[10] RFR: 8179040: Avoid Ticks::now calls when EventClassLoad is not enabled

[Claes Redestad]

Thanks Ioi and David for reviewing,

sadly there was some issues with building the previous patch without the 
closed
sources which has been corrected here:

http://cr.openjdk.java.net/~redestad/8179040/hotspot.03/

Thanks!

/Claes

On 2017-08-23 20:11, Ioi Lam wrote:
> Hi Claes,
>
> The changes look good. Reviewed.
>
> Thanks
>
> - Ioi
>
>
> On 8/23/17 5:32 AM, Claes Redestad wrote:
>> Hi,
>>
>> this patch was never pushed due to an unfortunate interaction around 
>> cancelling
>> of events. Markus Grönlund has helped resolve these, while 
>> maintaining the
>> speedup:
>>
>> http://cr.openjdk.java.net/~redestad/8179040/hotspot.02/
>>
>> Thanks!
>>
>> /Claes
>>
>> On 04/25/2017 03:21 PM, Claes Redestad wrote:
>>> Hi,
>>>
>>> this patch removes calling Ticks::now when EventClassLoad isn't 
>>> enabled, which
>>> has an effect on class loading performance:
>>>
>>> http://cr.openjdk.java.net/~redestad/8179040/hotspot.01/
>>>
>>> When tracing isn't enabled trace/tracing.hpp has dummy 
>>> implementations which
>>> are easily optimized away by a compiler, which I've verified happens 
>>> on linux
>>> OpenJDK builds with tracing disabled.
>>>
>>> On builds with tracing enabled then the changes means the call to 
>>> get the time
>>> only happen if the event is enabled, which achieves the sought after 
>>> startup
>>> optimization.
>>>
>>> Thanks!
>>>
>>> /Claes
>>
>