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Date: Tue, 27 May 1997 23:01:00 -0400 (EDT)
From: Christopher Sedore <cmsedore@mailbox.syr.edu>
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To: "Justin T. Gibbs" <gibbs@plutotech.com>
cc: "Ron G. Minnich" <rminnich@Sarnoff.COM>, FreeBSD-Hackers@FreeBSD.ORG
Subject: Re: async socket stuff 
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On Tue, 27 May 1997, Justin T. Gibbs wrote:

> >Now, in the case of a 10MB file, you've essentially saved 20MB worth of
> >memory bandwidth/time for transfer (since the data has to be copied into
> >user space on read, and back again on write), plus 160*2=320-1=319 system
> >calls avoided.
> 
> If you use an async I/O facility, there is no additional copy since you've
> pre-allocated the buffer and I/O from the file goes directly into and out
> of your user space buffer.  Since your main complaint seems to be memory
> bandwidth and the system call overhead is really quite small (FreeBSD can
> do thousands of system calls a second on a P90), I think that async I/O
> would completely solve your problem.  There is already work underway to
> bring async I/O to FreeBSD. 

I didn't know whether the async implementation would provide this or not.

I still view too many syscalls as undesirable.  This overhead seems a
shame.

-Chris