RFR 8146991: Introduce per-worker preserved mark stacks in ParallelGC

Tony Printezis tprintezis at twitter.com
Fri Mar 4 00:15:12 UTC 2016

Thomas (and all),

Updated webrev with the changes below:



On March 3, 2016 at 7:02:03 PM, Tony Printezis (tprintezis at twitter.com) wrote:


Thanks for looking at it. See inline...

On March 3, 2016 at 9:35:26 AM, Thomas Schatzl (thomas.schatzl at oracle.com) wrote:

Hi Tony, 

On Tue, 2016-03-01 at 13:22 -0500, Tony Printezis wrote: 
> Hi all, 
> These are the per-worker preserved mark stack changes for ParallelGC: 
> http://cr.openjdk.java.net/~tonyp/8146991/webrev.0/ 
> They are similar to the ParNew changes and rely on some classes I 
> introduced then. 

- In PSPromotionManager::initialize(), please extract the 
"ParallelGCThreads + 1" calculation into a local variable. 


- nitpick: the comment in PSPromotionManager::post_scavenge(), since it is a proper sentence, start with upper case and end with full stop. 


- in PreservedMarksSet::restore(), I would prefer if the total_size 
were calculated as the marks are restored. I do not see a particular 
reason why you would need to calculate this beforehand, and it is an 
extra loop over a potentially large number of threads. 

I can accumulate the size incrementally, so the output should be done at the end of the method then?

Like PreservedMarks::get() returned the number of preserved marks, and 
the method just added them together. 

- I personally dislike the use of "counter-variable += 1" in the 
increment section of for-loops, and prefer using a post-decrement. Feel 
free to ignore this comment. 

I’ve always done it this way, ++i / i++ as a statement just looks weird...

> Quick question on this: I moved: 
> log_trace(gc, ergo)("Restoring " SIZE_FORMAT " marks", total_size()); 
> to the shared code so that the message is logged irrespective of GC 
> (for example, I don’t think we were logging this for ParNew or 
> DefNew). Is “ergo” the right category here though? 

- I would remove the "ergo" tag, and try to make the message more 
meaningful, as the "gc" tag is the catch-all bucket. E.g. something 
like "Restoring... marks after evacuation failure.". 

Done. I’ll post a new webrev shortly…


Otherwise it looks good to me. I will run it through jprt and some test 



Tony Printezis | JVM/GC Engineer / VM Team | Twitter

tprintezis at twitter.com


Tony Printezis | JVM/GC Engineer / VM Team | Twitter

tprintezis at twitter.com

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