Direct promotion to old gen

Sujit.Das at Sujit.Das at
Mon Aug 3 10:18:39 PDT 2009

Hi All,
I am trying to capture statistics to denote direct promotion from young gen to old gen.
As per my understanding, minor collection will empty eden space and put surviving objects into 'To' survivor space. Objects that have survived more than Max Tenuring Threshold value will get promoted. Example: If max Tenuring Threshold is 4, then in age 4 size that gets printed in verbose GC output will be the size that should get promoted in old gen as part of next minor collection. Anything more than previous age4 size is result of direct promotion from eden space to old gen.
Please confirm my understanding / approach. If above understanding is correct, I plan to get plot of
(Promo from current minor collection - Age4 from previous minor collection)
The values will help me to determine whether I need to tune my eden and survivor spaces.
Your help much appreciated.

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