Where have the Full GCs gone?

[Moazam Raja]

Peter, you were right, once again. :)

Indeed, the heap is set to 20GB. Not what I had expected!

Thanks!


-Moazam

> ----- Original Message -----
> From: Moazam Raja <moazam at apple.com>
> Date: Tuesday, November 4, 2008 5:04 pm
> Subject: Re: Where have the Full GCs gone?
> To: "Peter B. Kessler" <Peter.Kessler at Sun.COM>
> Cc: hotspot-gc-use at openjdk.java.net
>
>
>> Peter, this must be a bug in the GC output as I know for sure I don't
>>
>> have the memory to run a 20GB heap.
>>
>> Instead of 20950272K, it must mean 20950272Kb.
>>
>> This is on Java 1.5.0 on OS X Leopard.
>>
>> java version "1.5.0_13"
>> Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_13-
>> b05-237)
>> Java HotSpot(TM) Server VM (build 1.5.0_13-119, mixed mode)
>>
>>
>> -Moazam
>>
>> On Nov 4, 2008, at 4:52 PM, Peter B. Kessler wrote:
>>
>>> Moazam Raja wrote:
>>>> Hi all, I'm running a test and recording GC information on a
>>>> Tomcat  application and have noticed that even after a few days,
>>>> there are no  'Full GC' markers. Am I reading the log incorrectly,
>>
>>>> or are the Full  GCs getting logged elsewhere?
>>>> I'm using Java 1.5.0_13 on OS X with the following flags,
>>>>        -Xms=2048m -Xmx=2048m
>>>>        -server -XX:+UseConcMarkSweepGC
>>>>        -Xloggc:/var/tmp/GC.log
>>>>        -verbose:gc
>>>>        -XX:+PrintGCDetails
>>>>        -XX:+PrintHeapAtGC
>>>>        -XX:+PrintClassHistogram
>>>>        -XX:+PrintGCApplicationConcurrentTime
>>>> A sample of the output from my GC log:
>>>> Application time: 1.4105823 seconds
>>>> 82558.187: [GC {Heap before gc invocations=111716:
>>>> par new generation   total 21184K, used 21120K
>>>> [0x0000000107270000, 0x0000000108730000, 0x0000000108730000)
>>>>  eden space 21120K, 100% used [0x0000000107270000,
>>>> 0x0000000108710000, 0x0000000108710000)
>>>>  from space 64K,   0% used [0x0000000108710000,
>>>> 0x0000000108710000, 0x0000000108720000)
>>>>  to   space 64K,   0% used [0x0000000108720000,
>>>> 0x0000000108720000, 0x0000000108730000)
>>>> concurrent mark-sweep generation total 20950272K, used 5483440K
>>>> [0x0000000108730000, 0x0000000607270000, 0x0000000607270000)
>>>> concurrent-mark-sweep perm gen total 39296K, used 23575K
>>>> [0x0000000607270000, 0x00000006098d0000, 0x000000060c670000)
>>>> 82558.187: [ParNew: 21120K->0K(21184K), 0.0669633 secs] 5504560K-
>>>>> 5487545K(20971456K)Heap after gc invocations=111717:
>>>> par new generation   total 21184K, used 0K [0x0000000107270000,
>>>> 0x0000000108730000, 0x0000000108730000)
>>>>  eden space 21120K,   0% used [0x0000000107270000,
>>>> 0x0000000107270000, 0x0000000108710000)
>>>>  from space 64K,   0% used [0x0000000108720000,
>>>> 0x0000000108720000, 0x0000000108730000)
>>>>  to   space 64K,   0% used [0x0000000108710000,
>>>> 0x0000000108710000, 0x0000000108720000)
>>>> concurrent mark-sweep generation total 20950272K, used 5487545K
>>>> [0x0000000108730000, 0x0000000607270000, 0x0000000607270000)
>>>> concurrent-mark-sweep perm gen total 39296K, used 23575K
>>>> [0x0000000607270000, 0x00000006098d0000, 0x000000060c670000)
>>>> }
>>>> , 0.0672098 secs]
>>>> ...
>>>
>>> I don't think those are the command line arguments for the GC log
>>> you show.  It looks from the PrintHeapAtGG output that your heap is
>>
>>> 20GB, not the 2GB shown on the command line.  20MB in the "par new"
>>
>>> generation, and the reast of the 20GB in the CMS generation.
>>>
>>> It looks like you are using just over 5GB of CMS space, which would
>>
>>> explain why you haven't seen an old generation collection yet.
>>>
>>>                	... peter
>>
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