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Old 08-04-2010, 03:33 PM
Uwe Zimmermann
 
Default Fedora 13 networking performs extremely well

Hello,

our product "MIMIC Simulator" has been running on Fedora for a long time
(eg. see

http://www.gambitcomm.com/site/support/support_platforms.shtml

). But, we have seen a steady decline in performance over successive
versions of Fedora (eg. see

http://gambitcomm.blogspot.com/2010/06/mimic-1030-performance-test-report-high.html

Our application is somewhat unique in that it can create many (10s of
thousands) IP aliases, opens sockets to multiple ports on each.

Only with Fedora 13 (kernel version 2.6.33.6-147.fc13.x86_64) have we
seen a surprising performance improvement, where running 20,000 simulated
agents is the same as running 10, in terms of networking performance. At
first we could not believe it, but subsequent tests have confirmed that
we indeed are seeing the improved performance. The specific improvement
seems to be that the kernel seems to be efficiently demultiplexing among
all open sockets to deliver received messages from the network card.

Can some expert point me at a specific fix (spec, kernel module, source
code revision) that could account for this? It would be in the networking
code, possibly the socket demultiplexer. I have looked for this for a
while and just cannot find it. This change would be after Fedora 12.
Any hint would be appreciated.

Thank you in advance.

Uwe Zimmermann
Gambit Communications

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Old 08-09-2010, 06:31 PM
Uwe Zimmermann
 
Default Fedora 13 networking performs extremely well

No reply for 5 days, so I'll modify my question:

can someone point me in the direction of the experts, eg. mailing list,
name(s), organization, anything that might give me the answer?

Thanks a lot.

Uwe

On Wed, Aug 04, 2010 at 11:33:16AM -0400, Uwe Zimmermann wrote:
> ...

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Old 08-09-2010, 06:38 PM
Robert Myers
 
Default Fedora 13 networking performs extremely well

On Mon, Aug 9, 2010 at 2:31 PM, Uwe Zimmermann <uwe@gambitcomm.com> wrote:
>
> No reply for 5 days, so I'll modify my question:
>
> can someone point me in the direction of the experts, eg. *mailing list,
> name(s), organization, anything that might give me the answer?
>
> Thanks a lot.
>

How about Googling fedora+networking+consultants? 152,000 hits.

Robert
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Old 08-09-2010, 08:01 PM
 
Default Fedora 13 networking performs extremely well

Uwe Zimmermann <uwe@gambitcomm.com> writes:
> No reply for 5 days, so I'll modify my question:
>
> can someone point me in the direction of the experts, eg. mailing list,
> name(s), organization, anything that might give me the answer?

Why not track down where the kernel hackers hang out and ask them?
Maybe the appropirate bits went from linked lists to hash tables?

-wolfgang
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Old 08-18-2010, 08:57 PM
Bruno Wolff III
 
Default Fedora 13 networking performs extremely well

On Wed, Aug 04, 2010 at 11:33:16 -0400,
Uwe Zimmermann <uwe@gambitcomm.com> wrote:
>
> Can some expert point me at a specific fix (spec, kernel module, source
> code revision) that could account for this? It would be in the networking
> code, possibly the socket demultiplexer. I have looked for this for a
> while and just cannot find it. This change would be after Fedora 12.
> Any hint would be appreciated.

It might be related to keeping the processing on the same cpus to improve
cache use.
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Old 08-18-2010, 09:11 PM
Robert Arkiletian
 
Default Fedora 13 networking performs extremely well

On Wed, Aug 4, 2010 at 8:33 AM, Uwe Zimmermann <uwe@gambitcomm.com> wrote:
>
> Hello,
>
> our product "MIMIC Simulator" has been running on Fedora for a long time
> (eg. see
>
> http://www.gambitcomm.com/site/support/support_platforms.shtml
>
> ). *But, we have seen a steady decline in performance over successive
> versions of Fedora (eg. see
>
> http://gambitcomm.blogspot.com/2010/06/mimic-1030-performance-test-report-high.html
>
> Our application is somewhat unique in that it can create many (10s of
> thousands) IP aliases, opens sockets to multiple ports on each.
>
> Only with Fedora 13 (kernel version 2.6.33.6-147.fc13.x86_64) have we
> seen a surprising performance improvement, where running 20,000 simulated
> agents is the same as running 10, in terms of networking performance. At
> first we could not believe it, but subsequent tests have confirmed that
> we indeed are seeing the improved performance. The specific improvement
> seems to be that the kernel seems to be efficiently demultiplexing among
> all open sockets to deliver received messages from the network card.
>
> Can some expert point me at a specific fix (spec, kernel module, source
> code revision) that could account for this? It would be in the networking
> code, possibly the socket demultiplexer. I have looked for this for a
> while and just cannot find it. This change would be after Fedora 12.
> Any hint would be appreciated.
>
> Thank you in advance.
>
> Uwe Zimmermann
> Gambit Communications

F13 uses 2.6.33 but I know 2.6.35 has an improvement that could also
benefit you. Maybe Fedora devs included it in F13 but I doubt it.

>From http://www.h-online.com/open/features/What-s-new-in-Linux-2-6-35-1047707.html?artikelseite=1;page=2

"Google developer Tom Herbert submitted two major improvements to the
network subsystem of Linux 2.6.35: Receive Packet Steering (RPS) and
Receive Flow Steering (RFS). RPS distributes the processing steps for
handling received network packets across the available processor cores
so that these can work in parallel from the protocol layer onwards.
RFS, together with other functions, is said to offer a software
emulation of the multi-queue functionality found in network cards
(NICs).

RFS, the second technology, is based on the first and tries to assign
the processing of layer 3 and 4 of the network protocol directly to
the processor core which runs the userspace application that will
eventually accept and process the network data. The kernel hacker
gives a rough overview of how this is done in his commit comment in
the source code management system. This comment also contains various
test results which show that the throughput is increased a little
further with RFS; the benchmark results also show considerably shorter
latencies. Further details about these technologies can be found in an
article about RPS and RFS on LWN.net."

More technical info at LWN.net
http://lwn.net/Articles/362339/
https://lwn.net/Articles/382428/


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Robert Arkiletian
Eric Hamber Secondary, Vancouver, Canada
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