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

[Claes Redestad]

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