Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.misc
Subject: Re: Query
Message-ID: <60345@lanl.gov>
Date: 16 Aug 90 23:17:00 GMT
References: <126800008@.Prime.COM>
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 18

From article <126800008@.Prime.COM>, by EAF@.Prime.COM:
> [...]
>                                                             If your
> language I/O library is intelligent and you are reading sequential
> data, the language library will call on the OS to read the next disk
> block into memory, often before it is required.
> [...]

Not on UNIX it won't.  There is no system call for the library to use
which will start a read request and then return control to the library
while the read is asynchronously processing.  So, there's no point in
the library trying to read ahead, the system will cause the same delay
(statistically - there are variations independent of a given process)
whether you read ahead or not.

This is one of the most glaring deficiencies of UNIX.

J. Giles