InlineCacheBuffer question

[Roman Kennke]

Hi Tony,


>> > I’m not familiar with the InlineCacheBuffer at all. How important is it
>> > to execute InlineCacheBuffer::update_inline_caches() at regular
>> > intervals? Would a modified heuristic, like "a safepoint is required if
>> > the buffer is >P% full" (maybe in conjunction with increasing the buffer
>> > size) be reasonable? Or maybe increase the value of
>> > GuaranteedSafepointInterval? Or both?
>>
>> I think such a modified heuristic would be reasonable.
>>
>> > Note that the overhead of the non-VM op safepoints is actually
>> > negligible. I’d just like to try to cut down the number of safepoints we
>> > do, as we had issues in the past with safepoint initiation taking too long.
>> >
>>
>> I can feel your pain.
> 
> 
> I’m all for decreasing the overhead of the various cleanups that are 
> done pre-safepoint (and thanks for the pointers). But, I’m also 
> interested in just decreasing the number of safepoints that we do, if 
> they are not absolutely necessary.

I agree it would be useful to extend the heuristics to do something 
similar to what ObjectSynchronizer::is_cleanup_needed() does: check 
actual usage of InlineCacheBuffer, and compare it to a threshold, and 
let the threshold be configurable via cmd line option.

Roman