G1 GC Humongous Objects - Garbage collection

[Gopal, Prasanna CWK]

Hi Thomas 

Thanks for your explanation. Appreciate your help.

Thanks and Regards
Prasanna 

-----Original Message-----
From: Thomas Schatzl [mailto:thomas.schatzl at oracle.com] 
Sent: 25 October 2016 10:24
To: Gopal, Prasanna CWK <prasanna.gopal at blackrock.com>; hotspot-gc-use at openjdk.java.net
Subject: Re: G1 GC Humongous Objects - Garbage collection

Hi,

On Tue, 2016-10-25 at 08:41 +0000, Gopal, Prasanna CWK wrote:
> Hi All
>  
> I have the following question about Garbage collection of  Humongous 
> objects.
>  
> 1)     When will the humongous objects will get reclaimed ?
> 2)     Is there is any behaviour difference between Jdk 7 and Jdk 8 
> run time ?
> 3)     I understand, in pre-jdk 8 G1 GC , the humongous objects gets 
> collected only through Full GC. In my application , I couldn’t see 
> Full GC happening for long time (running on jdk_7u40_x64) , does this 
> means the humongous objects stay in memory , till we have a full GC ?

G1 can reclaim humongous objects...

* at the end of marking in the GC Cleanup pause.

* during full gc.

* JDK8u60+ can also reclaim particular types of humongous objects (arrays that do _not_ consist of references to objects) at every young GC. See the release notes for 8u60 at https://urldefense.proofpoint.com/v2/url?u=http-3A__www.oracle.com_technetwork&d=DQIFaQ&c=zUO0BtkCe66yJvAZ4cAvZg&r=zRhnqN6xuCQh8NZ-MtoiYBMlItU6r8UBO9AjZ3c3DEY&m=5pQkGSufUB_aL1XJUcW86zVuBn5xYh1XrUD5N2zcu1M&s=OKbYPqGNR3NGiLzOFh6tXk2cXLnbhFxrp8H4Svff20A&e=
/java/javase/8u60-relnotes-2620227.html under "New Features and Changes" for how to control this.
(It works for any array of primitive type, not limited to the examples given there - just in case you wonder).

Thanks,
  Thomas



This message may contain information that is confidential or privileged. If you are not the intended recipient, please advise the sender immediately and delete this message. See http://www.blackrock.com/corporate/en-us/compliance/email-disclaimers for further information.  Please refer to http://www.blackrock.com/corporate/en-us/compliance/privacy-policy for more information about BlackRock’s Privacy Policy.
BlackRock Advisors (UK) Limited and BlackRock Investment Management (UK) Limited are authorised and regulated by the Financial Conduct Authority. Registered in England No. 796793 and No. 2020394 respectively. BlackRock Life Limited is authorised by the Prudential Regulation Authority and regulated by the Financial Conduct Authority and the Prudential Regulation Authority. Registered in England No. 2223202. Registered Offices: 12 Throgmorton Avenue, London EC2N 2DL. BlackRock International Limited is authorised and regulated by the Financial Conduct Authority and is a registered investment adviser with the Securities and Exchange Commission (SEC). Registered in Scotland No. SC160821. Registered Office: Exchange Place One, 1 Semple Street, Edinburgh EH3 8BL.


For a list of BlackRock's office addresses worldwide, see http://www.blackrock.com/corporate/en-us/about-us/contacts-locations.

© 2016 BlackRock, Inc. All rights reserved.