JEP 271: Unified GC Logging - Third pre-review

Bengt Rutisson bengt.rutisson at
Mon Nov 16 12:17:14 UTC 2015

Hi Kirk,

On 2015-11-13 19:49, Kirk Pepperdine wrote:
> Hi Bengt,
> GC(5) seems to be missing. from 
> <>

Good catch. This is a problem with the way CMS (or rather 
GenCollectedHeap) can skip a young GC and directly kick off a full 
collection if it finds that the young collection would fail. The way 
GenCollectedHeap::do_collection() handles the two types of collections 
that it can start is too complex in my opinion.

This is the same code that makes this log:

look like collection number 5 and 3 come in the wrong order.

(See the "Even more details..." section in my first pre-review:

I will file an RFE to fix this but it is not really a logging problem. 
It is more of a code structure problem. So, I would like to fix this 
separately after the big unified logging change has been pushed. The new 
logging just makes it more visible.


> Regards,
> Kirk
>> On Nov 13, 2015, at 9:56 AM, Bengt Rutisson 
>> <bengt.rutisson at <mailto:bengt.rutisson at>> wrote:
>> Hi everyone,
>> Here is an updated pre-review for the work for JEP 271 Unified GC 
>> Logging.
>> Now it includes all the logging that I plan on converting for the 
>> first step.
>> Here are examples from the latest prototype:
>> <>
>> The webrev for the changes is available here:
>> Some changes that have been made:
>> - GC id is now logged as "GC(5)" instead of the previous "GC#5"
>> - The CMS and G1 concurrent logging have been homogenized to look 
>> similar. All concurrent phases are start with "Concurrent" and now 
>> include timestamps.
>> - The paused phases now all start with "Pause".
>> - The log messages from the different collectors now look more 
>> similar. For example "Pause Young" is used for young GCs for all 
>> collectors instead of for example "Young pause" for G1 and "Pause. 
>> ParNew" for CMS.
>> - I've added a line at the start of the log to clearly state what GC 
>> is selected.
>> Thanks,
>> Bengt

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