Re: [PATCH] TCP Zero Copy for mmapped files

From: Larry McVoy (lm@bitmover.com)
Date: Thu Jan 02 2003 - 17:28:16 EST


> > 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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