[TUHS] Re: 'Huge' file support removed from PWB1

[Jonathan Gray <jsg@jsg.id.au>]

removed in PWB/UNIX 1.0.

ifdef'd out in the Harvard/Radcliffe Student Time-sharing System (HRSTS)
parts found in tuhs/Applications/Usenix_77. h/distrib.note includes:

'4.	"Huge" files are not supported by our modifications.  This is not
necessarily a hard restriction, however we early on decided
we wanted no more than one level of indirection all the way up to 1 megabyte,
and had no need for larger files.  The incompatibilities may be minimal,
but we have not even bothered to seek them out.'

On Thu, Mar 09, 2023 at 03:21:19AM -0500, Kenneth Goodwin wrote:
> I have not seen the UNIX kernel source code in quite a while, but as I
> recall the double indirect block algorithm did not kick in until the file
> exceeded a certain threshold. So it would not make sense to remove the code
> for performance reasons.
> 
> Perhaps this is more likely due to the use of larger logical block sizes....
> 
> Is the code physically removed or IFDEF'd out for conditional compilation?
> 
> Perhaps someone decided that programmers would never need to test code on
> large files..
> 
> On Wed, Mar 8, 2023, 8:10 AM Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
> 
> > In PWB1, support for 'huge' files appears to have been removed. If one
> > compares bmap() in PWB1'S subr.c with V6's, the "'huge' fetch of double
> > indirect block" code is gone. I guess PWB didn't need very large (>
> > 8*256*512
> > = 1,048,576 bytes) files? I'm not sure what the _benefits_ of removing it
> > were, though - unless PWB was generating lots of files of between 7*256*512
> > and 8*256*512 bytes in length, and they wanted to avoid the overhead of the
> > double-indirect block? (The savings in code space are derisory - unlike in
> > LSX/MINI-UNIX.) Anyone know?
> >
> >                 Noel
> >