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SubjectRe: [PATCH] Re: Move of input drivers, some word needed from you
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   Date: Tue, 22 Aug 2000 13:48:23 +0200 (MET DST)
From: Bjorn Wesen <bjorn@sparta.lu.se>

Forget the circular buffer and use a chain of buffers instead on the
incoming queue. A circular buffer is just a fixed buffer-chain of 1-byte
elements, but with an overflow headache and a flipping problem..

Trust me, you don't want to re-invent BSD clists. They are a
performance disaster.

A line discipline doing raw tty I/O can do zero-copy, in the sense that
the serial driver on the receiving end gives away its received buffers to
the upper levels. Just like in the network stack.

I verymuch doubt that given all of setup overhead and general
hair/complexity necessary for zero-copy, that this would be useful *at*
*all* in any real-life application. The code is already optimized for
single-copy; given the relative speeds of serial transfer rates versus
memory copy speeds, this is a pointless optimization.

- Ted
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