netdev - Re: [RFC] tcp: use order-3 pages in tcp

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Date:	Fri, 21 Sep 2012 17:48:31 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	David Miller <davem@...emloft.net>, subramanian.vijay@...il.com,
	netdev@...r.kernel.org
Subject: Re: [RFC] tcp: use order-3 pages in tcp_sendmsg()

On Thu, 2012-09-20 at 22:25 +0200, Eric Dumazet wrote:
> On Thu, 2012-09-20 at 13:06 -0700, Rick Jones wrote:
> 
> > 
> > Yes, I was being too fast and loose with my wording, paying more 
> > attention to the netperf tests than the rest of it.  While loopback may 
> > be lossless, TCP retransmissions over loopback shouldn't be all *that* 
> > surprising.
> 
> Sending perfect packets (large packets) should trigger no retransmits.

By the way, with current MTU of 16436 on loopback, max packet size is
48KB (3 MSS)

Using an mtu of 65536 allows another 25% increase of bulk performance...

(and less potential reordering effects, as a packet contains one MSS
instead of three)

There is probably a reason why lo default MTU is 16436 ?


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