[12] RFR: 8208499 NMT: Missing memory tag for Safepoint polling page

Zhengyu Gu zgu at redhat.com
Mon Jul 30 15:34:26 UTC 2018



On 07/30/2018 11:20 AM, Zhengyu Gu wrote:
> Thanks for the quick review.
> 
> On 07/30/2018 11:05 AM, Aleksey Shipilev wrote:
>> On 07/30/2018 04:58 PM, Zhengyu Gu wrote:
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8208499
>>> Webrev: http://cr.openjdk.java.net/~zgu/8208499/webrev.00/index.html
>>
>> *) memory/allocation.hpp, is it really necessary to drop values from 
>> enum?
> 
> The values are unnecessary. Every time we add a new tag, we have to 
> shift/update values, which is inconvenience and might introduce bugs.
> 
>>
>> *) services/memTracker.cpp, not sure why you need to assert this:
>>
>>    54   // memory type occupies a byte
>>    55   STATIC_ASSERT(mt_number_of_types <= max_jubyte);
> 
> memory type is encoded into tracking header as a byte field. The 
> assertion ensures that we don't introduce more types that can overflow a 
> byte.

Updated comment to clarify the assertion.

Thanks,

-Zhengyu

> 
>>
>> *) runtime/NMT/SafepointPollingPages.java, excess newline:
>>
>>    48
>>    49
> 
> Fixed.
> 
> http://cr.openjdk.java.net/~zgu/8208499/webrev.01/
> 
> -Zhengyu
> 
>>
>> Otherwise looks good.
>>
>> -Aleksey
>>


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