Re: File/IO discussion - request for comments

[Carl Spalletta <ioanamitu@xxxxxxxxx>]

--- Jan Hudec <bulb@ucw.cz> wrote:
> On Sun, Feb 01, 2004 at 15:52:01 -0800, Carl Spalletta wrote:

> >   In a recent O'Reilly Press book "Java NIO" by R. Hitchens...

> > FIRST ALTERNATIVE: read() syscall
> > Nonblocking read..
 
> There is no non-blocking read from disk!
> There is only an aio_read, which is a different syscall.

You are correct - although I am discussing how the system
uses the pagecache which is by definition from memory.

> the mechanizm for loading pages is the
> same for read as for page-fault.

I am not sure how a simple read() of a regular file in
a disk based filesystem can generate a page fault - the
read goes to disk to get the info to copy to the userspace
buffer, while a page_fault on an uncached page of an mmapped
file uses the readpage() method.

Is this incorrect? Can you explain further?




=====
Carl Spalletta
--
They have an engine called the Press, whereby the people are deceived.

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