From: Andre Hedrick <andre@linux-ide.org>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: netdev@oss.sgi.com, linux-kernel@vger.kernel.org,
Werner Almesberger <werner@almesberger.net>,
Nivedita Singhvi <niv@us.ibm.com>
Subject: Re: TOE brain dump
Date: Wed, 6 Aug 2003 00:12:36 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.10.10308060009130.25045-100000@master.linux-ide.org> (raw)
In-Reply-To: <3F2CAE61.7070401@pobox.com>
Jeff,
Do be sure to check that your data payload is correct.
Everyone knows that a router/gateway/switch with a sticky bit in its
memory will recompute the net crc16 checksum insure it pass the to the nic
regardless. It is amazing how much data can be corrupted by a network
environment via all the NFS/NBD/etc wantabie storage products out there.
Just a chuckle for you to ponder.
--a
On Sun, 3 Aug 2003, Jeff Garzik wrote:
> Werner Almesberger wrote:
> > Jeff Garzik wrote:
> >
> >>jabbering at the same time. TCP is a "one size fits all" solution, but
> >>it doesn't work well for everyone.
> >
> >
> > But then, ten "optimized xxPs" that work well in two different
> > scenarios each, but not so good in the 98 others, wouldn't be
> > much fun either.
> >
> > It's been tried a number of times. Usually, real life sneaks
> > in at one point or another, leaving behind a complex mess.
> > When they've sorted out these problems, regular TCP has caught
> > up with the great optimized transport protocols. At that point,
> > they return to their niche, sometimes tail between legs and
> > muttering curses, sometimes shaking their fist and boldly
> > proclaiming how badly they'll rub TCP in the dirt in the next
> > round. Maybe they shed off some of the complexity, and trade it
> > for even more aggressive optimization, which puts them into
> > their niche even more firmly. Eventually, they fade away.
> >
> > There are cases where TCP doesn't work well, like a path of
> > badly mismatched link layers, but such paths don't treat any
> > protocol following the end-to-end principle kindly.
> >
> > Another problem of TCP is that it has grown a bit too many
> > knobs you need to turn before it works over your really fast
> > really long pipe. (In one of the OLS after dinner speeches,
> > this was quite appropriately called the "wizard gap".)
> >
> >
> >>It's obviously not over a WAN...
> >
> >
> > That's why NFS turned off UDP checksums ;-) As soon as you put
> > it on IP, it will crawl to distances you didn't imagine in your
> > wildest dreams. It always does.
>
> Really fast, really long pipes in practice don't exist for 99.9% of all
> Internet users.
>
>
> When you approach traffic levels that push you want to offload most of
> the TCP net stack, then TCP isn't the right solution for you anymore,
> all things considered.
>
>
> The Linux net stack just isn't built to be offloaded. TOE engines will
> either need to (1) fall back to Linux software for all-but-the-common
> case (otherwise netfilter, etc. break), or, (2) will need to be
> hideously complex beasts themselves. And I can't see ASIC and firmware
> designers being excited about implementing netfilter on a PCI card :)
>
> Unfortunately some vendors seem to choosing TOE option #3: TCP offload
> which introduces many limitations (connection limits, netfilter not
> supported, etc.) which Linux never had before. Vendors don't seem to
> realize TOE has real potential to damage the "good network neighbor"
> image the net stack has. The Linux net stack's behavior is known,
> documented, predictable. TOE changes all that.
>
> There is one interesting TOE solution, that I have yet to see created:
> run Linux on an embedded processor, on the NIC. This stripped-down
> Linux kernel would perform all the header parsing, checksumming, etc.
> into the NIC's local RAM. The Linux OS driver interface becomes a
> virtual interface with a large MTU, that communicates from host CPU to
> NIC across the PCI bus using jumbo-ethernet-like data frames.
> Management frames would control the ethernet interface on the other side
> of the PCI bus "tunnel".
>
>
> >>So, fix the other end of the pipeline too, otherwise this fast network
> >>stuff is flashly but pointless. If you want to serve up data from disk,
> >>then start creating PCI cards that have both Serial ATA and ethernet
> >>connectors on them :) Cut out the middleman of the host CPU and host
> >>memory bus instead of offloading portions of TCP that do not need to be
> >>offloaded.
> >
> >
> > That's a good point. A hierarchical memory structure can help
> > here. Moving one end closer to the hardware, and letting it
> > know (e.g. through sendfile) that also the other end is close
> > (or can be reached more directly that through some hopelessly
> > crowded main bus) may help too.
>
> Definitely.
