Java Concurrent Marking; Related Publications - IBM Power7 Optimization And Tuning Manual

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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<

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<

default, one thread is used for concurrent marking.

For more information about this topic, see 7.6, "Related publications" on page 136.

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

136

POWER7 and POWER7+ Optimization and Tuning Guide

number

> option, which specifies the ratio between the

number

> option. By

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