why this young gc is so slow?

Igor Veresov igor.veresov at oracle.com
Mon Aug 22 02:51:57 PDT 2011


 Right. But how big do they get at the time you see the pauses you'd like to optimize? If they're rather large consider making them smaller. That will come at price (most probably) of having full GCs happening sooner. 

Also, if you're interested in low pause times you might want to try G1 or CMS. 

igor

On Monday, August 22, 2011 at 1:34 AM, BlueDavy Lin wrote:

> The app use default Parallel GC,so survivor space will be adjusted on the fly...
> 
> 2011/8/20 Igor Veresov <igor.veresov at oracle.com (mailto:igor.veresov at oracle.com)>:
> > How big are the survivor spaces (you can get this info by running with -XX:+PrintHeapAtGC)?
> > 
> > It seems that now it spends most of the time in steal-task, which is basically traversal of the subgraph that is in eden+survivor spaces and copying.
> > 
> > igor
> > 
> > On Friday, August 19, 2011 at 8:12 PM, BlueDavy Lin wrote:
> > 
> > > I change the code,so avoid the old gen contains a huge data structure
> > > ref to young gen,now the ygc time reduce to about 40ms,live objects
> > > about 8m,but I think it should be faster than current,I'll see the
> > > code more detail.
> > > 
> > > current the gc task timestamps is:
> > > VM-Thread 298267312 298296585 298312254
> > > GC-Thread 0 entries: 11
> > > [ old-to-young-roots-task 298267525 298267593 ]
> > > [ old-to-young-roots-task 298267596 298267642 ]
> > > [ thread-roots-task 298267643 298267664 ]
> > > [ thread-roots-task 298267666 298267679 ]
> > > [ thread-roots-task 298267680 298267688 ]
> > > [ thread-roots-task 298267690 298267699 ]
> > > [ thread-roots-task 298267703 298267713 ]
> > > [ thread-roots-task 298267752 298267760 ]
> > > [ thread-roots-task 298267762 298267768 ]
> > > [ thread-roots-task 298267771 298267861 ]
> > > [ steal-task 298267862 298296339 ]
> > > GC-Thread 1 entries: 6
> > > [ thread-roots-task 298267623 298267739 ]
> > > [ thread-roots-task 298267743 298267764 ]
> > > [ thread-roots-task 298267766 298267775 ]
> > > [ thread-roots-task 298267776 298267818 ]
> > > [ thread-roots-task 298267820 298267835 ]
> > > [ steal-task 298267836 298296403 ]
> > > GC-Thread 2 entries: 8
> > > [ old-to-young-roots-task 298267585 298267715 ]
> > > [ thread-roots-task 298267721 298267768 ]
> > > [ thread-roots-task 298267769 298267783 ]
> > > [ thread-roots-task 298267801 298267812 ]
> > > [ thread-roots-task 298267814 298267819 ]
> > > [ thread-roots-task 298267821 298267825 ]
> > > [ scavenge-roots-task 298267826 298267924 ]
> > > [ steal-task 298267925 298296466 ]
> > > GC-Thread 3 entries: 11
> > > [ thread-roots-task 298267634 298267653 ]
> > > [ thread-roots-task 298267659 298267680 ]
> > > [ thread-roots-task 298267682 298267690 ]
> > > [ thread-roots-task 298267692 298267725 ]
> > > [ thread-roots-task 298267726 298267733 ]
> > > [ thread-roots-task 298267735 298267741 ]
> > > [ thread-roots-task 298267746 298267775 ]
> > > [ thread-roots-task 298267776 298267787 ]
> > > [ thread-roots-task 298267790 298267805 ]
> > > [ thread-roots-task 298267807 298267813 ]
> > > [ steal-task 298267848 298296340 ]
> > > GC-Thread 4 entries: 13
> > > [ old-to-young-roots-task 298267561 298267611 ]
> > > [ scavenge-roots-task 298267613 298267639 ]
> > > [ thread-roots-task 298267640 298267661 ]
> > > [ thread-roots-task 298267664 298267673 ]
> > > [ thread-roots-task 298267675 298267685 ]
> > > [ thread-roots-task 298267687 298267696 ]
> > > [ thread-roots-task 298267699 298267707 ]
> > > [ thread-roots-task 298267708 298267717 ]
> > > [ thread-roots-task 298267725 298267765 ]
> > > [ thread-roots-task 298267767 298267781 ]
> > > [ thread-roots-task 298267807 298267828 ]
> > > [ scavenge-roots-task 298267829 298267831 ]
> > > [ steal-task 298267833 298296387 ]
> > > GC-Thread 5 entries: 13
> > > [ old-to-young-roots-task 298267573 298267618 ]
> > > [ thread-roots-task 298267622 298267651 ]
> > > [ thread-roots-task 298267654 298267661 ]
> > > [ thread-roots-task 298267663 298267669 ]
> > > [ thread-roots-task 298267670 298267696 ]
> > > [ thread-roots-task 298267698 298267704 ]
> > > [ thread-roots-task 298267706 298267712 ]
> > > [ thread-roots-task 298267719 298267726 ]
> > > [ thread-roots-task 298267727 298267781 ]
> > > [ thread-roots-task 298267784 298267791 ]
> > > [ thread-roots-task 298267792 298267821 ]
> > > [ scavenge-roots-task 298267823 298269583 ]
> > > [ steal-task 298269584 298296338 ]
