repos $ du -hc $(ls */lib/*.jar) | fgrep total
291M total
Cost (on standard disks): < 5 cents.
Sorry, that's tiny. It's even less than 0.5% of the small SSD I have
in
my laptop.
Seriously, this is just premature optimization.
You're seriously fine with every single Leiningen-based project
spitting a redundant copy of Clojure, contrib, and whatever other
dependencies it needs onto disk, and doing so every time it picks up a
new snapshot? That every tiny library you pull off GitHub grabs
another few dozen MB, rather than a few dozen KB?
290MB is only tiny if you have an empty disk. 290MB here, 290MB there,
and suddenly the 13GB free on my 180GB laptop disk starts looking
mighty cramped. I have a lot of stuff I'd rather store on that disk
than 290MB of redundant jar copies. Those hundreds of megs get backed
up, scanned, indexed, defragmented, yadda yadda. What a waste.
You might also be overlooking disk caching, paging, JVM memory
sharing, and other performance effects from having multiple instances
of the same jars in memory. I know that the Mac JVM does some tricks
to share memory in this way.
Furthermore, it's slower to copy 28MB of jars than it is to symlink
them:
$ time cp -R lib /tmp/foo
real 0m2.981s
user 0m0.007s
sys 0m0.152s
... surprise disk slowdown! All the nonsense of looking up snapshots,
checking deps against the Maven repo, etc. already takes so much time
that I dislike using Leiningen. Anything to bring that down by a few
hundred milliseconds and a few fewer disk head slaps would be nice.
There is no engineering reason to blindly copy jars into lib/. Hard
links, symlinks, or computed classpaths are all better solutions in
every single way.
"Premature optimization" is the act of expending significant time
addressing a performance problem prior to measurement, typically
allowing unmeasured performance concerns to affect system design.
Using symlinks instead of copying would not be a significant amount of
work, doesn't affect the overall design, and we're hardly flying
blind. You're using the wrong phrase. Here's a different Knuth quote:
"In established engineering disciplines a 12 % improvement, easily
obtained, is never considered marginal and I believe the same
viewpoint should prevail in software engineering"
I'd call this a decent improvement, and it's certainly easily obtained.
Whatever happened to engineers building a decent solution out of a
sense of pride, or even making the most basic half-assed attempt to
conserve resources?
Sometimes I despair.
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