CRR (S): 7099849: G1: include heap region information in hs_err files

[Tony Printezis]

Hi all,

(I'm also copying the runtime alias, as this change will concern them too)

I'd like to get a couple of reviews for this change:

http://cr.openjdk.java.net/~tonyp/7099849/webrev.0/

Some background: when trying to track down issues in G1 it is often very 
helpful to know what type of regions the heap has and/or get information 
on a particular region (whether it's humongous, whether it's young, how 
full it is, etc.). We thought it'd be a good idea to include the 
per-region information in the hs_err file to always have it available 
after a crash.

I don't think the changes in the webrev are too controversial. The 
reason I wanted to give a heads up to both groups was to point out that 
this change will increase the size of the hs_err files when G1 is used. 
It's common to have 1,000 to 2,000 regions in the heap, if larger heaps 
are used (much fewer if smaller heaps are used), which means that the 
hs_err file will have this many extra lines. Does anyone have any 
concerns about this?

I attached an example hs_err file obtained from a workspace with this 
change applied.

BTW, I also cleaned up a bit the way the print() methods on the heap are 
defined (I pushed the default behavior to the superclass, where possible).

Tony

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