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RE: On PATH_MAX


From: Christopher Nelson
Subject: RE: On PATH_MAX
Date: Tue, 8 Nov 2005 10:04:50 -0700

> On Tue, Nov 08, 2005 at 08:51:09AM -0700, Christopher Nelson wrote:
> > > Not exactly.  If a server wants to support arbitrary long paths, 
> > > it's not going to map the whole thing into its address 
> space.  It'll 
> > > accept a container capability and map parts of it in, unmapping 
> > > other parts of it.
> > 
> > What mechanism allows it to map *parts* of a single transfer in?
> 
> There is no transfer of data, there is only transfer of the 
> container capability.  This capability gives access to a set 
> of pages, which can be mapped in or out of the address space 
> when the process likes.

You still have data transfer, even if it's only in the form of metadata.
A thread can't access any memory until it's mapped into its address
space.  If you say that a thread must only keep a handle to the metadata
that defines the memory and then map it in and out as needed, you
essentially turn the operation into an open..read..close, and you add
tremendous complexity in the form of a buffering layer to map pages in
and out.  I'm not saying its impossible, I'm saying its not a good idea,
IMHO.

-={C}=-




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