CMS GC Log

[Y.S.Ramakrishna at Sun.COM]

On 10/11/09 17:58, Sujit.Das at cognizant.com wrote:
> Trying to understand CMS-IM and CMS-RM log messages.
>  
> *1. CMS Initial Mark*
> 7465.472: [GC [1 CMS-initial-mark: 1370720K(2739200K)] 1384764K(3058176K), 0.0995109 secs]
> In above log snippet, CMS IM was triggered at the old gen occupancy of 
> 1370720 K with total size of old gen size as 2739200 K. What does 

Right.

> 1384764 K and 3058176 K represent?

Current total heap occupancy and current total heap capacity. (excluding perm gen).

> *2. CMS Remark*
> 7475.403: [weak refs processing, 0.0024767 secs] [1 CMS-remark: 
> 1401865K(2739200K)] 1582866K(3058176K), 0.1290017 secs]
>  
> Similarly in above log snippet, CMS RM was triggered at the old gen 
> occupancy of 1401865 K with total size of old gen size as 2739200 K. 
> What does 1582866 K and 3058176 K represent?

Same as what i wrote above for CMS-IM.

>  
> Also, in GC output is there any way we can determine heap space used 
> before and after a CMS collection? This is printed for minor collection 
> but not sure if this is printed for CMS collection.

The above is basically all you get. Typically the free space peaks towards
the end of the CMS-sweep and reaches its minimum typically around or just
after the start of the sweep (i.e. around the CMS-remark phase).

-- ramki

>  
> Thanks,
> Sujit
>  
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