From: Andrew Lunn <andrew@lunn.ch>
To: David Laight <David.Laight@aculab.com>
Cc: 'Richard Weinberger' <richard@nod.at>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"wei.fang@nxp.com" <wei.fang@nxp.com>,
"shenwei.wang@nxp.com" <shenwei.wang@nxp.com>,
"xiaoning.wang@nxp.com" <xiaoning.wang@nxp.com>,
"linux-imx@nxp.com" <linux-imx@nxp.com>
Subject: Re: high latency with imx8mm compared to imx6q
Date: Sat, 18 Feb 2023 02:04:35 +0100 [thread overview]
Message-ID: <Y/AkI7DUYKbToEpj@lunn.ch> (raw)
In-Reply-To: <b4fc00958e0249208b5aceecfa527161@AcuMS.aculab.com>
On Fri, Feb 17, 2023 at 08:49:23PM +0000, David Laight wrote:
> From: Richard Weinberger
> > Sent: 17 February 2023 16:53
> ...
> > I'm investigating into latency issues on an imx8mm system after
> > migrating from imx6q.
> > A regression test showed massive latency increases when single/small packets
> > are exchanged.
> >
> > A simple test using ping exhibits the problem.
> > Pinging the very same host from the imx8mm has a way higher RTT than from the imx6.
> >
> > Ping, 100 packets each, from imx6q:
> > rtt min/avg/max/mdev = 0.689/0.851/1.027/0.088 ms
> >
> > Ping, 100 packets each, from imx8mm:
> > rtt min/avg/max/mdev = 1.073/2.064/2.189/0.330 ms
> >
> > You can see that the average RTT has more than doubled.
> ...
>
> Is it just interrupt latency caused by interrupt coalescing
> to avoid excessive interrupts?
Just adding to this, it appears imx6q does not have support for
changing the interrupt coalescing. imx8m does appear to support it. So
try playing with ethtool -c/-C.
Andrew
next prev parent reply other threads:[~2023-02-18 1:04 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-17 16:52 fec: high latency with imx8mm compared to imx6q Richard Weinberger
2023-02-17 20:49 ` David Laight
2023-02-18 1:04 ` Andrew Lunn [this message]
2023-02-18 1:27 ` Wei Fang
2023-02-18 9:42 ` Richard Weinberger
2023-02-18 11:52 ` Wei Fang
2023-02-18 12:03 ` Richard Weinberger
2023-02-18 12:28 ` Wei Fang
2023-02-18 12:29 ` Wei Fang
2023-02-18 13:20 ` Richard Weinberger
2023-02-20 0:11 ` Andrew Lunn
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