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Date: Thu, 2 Jan 2003 14:28:16 -0800
From: Larry McVoy <lm@bitmover.com>
To: Thomas Ogrisegg <tom@rhadamanthys.org>
Cc: "David S. Miller" <davem@redhat.com>, linux-kernel@vger.kernel.org,
       Larry McVoy <lm@bitmover.com>
Subject: Re: [PATCH] TCP Zero Copy for mmapped files
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> > 1) Does not handle writes that straddle multiple VMAs
> 
> What exactly do you mean? In my test, files larger than a
> page were handled perfectly, as well.

	mmap(file1 at location [a,b)
	mmap(file2 at location [b,c)
	write(sock, a, (size_t)(c - a));

> However, I didn't like the VM waste either, but I believe there
> is no other way.

The VM cost hurts.  Badly.  Imagine that the network costs ZERO.  Then
the map/unmap/vm ops become the dominating term.  That's why it is a
fruitless approach, it still has a practical limit which is too low.
-- 
---
Larry McVoy            	 lm at bitmover.com           http://www.bitmover.com/lm 
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