Moore's law and why persistence may not be necessary.

Cees de Groot cg at home.cdegroot.com
Wed Jan 23 16:23:10 UTC 2002


Scott A Crosby <crosby at qwes.math.cmu.edu> said:
>But, fullGC has *no locality* and will just *die*.
>
I doubt it - at least under Linux. I used to run a UUCP/Fido gateway with
Cnews on a 386 with 4Mb RAM when Linux just appeared. The daily newsspool
cleanup job (where Cnews wanted all sorts of stuff in core) started at 4am and
the machine trashed until well after lunch every day ;-)

>And, does squeak *really* need a persistence engine, other than the image?
>Who, unless they're storing multimedia into the image, is going to have an
>image that big in practice? Multimedia can be easily dumped into
>ImageSegments.
>
I think it does. Clearly, your full-text thing would benefit for ease of use.
I think that saving the image is too slow and too big a hammer for saving,
say, a new contact - especially if you're living in a big
multi-hundred-megabyte image.

Plus, if SqueakNOS is to become a reality, it either needs a filesystem or
something else to put all the stuff that Squeak currently uses the filesystem
for (like, err, storing ImageSegments :-)). 

Now, I'm a complete idiot w.r.t. the object memory, so maybe it is possible
to save only dirty chunks and do some memory-mapping like activities so that
the above things would be possible. I'll start to talk about transactions in
that case ;-). 

This discussion probably slowly moves into the direction of a philosophical
discussion. Is the object memory an object database? Should it be extended
that way? Think SqueakNOS: just an image that fills, say, a harddisk partition
or flash drive? Or an image plus all sorts of stuff on a Squeak-based
filesystem/OODB external to the image?

>I learned an important lesson from a friend. Computers are getting so much
>better, than many times old decisions should be rethought out. I see this
>lesson all over the place, from the delayed Itanium, to diskbasing a
>dbase. Wait too long, and your design decisions are crap. :)
>
I agree. The requirements (persistence, transactions) won't change, however.
Just the solutions implemented to satisfy the requirements.

-- 
Cees de Groot               http://www.cdegroot.com     <cg at cdegroot.com>
GnuPG 1024D/E0989E8B 0016 F679 F38D 5946 4ECD  1986 F303 937F E098 9E8B



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