EscapeAnalysis diagnostics + user-guided stack allocation

[Vladimir Kozlov]

Vitaly Davidovich wrote:
> Hi,
> 
> Is there a way, in product build, to get diagnostics on EA? For example, 
> to see which allocations in a method are removed? I realize EA is an 
> implementation detail and subject to change release to release, but it 
> would be a great option to have for performance tuning.  There are many 
> classes which are simple wrappers on top of a primitive (e.g. Apache's 
> HashCodeBuilder, EqualsBuilder) which people use, and if the allocations 
> are not removed, they create a lot of GC pressure.  In cases where EA 
> does not remove them, it would be advantageous to hand-code the 
> functionality instead of using these utility wrappers.  However, the 
> only way to know right now (to my knowledge) is to look at disassembly 
> via hsdis -- it'd be great if there was a simpler and quicker way to do 
> that check.

There is debug flag PrintEliminateAllocations. Nobody asked before to make it 
available but we can change it to diagnostic flag.

> 
> Also, are there any plans to support struct/value-type like (ala CLR's 
> struct) constructs in the JVM (presumably java can then target it)? This 
> would allow developer to control where something gets allocated without 
> relying on EA, and it would also reduce the amount of indirection in 
> object graphs (and the mem/cpu performance hit of them) since struct 
> members of a heap allocated object could be allocated "inline". 
>  Apologies if this mailgroup isn't the most appropriate for this 
> particular question, so feel free to redirect me to the right one.

I don't known about such plans. Send this question to hotspot-dev at openjdk.java.net

Vladimir

> 
> Thanks
> 
> -- 
> Vitaly
> 617-548-7007 (mobile)