Costin Manolache wrote:
Good point, fixing jasper servlet is a not going to help in production
env ( and precompiled jsps), so it's probably not worth it.
However - I disagree that JSPs are 'just' servlets - or at least they
should not be plain and stupid translation of text to 'println'
servlets. The current behavior of jsps wrt memory is horrible if you
have lot of content - all the plain text ends up in memory, as part of
the class. It's good for cheating on benchmarks - bad for production.
There are far better ways to use the memory.
The alternative is wasting CPU and disk reading stuff from disk all over
again for nothing, which for most servers are even more useful
resources. We're talking about using less than 128MB of memory here, so
it's not too much (who has more than 128MB of static text in his JSPs ?).
If you're interested in the lowest footprint, JSP is not the right
technology: you need a templating (or anything not compiled) technology
and disable its caching features (it will be quite slow, but will use
minimal amounts of resident memory). The only solution is to forbid
scriptlets (or as an option use a processing when a page does not
contain scriptlets - and of course, rewrite a significant amount of
Jasper - way cool :D), in which case compilation is not needed, and we
can simply execute the nodes (memory is saved by optionally discarding
the nodes between requests).
IMO separating the strings and loading/unloading them using a cache
would help a lot in such situations ( i.e. large number of jsps ==
huge memory use ). Unloading not frequently/recently used jsps ( and
servlets, and webapps ) might also be very nice, assuming they can
handle being unloaded. But I agree that the current patch is not the
right solution.
Unloading the servlet's instance is possible, not the class definition.
Unloading webapps is not possible at the moment (even if it was, modern
webapps take ages and tons of resources to start, so it wouldn't be
practical IMO).
It still doesn't cost much to give some more perm gen to Sun's VM (still
a fairly manageable amount IMO, but of course, if you want to do hosting
or it's an embedded situation, it's a problem).
BTW, I am ok with shipping additional presentation technologies with
Tomcat, we do not need to give JSP any special treatment anymore.
Rémy
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