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To: Peter Jeremy <peterjeremy@optushome.com.au>
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Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org,
	Andre Oppermann <andre@freebsd.org>
Subject: Re: Much improved sendfile(2) kernel implementation
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On Thu, 21 Sep 2006, Peter Jeremy wrote:

> On Wed, 2006-Sep-20 23:59:13 +0200, Andre Oppermann wrote:
>> I have rewritten kern_sendfile() to work in two loops, the inner which 
>> turns as many pages into mbufs as it can up to the free send socket buffer 
>> space.
>
> The 64K blocks sounds good but how does this interact with TCP slow start? 
> Is there the possibility that a couple (for some reasonably large value of 
> 'couple') of TCP connections slowly accepting a file could eat all the mbuf 
> space?

In principle, existing socket buffer resource limits are the way to prevent 
this from happening -- sendfile() should continue to obey them as before, we 
are just better able to use the available buffer space if it exists.

Robert N M Watson
Computer Laboratory
University of Cambridge