netdev - Re: Per-queue XDP programs, thoughts

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Message-ID: <20190416142811.3b3e3c16@cakuba.netronome.com>
Date:   Tue, 16 Apr 2019 14:28:11 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        ilias.apalodimas@...aro.org, toke@...hat.com,
        magnus.karlsson@...el.com, maciej.fijalkowski@...el.com,
        Jason Wang <jasowang@...hat.com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        David Miller <davem@...emloft.net>,
        Andy Gospodarek <andy@...yhouse.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        bpf@...r.kernel.org, Thomas Graf <tgraf@...g.ch>,
        Thomas Monjalon <thomas@...jalon.net>,
        Jonathan Lemon <jonathan.lemon@...il.com>
Subject: Re: Per-queue XDP programs, thoughts

On Tue, 16 Apr 2019 15:55:23 +0200, Jesper Dangaard Brouer wrote:
> On Mon, 15 Apr 2019 15:49:32 -0700
> Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:
> 
> > On Mon, 15 Apr 2019 18:32:58 +0200, Jesper Dangaard Brouer wrote:  
> > > On Mon, 15 Apr 2019 13:59:03 +0200 Björn Töpel <bjorn.topel@...el.com> wrote:    
> > > > Hi,
> > > > 
> > > > As you probably can derive from the amount of time this is taking, I'm
> > > > not really satisfied with the design of per-queue XDP program. (That,
> > > > plus I'm a terribly slow hacker... ;-)) I'll try to expand my thinking
> > > > in this mail!    
> > 
> > Jesper was advocating per-queue progs since very early days of XDP.
> > If it was easy to implement cleanly we would've already gotten it ;)  
> 
> (I cannot help to feel offended here...  IMHO that statement is BS,
> that is not how upstream development work, and sure, I am to blame as
> I've simply been to lazy or busy with other stuff to implement it.

Sincere apologies, definitely not what I was trying to say.

> It is not that hard to send down a queue# together with the XDP attach
> command.) 

That part is not hard, agreed.

> I've been advocating for per-queue progs from day-1, since this is an
> obvious performance advantage, given the programmer can specialize the
> BPF/XDP-prog to the filtered traffic.  I hope/assume we are on the same
> pages here, that per-queue progs is a performance optimization.
> 
> I guess the rest of the discussion in this thread is (1) if we can
> convince each-other that someone will actually use this optimization,
> and (2) if we can abstract this away from the user.

Yes, agreed.