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From: Tom Herbert <tom@herbertland.com>
To: Brenden Blanco <bblanco@plumgrid.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>,
	Martin KaFai Lau <kafai@fb.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Ari Saha <as754m@att.com>, Or Gerlitz <gerlitz.or@gmail.com>,
	john fastabend <john.fastabend@gmail.com>,
	Hannes Frederic Sowa <hannes@stressinduktion.org>,
	Thomas Graf <tgraf@suug.ch>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH v6 12/12] net/mlx4_en: add prefetch in xdp rx path
Date: Sun, 10 Jul 2016 15:50:10 -0500	[thread overview]
Message-ID: <CALx6S35rcgwZdYGp1fVDa4s_cvhX+B=d8HboAzFedELMH9Vzgw@mail.gmail.com> (raw)
In-Reply-To: <20160708164939.GA30632@gmail.com>

> This particular patch in the series is meant to be standalone exactly
> for this reason. I don't pretend to assert that this optimization will
> work for everybody, or even for a future version of me with different
> hardware. But, it passes my internal criteria for usefulness:
> 1. It provides a measurable gain in the experiments that I have at hand
> 2. The code is easy to review
> 3. The change does not negatively impact non-XDP users
>
> I would love to have a solution for all mlx4 driver users, but this
> patch set is focused on a different goal. So, without munging a
> different set of changes for the universal use case, and probably
> violating criteria #2 or #3, I went with what you see.
>
> In hopes of not derailing the whole patch series, what is an actionable
> next step for this patch #12?
> Ideas:
> Pick a safer N? (I saw improvements with N=1 as well)
> Drop this patch?
>
As Alexei mentioned the right prefetch model may be dependent on
workload. For instance, the XDP program for an ILA router is is far
less code path than packets going through TCP so it makes sense that
we would want different prefetch characteristics to optimize for each
case. Can we make this a configurable knob for each RX queue to allow
that?

> One thing I definitely don't want to do is go into the weeds trying to
> get a universal prefetch logic in order to merge the XDP framework, even
> though I agree the net result would benefit everybody.

Agreed, a salient point of XDP is that it's _not_ a generic mechanism
meant for all applications. We don't want to sacrifice performance for
generality.

Tom

  parent reply	other threads:[~2016-07-10 20:50 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-08  2:15 [PATCH v6 00/12] Add driver bpf hook for early packet drop and forwarding Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 01/12] bpf: add XDP prog type for early driver filter Brenden Blanco
2016-07-09  8:14   ` Jesper Dangaard Brouer
2016-07-09 13:47     ` Tom Herbert
2016-07-10 13:37       ` Jesper Dangaard Brouer
2016-07-10 17:09         ` Brenden Blanco
2016-07-10 20:30           ` Tom Herbert
2016-07-11 10:15             ` Daniel Borkmann
2016-07-11 12:58               ` Jesper Dangaard Brouer
2016-07-10 20:27         ` Tom Herbert
2016-07-11 11:36           ` Jesper Dangaard Brouer
2016-07-10 20:56   ` Tom Herbert
2016-07-11 16:51     ` Brenden Blanco
2016-07-11 21:21       ` Daniel Borkmann
2016-07-10 21:04   ` Tom Herbert
2016-07-11 13:53     ` Jesper Dangaard Brouer
2016-07-08  2:15 ` [PATCH v6 02/12] net: add ndo to set xdp prog in adapter rx Brenden Blanco
2016-07-10 20:59   ` Tom Herbert
2016-07-11 10:35     ` Daniel Borkmann
2016-07-08  2:15 ` [PATCH v6 03/12] rtnl: add option for setting link xdp prog Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 04/12] net/mlx4_en: add support for fast rx drop bpf program Brenden Blanco
2016-07-09 14:07   ` Or Gerlitz
2016-07-10 15:40     ` Brenden Blanco
2016-07-10 16:38       ` Tariq Toukan
2016-07-09 19:58   ` Saeed Mahameed
2016-07-09 21:37     ` Or Gerlitz
2016-07-10 15:25     ` Tariq Toukan
2016-07-10 16:05       ` Brenden Blanco
2016-07-11 11:48         ` Saeed Mahameed
2016-07-11 21:49           ` Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 05/12] Add sample for adding simple drop program to link Brenden Blanco
2016-07-09 20:21   ` Saeed Mahameed
2016-07-11 11:09   ` Jamal Hadi Salim
2016-07-11 13:37     ` Jesper Dangaard Brouer
2016-07-16 14:55       ` Jamal Hadi Salim
2016-07-08  2:15 ` [PATCH v6 06/12] net/mlx4_en: add page recycle to prepare rx ring for tx support Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 07/12] bpf: add XDP_TX xdp_action for direct forwarding Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 08/12] net/mlx4_en: break out tx_desc write into separate function Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 09/12] net/mlx4_en: add xdp forwarding and data write support Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 10/12] bpf: enable direct packet data write for xdp progs Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 11/12] bpf: add sample for xdp forwarding and rewrite Brenden Blanco
2016-07-08  2:15 ` [PATCH v6 12/12] net/mlx4_en: add prefetch in xdp rx path Brenden Blanco
2016-07-08  3:56   ` Eric Dumazet
2016-07-08  4:16     ` Alexei Starovoitov
2016-07-08  6:56       ` Eric Dumazet
2016-07-08 16:49         ` Brenden Blanco
2016-07-10 20:48           ` Tom Herbert
2016-07-10 20:50           ` Tom Herbert [this message]
2016-07-11 14:54             ` Jesper Dangaard Brouer
2016-07-08 15:20     ` Jesper Dangaard Brouer
2016-07-08 16:02       ` [net-next PATCH RFC] mlx4: RX prefetch loop Jesper Dangaard Brouer
2016-07-11 11:09         ` Jesper Dangaard Brouer
2016-07-11 16:00           ` Brenden Blanco
2016-07-11 23:05           ` Alexei Starovoitov
2016-07-12 12:45             ` Jesper Dangaard Brouer
2016-07-12 16:46               ` Alexander Duyck
2016-07-12 19:52                 ` Jesper Dangaard Brouer
2016-07-13  1:37                   ` Alexei Starovoitov
2016-07-10 16:14 ` [PATCH v6 00/12] Add driver bpf hook for early packet drop and forwarding Tariq Toukan

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