netdev - Re: tcp bw in 2.6

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Date:	Tue, 02 Oct 2007 12:47:41 -0700
From:	Rick Jones <rick.jones2@...com>
To:	Larry McVoy <lm@...mover.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	davem@...emloft.net, wscott@...mover.com, netdev@...r.kernel.org
Subject: Re: tcp bw in 2.6

Larry McVoy wrote:
> On Tue, Oct 02, 2007 at 11:01:47AM -0700, Rick Jones wrote:
> 
>>has anyone already asked whether link-layer flow-control is enabled?
> 
> 
> I doubt it, the same test works fine in one direction and poorly in the other.
> Wouldn't the flow control squelch either way?

While I am often guilty of it, a wise old engineer tried to teach me that the 
proper spelling is ass-u-me :)  I wouldn't count on it hitting in both 
directions, depends on the specifics of the situation.

WRT the HP-UX ACK avoidance heuristic, the default HP-UX socket buffer/window is 
32768, and tcp_deferred_ack_max defaults to 22.  That isn't really all that good 
a combination - with a window of 32768 11 for the deferred ack would be better. 
  You could also go ahead and try it with a value of 2.  Or, bump the window 
size defaults - tcp_recv_hiwater_def and tcp_xmit_hiwater_def - to say 65535 or 
128K or something - or use the setsockopt() calls to effect that.

rick jones
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