Re: Exe compression... and a nice tip.

From: Raptor (bogus_at_none.com)
Date: 02/22/05 

Date: Tue, 22 Feb 2005 00:56:51 -0800

Maarten Wiltink <maarten@kittensandcats.net> wrote in message
news:421aeda7$0$28994$e4fe514c@news.xs4all.nl...
> "Raptor" <bogus@none.com> wrote in message
> news:cve3hh01onh@news2.newsguy.com...
> > Bruce Roberts <ber@bounceitattcanada.xnet> wrote in message
> > news:qToSd.2970$uO.220364@news20.bellglobal.com...
>
> >> But have you considered the real performance cost? When a compressed
> >> exe is used it is no longer possible to simply toss executable pages
> >> when swapping takes place. They actually have to be written to the
> >> swap file. Nor can code be shared by multiple instances.
> >
> > Are you saying that the EXE is not decompressed to look like the
> > native app in memory?
>
> No, it is, and he's not saying it isn't. But with an uncompressed
> executable, pages of loaded code are interchangeable with the disk
> image. So when memory gets short, code pages can be simply thrown
> away and reloaded when they're needed again, and the latter is a
> simpler operation than you might think. Also, when two instances are
> running, a single page of code can be mapped into both processes'
> address space, saving physical memory.
>
> A compressed executable is decompressed into a data segment. That data
> segment belongs to a single process and can't be shared. And when it's
> swapped out, it needs to be saved in the page file because it's not an
> exact copy of something on disk.
>
> So you're expending disk I/O to save disk space. Guess which one is
> the cheapest part of your computer, and which is the most expensive?

Hard disk space (5.25") started out at about $100+ per megabyte. I haven't
priced it recently (I have a couple of 40 GBs which serve my needs,
including video recording, perfectly well), but we have to be pushing a
gigabyte per $1 .

My only motive for crunching an EXE file would be to save on distro/download
costs, but I have to wonder if ZIPping isn't just about as good without the
drawbacks.

Raptor

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