RFR(L): 8195098: Low latency hashtable for read-mostly scenarios

[Gerard Ziemski]

hi Robbin,

There are 2 minor issues that caught my eye, anything else we can fix in followup issues:

#1 

 // This method looks on the _invisible_epoch field and
 // does a write_synchronize if needed.
 void write_synchonize_on_visible_epoch(Thread* thread);


a) I think in the word “looks” in the comment should be “locks”
b) Why is the method name using word “visible” when it locks on an “invisible” epoch?


#2 ScopedCS and MultiGetHandle look identical?

// ScopedCS
template <typename VALUE, typename CONFIG, MEMFLAGS F>
inline ConcurrentHashTable<VALUE, CONFIG, F>::
 ScopedCS::ScopedCS(Thread* thread, ConcurrentHashTable<VALUE, CONFIG, F>* cht)
   : _thread(thread), _cht(cht)
{
 GlobalCounter::critical_section_begin(_thread);
 // This version is published now.
 if (OrderAccess::load_acquire(&_cht->_invisible_epoch) != NULL) {
   OrderAccess::release_store_fence(&_cht->_invisible_epoch, (Thread*)NULL);
 }
}

template <typename VALUE, typename CONFIG, MEMFLAGS F>
inline ConcurrentHashTable<VALUE, CONFIG, F>::
 ScopedCS::~ScopedCS()
{
 GlobalCounter::critical_section_end(_thread);
}

// MultiGetHandle
template <typename VALUE, typename CONFIG, MEMFLAGS F>
inline ConcurrentHashTable<VALUE, CONFIG, F>::
 MultiGetHandle::MultiGetHandle(Thread* thread,
                                ConcurrentHashTable<VALUE, CONFIG, F>* cht)
   : _thread(thread), _cht(cht)
{
 GlobalCounter::critical_section_begin(_thread);
 // This version is published now.
 if (OrderAccess::load_acquire(&_cht->_invisible_epoch) != NULL) {
   OrderAccess::release_store_fence(&_cht->_invisible_epoch, (Thread*)NULL);
 }
}

template <typename VALUE, typename CONFIG, MEMFLAGS F>
inline ConcurrentHashTable<VALUE, CONFIG, F>::
 MultiGetHandle::~MultiGetHandle()
{
 GlobalCounter::critical_section_end(_thread);
}


cheers

> On May 2, 2018, at 4:03 AM, Robbin Ehn <robbin.ehn at oracle.com> wrote:
> 
> Hi all,
> 
> Here is an update with Gerard's and Coleen's input.
> 
> Inc:
> http://cr.openjdk.java.net/~rehn/8195098/v1/inc/webrev/
> Full:
> http://cr.openjdk.java.net/~rehn/8195098/v1/full/webrev/
> 
> Thanks, Robbin