakim Zhang <qiangqing.zhang@....com>
> > > >> Sent: 2021年5月12日 19:59
> > > >> To: Frieder Schrempf <frieder.schrempf@...tron.de>; dl-linux-imx
> > > >> <linux-imx@....com>; netdev@...r.kernel.org;
> > > >> linux-arm-kernel@...ts.infradead.org
> > > >> Subject: RE: i.MX8MM Ethernet TX Bandwidth Fluctuations
> > > >>
> > > >>
> > > >> Hi Frieder,
> > > >>
> > > >> Sorry, I missed this mail before, I can reproduce this issue at
> > > >> my side, I will try my best to look into this issue.
> > > >>
> > > >> Best Regards,
> > > >> Joakim Zhang
> > > >>
> > > >>> -----Original Message-----
> > > >>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
> > > >>> Sent: 2021年5月6日 22:46
> > > >>> To: dl-linux-imx <linux-imx@....com>; netdev@...r.kernel.org;
> > > >>> linux-arm-kernel@...ts.infradead.org
> > > >>> Subject: i.MX8MM Ethernet TX Bandwidth Fluctuations
> > > >>>
> > > >>> Hi,
> > > >>>
> > > >>> we observed some weird phenomenon with the Ethernet on our
> > > >>> i.MX8M-Mini boards. It happens quite often that the measured
> > > >>> bandwidth in TX direction drops from its expected/nominal value
> > > >>> to something like 50% (for 100M) or ~67% (for 1G) connections.
> > > >>>
> > > >>> So far we reproduced this with two different hardware designs
> > > >>> using two different PHYs (RGMII VSC8531 and RMII KSZ8081), two
> > > >>> different kernel versions (v5.4 and v5.10) and link speeds of 100M and
> 1G.
> > > >>>
> > > >>> To measure the throughput we simply run iperf3 on the target
> > > >>> (with a short p2p connection to the host PC) like this:
> > > >>>
> > > >>> iperf3 -c 192.168.1.10 --bidir
> > > >>>
> > > >>> But even something more simple like this can be used to get the
> > > >>> info (with 'nc -l -p 1122 > /dev/null' running on the host):
> > > >>>
> > > >>> dd if=/dev/zero bs=10M count=1 | nc 192.168.1.10 1122
> > > >>>
> > > >>> The results fluctuate between each test run and are sometimes 'good'
> > > (e.g.
> > > >>> ~90 MBit/s for 100M link) and sometimes 'bad' (e.g. ~45 MBit/s
> > > >>> for 100M
> > > >> link).
> > > >>> There is nothing else running on the system in parallel. Some
> > > >>> more info is also available in this post: [1].
> > > >>>
> > > >>> If there's anyone around who has an idea on what might be the
> > > >>> reason for this, please let me know!
> > > >>> Or maybe someone would be willing to do a quick test on his own
> > > hardware.
> > > >>> That would also be highly appreciated!
> > > >>>
> > > >>> Thanks and best regards
> > > >>> Frieder
> > > >>>
> > > >>> [1]:
> > > >>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%
> > > >>> 2Fco
> > > >>> mm
> > > >>> u
> > > >>>
> > > >>
> > >
> nity.nxp.com%2Ft5%2Fi-MX-Processors%2Fi-MX8MM-Ethernet-TX-Bandwidth-
> > > >>>
> > > >>
> > >
> Fluctuations%2Fm-p%2F1242467%23M170563&data=04%7C01%7Cqiang
> > > >>>
> > > >>
> > >
> qing.zhang%40nxp.com%7C5d4866d4565e4cbc36a008d9109da0ff%7C686ea1d
> > > >>>
> > > >>
> > >
> 3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637559091463792932%7CUnkno
> > > >>>
> > > >>
> > >
> wn%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1ha
> > > >>>
> > > >>
> > >
> WwiLCJXVCI6Mn0%3D%7C1000&sdata=ygcThQOLIzp0lzhXacRLjSjnjm1FEj
> > > >>> YSxakXwZtxde8%3D&reserved=0
>
>
>
> --
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> db04c41799908d91932059b%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%
> 7C0%7C637568524896127548%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4w
> LjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&am
> p;sdata=IPW1MPLSnitX0HUttdLtZysknzokRN5fYVPXrbJQhaY%3D&reserve
> d=0
>
> Dave Täht CTO, TekLibre, LLC
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