[10] RFR(S): 8087339: The code heap might use different alignment for committed size and reserved size

[Tobias Hartmann]

Hi Vladimir,

thanks for the review!

Best regards,
Tobias

On 22.11.2017 21:23, Vladimir Kozlov wrote:
> Good.
> 
> Thanks,
> Vladimir
> 
> On 11/22/17 5:51 AM, Tobias Hartmann wrote:
>> Hi,
>>
>> please review the following patch:
>> https://bugs.openjdk.java.net/browse/JDK-8087339
>> http://cr.openjdk.java.net/~thartmann/8087339/webrev.00/
>>
>> The alignment of the code cache is determined in CodeCache::reserve_heap_memory() by computing the minimum of the page
>> size for the ReservedCodeCacheSize and the InitialCodeCacheSize (which is usually very small and not aligned to the
>> large page size). As a result, when using large pages (by enabling UseTransparentHugePages or UseHugeTLBFS), the
>> ReservedSpace is only backed by large pages if the InitialCodeCacheSize is large page aligned as well.
>>
>> I've changed the implementation to not consider InitialCodeCacheSize and re-factored the code to use
>> CodeCache::page_size() both for the alignment of heap sizes as well as the alignment of the entire reserved space.
>>
>> I've verified that this sets the correct alignment on my machine when using 2048K pages instead of 4K pages.
>>
>> Thanks,
>> Tobias
>>