Effect of Shenandoah Barriers on Code Size...

[Aleksey Shipilev]

On 09/09/2016 07:49 PM, Christine Flood wrote:
> One of the questions I got asked at VMM was "What is the effect of
> Shenandoah Barriers on Code Size?"
> 
> It would be nice to have some kind of measurement which we can talk
> about.

I guess we can do two things:
 a) say about the code size for standalone barriers, in comparison with
other collectors -- my recent disassemblies seem to answer that question
for C2/x86_64 [1][2], we may do the same for other platforms;
 b) estimate total increase in code heap size for, say, SPECjvm2008 and
Dacapo;

> My intuition is that it's negligible, but those dang write barriers.

To be blunt, current Shenandoah's write barriers are not worse than
current G1 write barriers, at least in the cases I cared about.

Thanks,
-Aleksey

[1]
http://cr.openjdk.java.net/~shade/shenandoah/shenandoah-gc-bench/src/main/java/org/openjdk/shenandoah/reads/ReadBarriersFields.java
[2]
http://cr.openjdk.java.net/~shade/shenandoah/shenandoah-gc-bench/src/main/java/org/openjdk/shenandoah/writes/WriteBarriers.java