netdev - Re: Bypass qdiscs?

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Message-ID: <CAM0EoMm+x2eOVbn_NMDYVu4tEjccvvHObt0OSPvCibMAfiNs5w@mail.gmail.com>
Date: Mon, 6 Nov 2023 11:12:48 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: David Ahern <dsahern@...nel.org>
Cc: Stephen Hemminger <stephen@...workplumber.org>, John Ousterhout <ouster@...stanford.edu>, 
	Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org
Subject: Re: Bypass qdiscs?

On Sun, Nov 5, 2023 at 11:27 PM David Ahern <dsahern@...nel.org> wrote:
>
> On 11/5/23 8:23 PM, Stephen Hemminger wrote:
> > On Sat, 4 Nov 2023 19:47:30 -0700
> > John Ousterhout <ouster@...stanford.edu> wrote:
> >
> >> I haven't tried creating a "pass through" qdisc, but that seems like a
> >> reasonable approach if (as it seems) there isn't something already
> >> built-in that provides equivalent functionality.
> >>
> >> -John-
> >>
> >> P.S. If hardware starts supporting Homa, I hope that it will be
> >> possible to move the entire transport to the NIC, so that applications
> >> can bypass the kernel entirely, as with RDMA.
> >
> > One old trick was setting netdev queue length to 0 to avoid qdisc.
> >
>
> tc qdisc replace dev <name> root noqueue
>
> should work

John,
IIUC,  Homa transmit is done by  a pacer that ensures the packets are
scheduled without forming the queues in the NIC. So what David said
above should be sufficient setup.

cheers,
jamal
>