CODEWITHSUNDEEP
javajvmperformance-testingjvm-argumentsjvm-hotspot
Sanjay
Sanjay

Reputation: 1108

How young-generation size will be resized?

I was trying to understand different parameters used to define JVM Heap size.

    <jdkarg value="-Xmx20000M"/>
    <jdkarg value="-Xms10000M"/>
    <jdkarg value="-XX:NewSize=2500M"/>
    <jdkarg value="-XX:NewRatio=1"/>
    <jdkarg value="-XX:MaxNewSize=5000"/>

Here I know what is the meaning of these jdkarg, what is making me to confused, I read somewhere that if I define -XX:NewSize and -XX:NewRatio both then while stating jvm will allocate young generation size using -XX:NewSize not -XX:NewRatio.

So here I have some questions regarding this:

I tried a lot of googling but not found any conclusion. Any help to understand these arg together will be appreciated.

Update:

output I am getting is not as expected:

 S0C       S1C      S0U     S1U      EC       EU        OC         OU         PC       PU       YGC    YGCT   FGC      FGCT    GCT
426624.0 426624.0  0.0   426624.0 1706752.0 1013097.7 17920000.0 7208855.8  137032.0 82118.0   1952  130.126  24     20.441  150.567

Here I am getting Old space as 17920000 i.e. 17500 MB and young space as 2500 MB which was my initial value.

Upvotes: 2

Views: 4724

Answers (2)

Oleksandr Pyrohov
Oleksandr Pyrohov

Reputation: 16226

When we define -XX:NewSize and -XX:NewRatio then initial young generation size will be defined using -XX:NewSize, is it correct?

NewRatio is ignored if it is used together with NewSize and MaxNewSize

What happens when Heap size increase to it's MAX in this case 20000M, then how it define max young generation size, will it use -MaxNewSize or -XX:NewRatio or none of them will be used as I have -XX:NewSize?

When both NewSize and MaxNewSize are used, young generation will be between those 2 sizes. But when heap size change, the young generation size will not change accordingly.

Original source

Upvotes: 2

Sanjay
Sanjay

Reputation: 1108

Here I am pointing out the problem so that similar thing can be noticed before going further which was causing this behaviors :

Ideally this should be behaviors as mention by @Oleksandr:

Both -XX:NewSize and -XX:MaxNewSize are used, young gen will be between those 2 sizes. But when heap size change, the young gen size will not change accordingly.

but because I have <jdkarg value="-XX:MaxNewSize=5000"/> that means 5000 Bytes that means it is never going to increase Young Space up to MaxNewSize as NewSize is already greater then, correct way of setting it's max value <jdkarg value="-XX:MaxNewSize=5000M"/>.

When I made this changes i.e. added defined size as MB then it is giving memory distribution as expected.

Upvotes: 1

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