netdev - Re: Bypass qdiscs?

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Date: Mon, 6 Nov 2023 11:17:38 -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 Mon, Nov 6, 2023 at 11:12 AM Jamal Hadi Salim <jhs@...atatu.com> wrote:
>
> 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.


BTW, Homa in-kernel instead of bypass is a better approach because you
get the advantages of all other infra that the kernel offers..

cheers,
jamal

> cheers,
> jamal
> >