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

Tue Nov 1 14:08:05 UTC 2011

Hi Tony,

I hope I am not too late in providing feedback on this change. Here are 
couple of suggestions for the heap regions information in hs_err file:

- I think it would be useful to print a header before the heap regions 
details. e.g.

Heap
  garbage-first heap   total 20480K, used 11630K [0x6e600000, 
0x6fa00000, 0xae600000)
   region size 1024K, 1 young (1024K), 1 survivors (1024K)
  compacting perm gen  total 16384K, used 2604K [0xae600000, 0xaf600000, 
0xb2600000)
    the space 16384K,  15% used [0xae600000, 0xae88b3c0, 0xae88b400, 
0xaf600000)
No shared spaces configured.

*Heap Regions:*
                   0 PTAMS 0x6e600000 NTAMS 0x6e639700 space 1024K,  22% 
used [0x6e600000, 0x6e639700, 0x6e700000)
           F    17 PTAMS 0x6e700000 NTAMS 0x6e700000 space 1024K,   0% 
used [0x6e700000, 0x6e700000, 0x6e800000)
           F    17 PTAMS 0x6e800000 NTAMS 0x6e800000 space 1024K,   0% 
used [0x6e800000, 0x6e800000, 0x6e900000)

- Also, I think it would be helpful for the hs_err file reader to have 
the meanings of the acronyms also printed (as we show in the stack trace 
in hs_err file)

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, 
C=native code)
V  [libjvm.so+0xc494db]  VMError::report_and_die()+0x19b

Heap Regions: (CS=collection set, PTAMS=previous top at mark start, 
NTAMS=next top at mark start, etc...)
                17 PTAMS 0x6f200000 NTAMS 0x6f300000 space 1024K, 100% 
used [0x6f200000, 0x6f300000, 0x6f300000)
     CS SU      17 PTAMS 0x6f300000 NTAMS 0x6f38e650 space 1024K,  55% 
used [0x6f300000, 0x6f38e650, 0x6f400000)
                17 PTAMS 0x6f400000 NTAMS 0x6f493c60 space 1024K,  57% 
used [0x6f400000, 0x6f493c60, 0x6f500000)

Thanks,
Poonam

On 10/12/2011 10:19 PM, Tony Printezis wrote:
> 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
>

-- 
Best regards, Poonam

Oracle <http://www.oracle.com>
Poonam Bajaj | Principal Member of Technical Staff
Phone: +91 80 66937451 <tel:+91%2080%2066937451> | Mobile: +91 
9844511366 <tel:+91%209844511366>
Oracle JVM Sustaining Engineering

ORACLE India Bangalore
Green Oracle <http://www.oracle.com/commitment> Oracle is committed to 
developing practices and products that help protect the environment

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