Re: [9fans] mmap

[Alexander Sychev <santucco@gmail.com>]

On Tue, 29 Jul 2008 12:52:14 +0400, Enrico Weigelt <weigelt@metux.de>
wrote:

Hi!

> an full mmap() is a really nice thing. It can make a lot things
> easier if you just map the whole file into the process' memory and
> let the kernel handle the actual IO.

Yes, it is comfortable. But just think a bit - what will you do in the
mmap implementation when you had mapped a remote file (in Plan9 you can't
be sure some file is local or it is really just a file), and the
connection has just been broken? Surprise!

For example, in Windows you will have an "access violation". It is very
funny to rewrite a code for using the good old file i/o instead of mmap.
In Linux you can't map a non-regular file.

Yes, you can read entire the file into the memory, but a size of the file
can be very big and you will destroy the main advantage of mmap - the
reading of only needed pieces of the file, not entire.

I beleive, mmap is not for distributed systems.

--
Best regards,
	santucco