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Date: Mon, 27 Oct 1997 21:57:50 -0500 (EST)
From: Alfred Perlstein <perlsta@cs.sunyit.edu>
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To: Mike Smith <mike@smith.net.au>
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Subject: Re: help with fstat? 
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thank you, i just wasn't sure of a way to go at this, but now mmap seems
awesome.

On Tue, 28 Oct 1997, Mike Smith wrote:

> > don't want to look a gift answer in the mouth but i don't think this is a
> > good idea, i'm working on a distributed system for transfering files
> > across the internet.  the system is supposed to be able to manage a large
> > load of file transfers over TCP.
> 
> On the contrary, it's an *excellent* idea.
> 
> > if i mmap tons of files across many processes i think i will cause a large
> > amount of unnessesary paging, as most of the files will be in the
> > 200k-5meg range this will be too much laod on the system.
> > 
> > unless mmap() maps in on demand... but i think i'll be eating up all my
> > address space...
> 
> mmap() just associates a region of your address space with the file; 
> until you actually reference it, you won't get any paging activity.
> 
> As for eating up your address space, if you're only dealing with little 
> files like you describe you won't have any trouble at all.  I'm 
> regularly mapping files in the 100M range, and it beats the hell outa 
> reading them in record by record.
> 
> > isn't fstat supposed to be what i'm looking for?
> 
> No.
> 
> > i don't want to exhaust the virtual memory on the machine, just get
> > optimal transfers.
> 
> You won't exhaust virtual memory; mmapped regions are backed by the 
> file, not by swap.
> 
> mike
> 
> 
>