From: Magnus Karlsson <magnus.karlsson@gmail.com>
To: Dan Siemon <dan@coverfire.com>
Cc: Xdp <xdp-newbies@vger.kernel.org>
Subject: Re: AF_XDP Rx and overload
Date: Mon, 3 May 2021 10:31:10 +0200 [thread overview]
Message-ID: <CAJ8uoz3vFize=OW6HhFvMMVabsdioywUSC09sTz4mSOmnjT-0Q@mail.gmail.com> (raw)
In-Reply-To: <0b0ebcc691f6dfeb560c2faf1e329e059cbecc2d.camel@coverfire.com>
On Fri, Apr 30, 2021 at 7:24 PM Dan Siemon <dan@coverfire.com> wrote:
>
> When an AF_XDP based application is overloaded, it is preferable for
> the application to:
> * Service the Rx ring as fast as it can and drop in the application if
> required?
> * Let the Rx ring fill up and let the NIC drop?
Let the NIC drop, since this is much faster. And always process Tx
first, if you have such a component. This alleviates buffering
problems and makes sure you get as much as possible out of the system
to the devices that want your packets. You generally want to get as
many packets through your whole processing pipeline, not trying to
receive as many packets as possible (and not getting them the whole
way through).
>
> This is mostly a performance/PPS question. Obviously the application
> loses the ability to directly count the drops if the NIC drops among
> other limitations.
You will not be able to keep up counting anyway :-). It is not
possible to count all drops in user-space (or the kernel). You would
need HW support for this. Just think of blasting 162 Mpps at one port
and trying to count the drops in the CPU. Would need a lot of cores
for just that.
> If it makes a difference, the use case is only i40e right now.
>
prev parent reply other threads:[~2021-05-03 8:31 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 17:24 AF_XDP Rx and overload Dan Siemon
2021-05-03 8:31 ` Magnus Karlsson [this message]
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