RFR: 7169803: Usage of pretenured value is not correct

Tao Mao yiyeguhu at gmail.com
Thu Jun 11 07:47:37 UTC 2015


Hi Jon,

The definition is: "Promoted" is objects that are promoted (or tenured)
during yGC while "PRE-tenured" is objects that are allocated directly in
old gen. I believe this is so, right?

Thanks.
Tao Mao



On Wed, Jun 10, 2015 at 6:48 PM, Jon Masamitsu <jon.masamitsu at oracle.com>
wrote:

>
>
> On 6/10/2015 5:51 PM, Tao Mao wrote:
>
> I think David's right. Promoted objects and pretenured objects are
> different guys. This would resolve the second issue in the ticket
> JDK-7169803.
>
>
> Tao,
>
> How would you define each?
>
> Jon
>
>
>
>  Thanks.
> Tao Mao
>
> On Wed, Jun 10, 2015 at 5:08 PM, Jon Masamitsu <jon.masamitsu at oracle.com>
> wrote:
>
>>
>>
>> On 6/10/2015 1:30 AM, David Lindholm wrote:
>>
>>> Jon,
>>>
>>> Thanks for taking a look at this. No, I don't think this will lead to
>>> double counting. This calculation is already there, it is just buggy.
>>> Before this patch the code added the total amount of promoted memory this
>>> collection with the average size of the pretenured objects, and used this
>>> as a sample. Now the code adds the total amount of promoted memory with the
>>> total size of the pretenured objects since last collection, and uses this
>>> as a sample instead.
>>>
>>
>>  Aren't "promoted" and "total_pretenured_since_last_promotion()"
>> approximately the same
>> thing?  In share/vm/gc/parallel/psScavenge.cpp
>>
>> 489       size_t promoted = old_gen->used_in_bytes() -
>> old_gen_used_before;
>> 490       size_policy->update_averages(_survivor_overflow, survived,
>> promoted);
>>
>> so "promoted" is the change in the old gen between the before and after
>> the
>> young gen collection.
>>
>> "total_pretenured_size_last_promotion()" is
>>
>>  258   void tenured_allocation(size_t size) {
>>  259     _avg_pretenured->sample(size);
>>  260     add_pretenured_since_last_promotion(size)
>>
>>
>> which seems to me to be calculating the same thing (sum of allocations
>> into the old gen).
>>
>> Not so?
>>
>> Jon
>>
>>
>>
>>>
>>> Thanks,
>>> David
>>>
>>> On 2015-06-09 21:37, Jon Masamitsu wrote:
>>>
>>>> David,
>>>>
>>>>
>>>> http://cr.openjdk.java.net/~david/JDK-7169803/webrev.00/src/share/vm/gc/parallel/psAdaptiveSizePolicy.cpp.frames.html
>>>>
>>>> 1308   avg_promoted()->sample(promoted +
>>>> total_pretenured_since_last_promotion());
>>>>
>>>>
>>>> Is including both "promoted" and
>>>> "total_pretenured_since_last_promotion()"
>>>> double counting?
>>>>
>>>> Jon
>>>>
>>>> On 06/09/2015 02:06 AM, David Lindholm wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> Please review this patch that corrects the usage of the pretenured
>>>>> value. There were 2 issues: words and bytes were mixed up and the addition
>>>>> was done with the wrong value. See bug for details.
>>>>>
>>>>> Webrev: http://cr.openjdk.java.net/~david/JDK-7169803/webrev.00/
>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-7169803
>>>>>
>>>>>
>>>>> Testing: Passed JPRT
>>>>>
>>>>>
>>>>> Thanks,
>>>>> David
>>>>>
>>>>
>>>>
>>>
>>
>
>
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