Re: question on incoming packets and scheduler
From: Chris Friesen
Date: Wed Oct 15 2003 - 15:14:20 EST
Davide Libenzi wrote:
On Wed, 15 Oct 2003, Chris Friesen wrote:
It appears that 2.4.20 fixes this issue, but there is another one
remaining that the latency appears to be dependent on the number of
incoming packets. See thread "incoming packet latency in 2.4.[18-20]"
for details. This behaviour doesn't show up in 2.6, and I'm about to
Are you sure it's not a livelock issue during the burst?
I dunno, you tell me.
The test app simply sits in select() until a packet comes in, then it
spins on recvmsg() until there are no more messages. It uses
SO_TIMESTAMP to find out when the packet got to the kernel, and does a
gettimeofday() right after the recvmsg(), then calculates the delta for
each packet and the overall average.
With 2.4.[18-20], the overall average goes up when the number of packets
goes up. For 2.6.0-test6, it stays constant.
Chris Friesen | MailStop: 043/33/F10
Nortel Networks | work: (613) 765-0557
3500 Carling Avenue | fax: (613) 765-2986
Nepean, ON K2H 8E9 Canada | email: cfriesen@xxxxxxxxxxxxxxxxxx
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