>
> Jeff
>
>
>
> -
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next prev parent reply other threads:[~2003-08-06 7:23 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-02 17:04 TOE brain dump Werner Almesberger
2003-08-02 17:32 ` Nivedita Singhvi
2003-08-02 18:06 ` Werner Almesberger
2003-08-02 19:08 ` Jeff Garzik
2003-08-02 21:49 ` Werner Almesberger
2003-08-03 6:40 ` Jeff Garzik
2003-08-03 17:57 ` Werner Almesberger
2003-08-03 18:27 ` Erik Andersen
2003-08-03 19:40 ` Larry McVoy
2003-08-03 20:13 ` David Lang
2003-08-03 20:30 ` Larry McVoy
2003-08-03 21:21 ` David Lang
2003-08-03 23:44 ` Larry McVoy
2003-08-03 21:58 ` Jeff Garzik
2003-08-05 19:28 ` Timothy Miller
2003-08-03 20:34 ` jamal
2003-08-04 1:47 ` Glen Turner
2003-08-04 3:48 ` Larry McVoy
2003-08-06 7:12 ` Andre Hedrick [this message]
[not found] ` <Pine.LNX.4.10.10308060009130.25045-100000@master.linux-ide .org>
2003-08-06 8:20 ` Lincoln Dale
2003-08-06 8:22 ` David S. Miller
2003-08-06 13:07 ` Jesse Pollard
2003-08-03 19:21 ` Eric W. Biederman
2003-08-04 19:24 ` Werner Almesberger
2003-08-04 19:26 ` David S. Miller
2003-08-05 17:19 ` Eric W. Biederman
2003-08-06 5:13 ` Werner Almesberger
2003-08-06 7:58 ` Eric W. Biederman
2003-08-06 13:37 ` Werner Almesberger
2003-08-06 15:58 ` Andy Isaacson
2003-08-06 16:27 ` Chris Friesen
2003-08-06 17:01 ` Andy Isaacson
2003-08-06 17:55 ` Matti Aarnio
2003-08-07 2:14 ` Lincoln Dale
2003-08-06 12:46 ` Jesse Pollard
2003-08-06 16:25 ` Andy Isaacson
2003-08-06 18:58 ` Jesse Pollard
2003-08-06 19:39 ` Andy Isaacson
2003-08-06 21:13 ` David Schwartz
2003-08-03 4:01 ` Ben Greear
2003-08-03 6:22 ` Alan Shih
2003-08-03 6:41 ` Jeff Garzik
2003-08-03 8:25 ` David Lang
2003-08-03 18:05 ` Werner Almesberger
2003-08-03 22:02 ` Alan Shih
2003-08-03 20:52 ` Alan Cox
2003-08-04 14:36 ` Ingo Oeser
2003-08-04 17:19 ` Alan Shih
2003-08-05 8:15 ` Ingo Oeser
2003-08-02 20:57 ` Alan Cox
2003-08-02 22:14 ` Werner Almesberger
2003-08-03 20:51 ` Alan Cox
[not found] <g83n.8vu.9@gated-at.bofh.it>
2003-08-03 12:13 ` Ihar 'Philips' Filipau
2003-08-03 18:10 ` Werner Almesberger
2003-08-04 8:55 ` Ihar 'Philips' Filipau
2003-08-04 13:08 ` Jesse Pollard
2003-08-04 19:32 ` Werner Almesberger
2003-08-04 19:48 ` David Lang
2003-08-04 19:56 ` Werner Almesberger
2003-08-04 20:01 ` David Lang
2003-08-04 20:09 ` Werner Almesberger
2003-08-04 20:24 ` David Lang
2003-08-05 1:38 ` Werner Almesberger
2003-08-05 1:46 ` David Lang
2003-08-05 1:54 ` Larry McVoy
2003-08-05 2:30 ` Werner Almesberger
2003-08-06 1:47 ` Val Henson
2003-08-05 3:04 ` Werner Almesberger
2003-08-04 23:30 ` Peter Chubb
[not found] <gq0f.8bj.9@gated-at.bofh.it>
[not found] ` <gvCD.4mJ.5@gated-at.bofh.it>
[not found] ` <gJmp.7Th.33@gated-at.bofh.it>
[not found] ` <gNpS.2YJ.9@gated-at.bofh.it>
2003-08-04 14:15 ` Ihar 'Philips' Filipau
2003-08-04 14:56 ` Jesse Pollard
2003-08-04 15:51 ` Ihar 'Philips' Filipau
2003-08-04 18:36 Perez-Gonzalez, Inaky
2003-08-04 19:03 ` Alan Cox
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