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incoming packet latency in 2.4.[18-20]

DISCUSSION Chris Friesen 3 participants 3 messages Oct 15, 2003

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Chris Friesen

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There is an issue with incoming packet latency in the kernels mentioned.

It seems that if you send in a burst of messages, the amount of time it takes to wake the listening process is dependent on the size of the message burst. 2.4.18-2.4.20 all show this behaviour, 2.6 doesn't.

Some numbers for a udp message size of 2 bytes:

1 packet, average latency 12 usecs
10 packets, average latency 66 usecs
100 packets, average latency 477 usecs

Is this a known issue? Is there an easy way to fix this, or is it something inherent in the 2.4 architecture?

Thanks,

Chris

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Chris Friesen                    | MailStop: 043/33/F10
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#1 lore raw

Have you tried a more recent kernel?

Matt H.

Quoted 18 lines · Chris Friesen

There is an issue with incoming packet latency in the kernels mentioned.

It seems that if you send in a burst of messages, the amount of time it takes to wake the listening process is dependent on the size of the message burst. 2.4.18-2.4.20 all show this behaviour, 2.6 doesn't.

Some numbers for a udp message size of 2 bytes:

1 packet, average latency 12 usecs
10 packets, average latency 66 usecs
100 packets, average latency 477 usecs

Is this a known issue? Is there an easy way to fix this, or is it something inherent in the 2.4 architecture?

Thanks,

Chris

#2 lore raw
In reply to Chris Friesen
Quoted 7 lines · On Wed, 15 Oct 2003 11:45:52 -0400 Chris Friesen <[email protected]>…

There is an issue with incoming packet latency in the kernels mentioned.

It seems that if you send in a burst of messages, the amount of time it takes to wake the listening process is dependent on the size of the message burst. 2.4.18-2.4.20 all show this behaviour, 2.6 doesn't.

Quoted 8 lines

Some numbers for a udp message size of 2 bytes:

1 packet, average latency 12 usecs
10 packets, average latency 66 usecs
100 packets, average latency 477 usecs

Is this a known issue? Is there an easy way to fix this, or is it something inherent in the 2.4 architecture?

Can you verify these numbers with 2.4.22 and 2.4.23-pre7 ?

Regards,
Stephan