Trace object type in GC

[Krystal Mok]

That's great to hear!

Thanks,
Kris

On Fri, Sep 14, 2012 at 12:42 AM, Sam Pullara <spullara at twitter.com> wrote:

> Good news. The patch has been coerced to be in line with hotspot
> development practices and we are going to try and upstream it.
>
> Sam
>
>
> On Sat, Jun 30, 2012 at 12:46 PM, Sam Pullara <spullara at twitter.com>wrote:
>
>> I can post a patch here, but it is currently dependent on the STL. The
>> facilities for this within Hotspot's libraries are pretty poor. I attempted
>> a port to libadt but ran into a bunch of issues. It is a pretty small
>> amount of code if someone wants to volunteer to put it into shape for
>> upstreaming it.
>>
>> Sam
>>
>> On Jun 11, 2012, at 9:10 PM, Krystal Mok wrote:
>>
>> Hi San,
>>
>> Wow, that's nice.
>> Is there any plans to submit it to hotspot-gc-dev as a patch to OpenJDK?
>>
>> - Kris
>>
>> On Tue, Jun 12, 2012 at 12:06 PM, Sam Pullara <spullara at twitter.com>wrote:
>>
>>> What we would really like to have is a GC option that prints the top-N
>>> class histogram only for those that are being migrated from the oldest
>>> tenure age into the old generation. I have a prototype of it and it works,
>>> but it would be great if it was in the main code line.
>>>
>>> Sam
>>>
>>> On Jun 11, 2012, at 8:34 PM, Krystal Mok wrote:
>>>
>>> Hi Nicolas,
>>>
>>> If you're interested in the objects collected on a type-granularity,
>>> then the following VM arguments gets close:
>>>
>>> manageable(bool, PrintClassHistogramBeforeFullGC, false,          \
>>>         "Print a class histogram before any major stop-world GC") \
>>>                                                                   \
>>> manageable(bool, PrintClassHistogramAfterFullGC, false,           \
>>>         "Print a class histogram after any major stop-world GC")  \
>>>
>>> What they do is basically the same as running jmap -histo before or
>>> after a full GC, printing the histogram of objects grouped by class.
>>> Comparing the numbers before and after a full GC will give you the idea of
>>> what's collected in that full GC.
>>>
>>> You can turn these flags on by specifying them in the VM command line
>>> arguments, e.g. -XX:+PrintClassHistogramBeforeFullGC
>>> Or you could change their values while the VM is running, e.g. jinfo
>>> -flag +PrintClassHistogramBeforeFullGC <pid>
>>>
>>> (There's no equivalent flag for minor GCs in HotSpot.)
>>>
>>> If you're looking for information on a object-granularity, then it's
>>> something HotSpot VM doesn't support. GC implementations seldom track such
>>> information.
>>>
>>> Hope it helps,
>>> - Kris
>>>
>>> On Mon, Jun 11, 2012 at 11:36 PM, RICHARD Nicolas <
>>> nicolas.richard at atos.net> wrote:
>>>
>>>>  Dear hotspot developper,
>>>> I currently develop applications in Java.
>>>>
>>>> I am looking for a way to trace objects freed by the Garbage Collector.
>>>> For the time being, I've only found options to get statistics about GC
>>>> (execution time, average amount of freed memory, etc) but no one about the
>>>> type of object handled by the GC.
>>>>
>>>> Is there any option that I could use or is it possible to develop a JVM
>>>> TI agent to get this information ?
>>>>
>>>> Best regards
>>>> Nicolas RICHARD
>>>>
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