Re: tcp bw in 2.6

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To: <lm@...>, Herbert Xu <herbert@...>, <torvalds@...>, <davem@...>, <wscott@...>, <netdev@...>
Date: Tuesday, October 2, 2007 - 11:41 am

Interesting data point.  My test case is like this:

server
	bind
	listen
	while (newsock = accept...)
		transfer()

client
	connect
	transfer

If the server side is the source of the data, i.e, it's transfer is a 
write loop, then I get the bad behaviour.  If I switch them so the data
flows in the other direction, then it works, I go from about 14K pkt/sec
to 43K pkt/sec.

Can anyone else reproduce this?  I can extract the test case from lmbench
so it is standalone but I suspect that any test case will do it.  I'll
try with the one that John sent.  Yup, s/read/write/ and s/write/read/
in his two files at the appropriate places and I get exactly the same
behaviour.

So is this a bug or intentional?
-- 
---
Larry McVoy                lm at bitmover.com           http://www.bitkeeper.com
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Messages in current thread:
Re: tcp bw in 2.6, Larry McVoy, (Mon Oct 1, 8:59 pm)
Re: tcp bw in 2.6, Herbert Xu, (Tue Oct 2, 6:52 am)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 11:09 am)
Re: tcp bw in 2.6, Linus Torvalds, (Tue Oct 2, 3:27 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 3:53 pm)
Re: tcp bw in 2.6, David Miller, (Tue Oct 2, 4:33 pm)
Re: tcp bw in 2.6, Roland Dreier, (Tue Oct 2, 4:44 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 5:21 pm)
Re: tcp bw in 2.6, Pekka Pietikainen, (Wed Oct 3, 5:13 pm)
Re: tcp bw in 2.6, Larry McVoy, (Wed Oct 3, 5:23 pm)
Re: tcp bw in 2.6, Pekka Pietikainen, (Wed Oct 3, 5:50 pm)
Re: tcp bw in 2.6, John Heffner, (Tue Oct 2, 2:29 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 3:07 pm)
Re: tcp bw in 2.6, Linus Torvalds, (Tue Oct 2, 3:29 pm)
Re: tcp bw in 2.6, David Miller, (Tue Oct 2, 4:31 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 3:33 pm)
Re: tcp bw in 2.6, John Heffner, (Tue Oct 2, 3:53 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 4:14 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 4:40 pm)
Re: tcp bw in 2.6, Wayne Scott, (Tue Oct 2, 4:42 pm)
Re: tcp bw in 2.6, Linus Torvalds, (Tue Oct 2, 5:56 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 11:41 am)
Re: tcp bw in 2.6, Linus Torvalds, (Tue Oct 2, 12:34 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 12:48 pm)
Re: tcp bw in 2.6, David Miller, (Tue Oct 2, 5:16 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 5:26 pm)
Re: tcp bw in 2.6, David Miller, (Tue Oct 2, 5:47 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 6:17 pm)
Re: tcp bw in 2.6, David Miller, (Tue Oct 2, 6:32 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 6:36 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 6:59 pm)
Re: tcp bw in 2.6, David Miller, (Wed Oct 3, 4:02 am)
Re: tcp bw in 2.6, Ben Greear, (Tue Oct 2, 12:48 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 1:11 pm)
Re: tcp bw in 2.6, Ben Greear, (Tue Oct 2, 1:18 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 1:21 pm)
Re: tcp bw in 2.6, Stephen Hemminger, (Tue Oct 2, 1:54 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 2:35 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 12:25 pm)
Re: tcp bw in 2.6, Stephen Hemminger, (Tue Oct 2, 12:47 pm)
Re: tcp bw in 2.6, Daniel Schaffrath, (Mon Oct 15, 8:40 am)
Re: tcp bw in 2.6, Stephen Hemminger, (Mon Oct 15, 11:49 am)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 12:49 pm)
Re: tcp bw in 2.6, Stephen Hemminger, (Tue Oct 2, 1:10 pm)
Re: tcp bw in 2.6, Linus Torvalds, (Mon Oct 1, 10:14 pm)
Re: tcp bw in 2.6, Larry McVoy, (Mon Oct 1, 10:20 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 1:14 pm)
Re: tcp bw in 2.6, Bill Fink, (Wed Oct 3, 3:19 am)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 1:20 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 2:01 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 2:40 pm)
Re: tcp bw in 2.6, Rick Jones, (Tue Oct 2, 3:47 pm)
Re: tcp bw in 2.6, David Miller, (Tue Oct 2, 5:32 pm)
Re: tcp bw in 2.6, John Heffner, (Tue Oct 2, 11:06 am)
Re: tcp bw in 2.6, David Miller, (Mon Oct 1, 11:50 pm)
Re: tcp bw in 2.6, Larry McVoy, (Tue Oct 2, 12:23 am)