netdev - RE: [PATCH net-next] tcp: auto corking

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Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B7470@saturn3.aculab.com>
Date:	Fri, 6 Dec 2013 17:57:44 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Eric Dumazet" <eric.dumazet@...il.com>,
	"Rick Jones" <rick.jones2@...com>
Cc:	"David Miller" <davem@...emloft.net>,
	"netdev" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next] tcp: auto corking

> Well written applications use TCP_CORK or MSG_MORE, but unfortunately
> many applications are not well written.

If you know you have multiple buffers to send, you can use writev()
and save all the system calls.
The problem is applications that don't know that they are going to
have more data in a few microseconds.

Buffering data until the skb for earlier messages have been freed
seems to be highly reliant on the mac driver taking 'end of transmit'
interrupts - even more so than usual. I guess that drivers offering
small queue counts are generating those interrupts.

	David