(Slightly OT) Telling exactly which objects get promoted

Jon Masamitsu jon.masamitsu at oracle.com
Thu Apr 8 07:10:21 PDT 2010

On 04/08/10 03:26, Ben Evans wrote:
> Hi,
> Apologies if this is too off-topic, or is covered in a document which 
> my Google-Foo has been insufficient to locate so far.
> I have an application which is displaying an odd collection pattern on 
> large heaps (3G on a 32-bit 6u18). Broadly, all our objects are 
> sufficiently short-lived that we don't expect any of them to survive 
> to tenure, and yet a small amount of them seem to, so over time we are 
> unable to completely avoid full collections.

Even short lived objects will survive a collection if the collection 
happens right after the
objects are allocated.  Try increasing MaxTenuringThreshold and maybe 
increasing the size
of your survivor space sizes.
> We would like some tool or JVM setting which would allow us to see 
> exactly which objects (or failing that, their classes) are reaching 
> tenure. Can anyone suggest something suitable, or some docs?
> Thanks,
> Ben
> -- 
> Ben Evans
> GFFX Auto Trading
> Deutsche Bank, London
> Office: +44 (0)20 7541 3953
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