> > > GC-Thread 6 entries: 11
> > > [ old-to-young-roots-task 298267551 298267601 ]
> > > [ serial-old-to-young-roots-task 298267603 298267625 ]
> > > [ thread-roots-task 298267626 298267653 ]
> > > [ thread-roots-task 298267666 298267676 ]
> > > [ thread-roots-task 298267678 298267684 ]
> > > [ thread-roots-task 298267686 298267691 ]
> > > [ thread-roots-task 298267692 298267723 ]
> > > [ thread-roots-task 298267725 298267730 ]
> > > [ thread-roots-task 298267789 298267803 ]
> > > [ thread-roots-task 298267804 298267818 ]
> > > [ steal-task 298267863 298296447 ]
> > > GC-Thread 7 entries: 8
> > > [ old-to-young-roots-task 298267603 298267648 ]
> > > [ thread-roots-task 298267650 298267687 ]
> > > [ thread-roots-task 298267689 298267731 ]
> > > [ thread-roots-task 298267773 298267786 ]
> > > [ thread-roots-task 298267788 298267793 ]
> > > [ thread-roots-task 298267797 298267855 ]
> > > [ steal-task 298267857 298296336 ]
> > > [ waitfor-barrier-task 298296341 298296578 ]
> > > GC-Thread 8 entries: 9
> > > [ old-to-young-roots-task 298267594 298267634 ]
> > > [ thread-roots-task 298267637 298267674 ]
> > > [ thread-roots-task 298267675 298267712 ]
> > > [ thread-roots-task 298267716 298267732 ]
> > > [ thread-roots-task 298267760 298267768 ]
> > > [ thread-roots-task 298267816 298267824 ]
> > > [ scavenge-roots-task 298267826 298267828 ]
> > > [ scavenge-roots-task 298267829 298267831 ]
> > > [ steal-task 298267832 298296428 ]
> > > GC-Thread 9 entries: 17
> > > [ old-to-young-roots-task 298267540 298267584 ]
> > > [ old-to-young-roots-task 298267586 298267628 ]
> > > [ thread-roots-task 298267629 298267652 ]
> > > [ thread-roots-task 298267656 298267666 ]
> > > [ thread-roots-task 298267667 298267676 ]
> > > [ thread-roots-task 298267677 298267694 ]
> > > [ thread-roots-task 298267698 298267708 ]
> > > [ thread-roots-task 298267709 298267715 ]
> > > [ thread-roots-task 298267744 298267754 ]
> > > [ thread-roots-task 298267756 298267763 ]
> > > [ thread-roots-task 298267765 298267775 ]
> > > [ thread-roots-task 298267778 298267801 ]
> > > [ thread-roots-task 298267802 298267809 ]
> > > [ thread-roots-task 298267810 298267812 ]
> > > [ thread-roots-task 298267817 298267823 ]
> > > [ scavenge-roots-task 298267825 298267830 ]
> > > [ steal-task 298267832 298296460 ]
> > > GC-Thread 10 entries: 12
> > > [ scavenge-roots-task 298267613 298267618 ]
> > > [ thread-roots-task 298267621 298267638 ]
> > > [ thread-roots-task 298267639 298267659 ]
> > > [ thread-roots-task 298267663 298267671 ]
> > > [ thread-roots-task 298267673 298267682 ]
> > > [ thread-roots-task 298267683 298267693 ]
> > > [ thread-roots-task 298267695 298267705 ]
> > > [ thread-roots-task 298267707 298267720 ]
> > > [ thread-roots-task 298267723 298267730 ]
> > > [ thread-roots-task 298267795 298267811 ]
> > > [ thread-roots-task 298267813 298267833 ]
> > > [ steal-task 298267834 298296472 ]
> > > GC-Thread 11 entries: 13
> > > [ old-to-young-roots-task 298267514 298267589 ]
> > > [ old-to-young-roots-task 298267592 298267657 ]
> > > [ thread-roots-task 298267660 298267674 ]
> > > [ thread-roots-task 298267677 298267693 ]
> > > [ thread-roots-task 298267694 298267702 ]
> > > [ thread-roots-task 298267706 298267716 ]
> > > [ thread-roots-task 298267721 298267731 ]
> > > [ thread-roots-task 298267735 298267744 ]
> > > [ thread-roots-task 298267746 298267753 ]
> > > [ thread-roots-task 298267757 298267786 ]
> > > [ thread-roots-task 298267789 298267799 ]
> > > [ thread-roots-task 298267802 298267814 ]
> > > [ steal-task 298267838 298296336 ]
> > > GC-Thread 12 entries: 15
> > > [ old-to-young-roots-task 298267499 298267597 ]
> > > [ thread-roots-task 298267636 298267652 ]
> > > [ thread-roots-task 298267654 298267686 ]
> > > [ thread-roots-task 298267688 298267698 ]
> > > [ thread-roots-task 298267701 298267710 ]
> > > [ thread-roots-task 298267711 298267720 ]
> > > [ thread-roots-task 298267723 298267730 ]
> > > [ thread-roots-task 298267731 298267740 ]
> > > [ thread-roots-task 298267743 298267755 ]
> > > [ thread-roots-task 298267757 298267770 ]
> > > [ thread-roots-task 298267772 298267783 ]
> > > [ thread-roots-task 298267786 298267796 ]
> > > [ thread-roots-task 298267798 298267805 ]
> > > [ thread-roots-task 298267811 298267813 ]
> > > [ steal-task 298267843 298296347 ]
> 
> 
> 
> -- 
> =============================
> | BlueDavy |
> | http://www.bluedavy.com |
> =============================




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