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Date:      Mon, 9 Feb 1998 02:37:20 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        reilly@zeta.org.au (Andrew Reilly)
Cc:        mike@smith.net.au, tlambert@primenet.com, dyson@FreeBSD.ORG, abial@nask.pl, freebsd-current@FreeBSD.ORG, jkh@FreeBSD.ORG
Subject:   Re: Custom init(8) (and some ideas)
Message-ID:  <199802090237.TAA22548@usr06.primenet.com>
In-Reply-To: <199802082219.JAA03349@gurney.reilly.home> from "Andrew Reilly" at Feb 9, 98 09:19:11 am

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> If this is likely to become a popular game (paging from compressed
> binaries),  would it be useful to build a special "binary gzipper" that
> split and separately compressed independent 4k pages?  I believe that
> the V.42 compression in modems forces blocking at 256-byte boundaries,
> to minimise the amount that needs to be re-transmitted on errors, and
> that still manages reasonable error rates.  You would need to build a
> table of pointers to each of the blocks to avoid scanning the whole
> thing, but there could be some gain.  Is there an obvious reason for
> this not to work?

If you could be *guaranteed* that the compressed imaged of 8k would
become at most 4k, then you could do page doubling.

The problem is that you need a VM object for the executable to grab
pages off of on page boundries, and you *also* need to grab pages
off of disk in page boundries.  The closest thing to this currently
is the vn? devices configured by vnconfig.  They just *happen* to
present 4k as 4k; they could just as easily present a smaller amount
as 4k (after uncompression).  You would *still* have the block-boundry
issues, though.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.

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