MinHeapFreeRatio / MaxHeapFreeRatio

[Damon Hart-Davis]

Hi,

Thanks, so:

% java -fullversion
java full version "1.8.0-b132"

Should be fine if I give it a whirl somehow then!

Rgds

Damon

On 30 Jun 2014, at 16:28, Damon Hart-Davis <dhd at exnet.com> wrote:

> Hi Jon,
> 
> Did CMS get fixed to observe -XX:MaxHeapFreeRatio in JDK8?
> 
> Rgds
> 
> Damon
> 
>> 
>> On 5/8/2012 11:47 PM, Damon Hart-Davis wrote:
>>> Hi,
>>> 
>>> Note: I should have been clear that memory is not given back to the OS even when the heap is (say) 60%+ free and I force GCs.
>>> 
>>> Rgds
>>> 
>>> Damon
>>> 
>>> 
>>> On 9 May 2012, at 06:46, Damon Hart-Davis wrote:
>>> 
>>>> Hi,
>>>> 
>>>> First time on this list, so hello!  I see a few familiar names from days of yore!
>>>> 
>>>> I am running my favourite (Tomcat/Web) app in a very constrained memory environment (a SheevaPlug) along with all the usual Internet server junk (sendmail,  ntp, sshd, etc) and I am aiming to squeeze it into the even tighter space of a Raspberry Pi in due course.
>>>> 
>>>> As such, I want the JVM to give memory back to the OS whenever possible.  In code I set a target to keep about 25% of the heap free, and so for example I stop cacheing some stuff when below that, and cache more vigorously above that.
>>>> 
>>>> Here are some relevant options:
>>>> 
>>>> CATALINA_OPTS="-Xmx100m -Xms64m"
>>>> # Cap size of non-(main-)heap components.
>>>> CATALINA_OPTS="$CATALINA_OPTS -XX:MaxPermSize=48m"
>>>> # Trim thread stack size.
>>>> CATALINA_OPTS="$CATALINA_OPTS -Xss256k"
>>>> # Keep the new generation well within the target 25% free...
>>>> CATALINA_OPTS="$CATALINA_OPTS -XX:NewRatio=5"
>>>> # Be aggressive about giving memory back to the system above target 25% free.
>>>> CATALINA_OPTS="$CATALINA_OPTS -XX:MinHeapFreeRatio=10 -XX:MaxHeapFreeRatio=26"
>>>> # Run in incremental GC mode to minimise pauses.
>>>> CATALINA_OPTS="$CATALINA_OPTS -Xincgc"
>>>> 
>>>> I see some evidence that the free ratios are being observed by when the heap is expanded, but I have never seen any variant of JDK 6 or 7, including the Oracle embedded 6, actually give memory back to the OS with this app.
>>>> 
>>>> Am I still doing something wrong?  B^>
>>>> 
>>>> Rgds
>>>> 
>>>> Damon
>>>> 
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