136 POWER7 and POWER7+ Optimization and Tuning Guide
7.5.5 Java concurrent marking
The gencon policy combines concurrent marking with generational GC. If generational GC is
wanted but the impact of concurrent marking, regarding both the impact of the marking thread
and the extra book-keeping that is required when you allocate and manipulate objects, is not
wanted, then concurrent marking can be disabled by using the -Xconcurrentlevel0 option.
This option is appropriate for workloads that benefit from the gencon policy for object
allocation and lifetimes, but also require maximum throughput and minimal GC impact while
the application threads are running.
In general, for both the gencon and optavgpause GC policies, concurrent marking can be
tuned with the -Xconcurrentlevel<
number> option, which specifies the ratio between the
amounts of heap that is allocated and heap marked. The default value is 8. The number of
low priority mark threads can be set with the -Xconcurrentbackground<
number> option. By
default, one thread is used for concurrent marking.
For more information about this topic, see 7.6, “Related publications” on page 136.
7.6 Related publications
The publications that are listed in this section are considered suitable for a more detailed
discussion of the topics that are covered in this chapter:
Java performance for AIX on POWER7 – best practices, found at:
https://www-304.ibm.com/partnerworld/wps/servlet/ContentHandler/stg_ast_sys_jav
a_performance_on_power7
Java Performance on POWER7, found at:
https://www.ibm.com/developerworks/wikis/display/LinuxP/Java+Performance+on+POW
ER7
Top 10 64-bit IBM WebSphere Application Server FAQ, found at:
ftp://public.dhe.ibm.com/software/webservers/appserv/WAS_64-bit_FAQ.pdf
To Next Page
Loading...
