RFR (S) Allow ResourceHashtable size to be specified at runtime

[Jiangli Zhou]

Hi Ioi,

On 11/14/18 9:09 AM, Ioi Lam wrote:
>
>
> On 11/13/18 4:05 PM, Jiangli Zhou wrote:
>> Hi Ioi,
>>
>> The change looks reasonable to me in general. It would be helpful to 
>> see the performance difference with the expendable table. Do you have 
>> any data when large number of classes are loaded (>20000)? How much 
>> saving does it provide?
>>
>
> Hi Jiangli, thanks for the review. For dumping 30292 classes:
>
> BEFORE: 93.971 sec
> AFTER:  34.761 sec

Thanks for the data! That's about 2.6x improvement with large set of 
classes.

Thanks,
Jiangli
>
> Thanks
> - Ioi
>
>> Thanks,
>>
>> Jiangli
>>
>>
>> On 11/8/18 10:35 PM, Ioi Lam wrote:
>>> https://bugs.openjdk.java.net/browse/JDK-8213587
>>> http://cr.openjdk.java.net/~iklam/jdk12/8213587-configurable-resource-hash.v01/ 
>>>
>>>
>>> TL;DR: -- add a subclass to ResourceHashtable to allow the table 
>>> size to be
>>>           dynamically specified when the table is constructed.
>>>
>>>
>>>         *** C++ template guru alert ***
>>>
>>>
>>> I don't know much about C++ templates, so my attempt on doing this 
>>> may be
>>> ill-advised.
>>>
>>> I *think* that with my patch, the performance of existing code, 
>>> which uses
>>> a statically-defined SIZE,  should not be affected, as the C++ compiler
>>> should be able to constant-propagate and reduce the new code:
>>>
>>>   ALWAYSINLINE unsigned size() const {
>>>     if (SIZE != CONFIGURABLE_SIZE) {
>>>       return SIZE;
>>>     } else {
>>>       return _configured_table_size;
>>>     }
>>>   }
>>>
>>>   ALWAYSINLINE Node** get_table() const {
>>>     if (SIZE != CONFIGURABLE_SIZE) {
>>>       return (Node**)(&_static_table[0]);
>>>     } else {
>>>       return _configured_table;
>>>     }
>>>   }
>>>
>>>   Node** lookup_node(unsigned hash, K const& key) {
>>>     unsigned index = hash % size();    <-----
>>>     Node** table = get_table();
>>>     Node** ptr = &table[index];   <-----
>>>
>>> back to the old code:
>>>
>>>   Node** lookup_node(unsigned hash, K const& key) {
>>>     unsigned index = hash % SIZE;      <-----
>>>     Node** ptr = &_table[index];       <-----
>>>
>>>
>>> If anyone has a better way of doing this, I'd love to hear it!
>>>
>>> Thanks!
>>> - Ioi
>>>
>>>
>>>
>>>
>>
>