RFR (XS): Set matrix update probability to low in conditional

Aleksey Shipilev shade at redhat.com
Mon Mar 20 13:26:57 UTC 2017


Hi,

We can make the generated code a bit better by putting "unlikely" branch profile
hint on the conditional matrix update:
 http://cr.openjdk.java.net/~shade/shenandoah/matrix-c2-prob/webrev.01/

Seems to help workloads that are sensitive to matrix barriers:

Benchmark            Mode  Cnt    Score   Error    Units

# Baseline, -UseMatrix
Compiler.compiler   thrpt   50   93.041 ± 1.177  ops/min
Compiler.sunflow    thrpt   50  225.488 ± 3.148  ops/min
XmlValidation.test  thrpt   50  284.879 ± 1.190  ops/min

# Baseline, +UseMatrix
Compiler.compiler   thrpt   50   79.702 ± 0.805  ops/min
Compiler.sunflow    thrpt   50  197.360 ± 2.629  ops/min
XmlValidation.test  thrpt   50  254.786 ± 0.881  ops/min

# Patched, +UseMatrix
Compiler.compiler   thrpt   50   82.011 ± 0.865  ops/min
Compiler.sunflow    thrpt   50  202.404 ± 3.808  ops/min
XmlValidation.test  thrpt   50  257.733 ± 0.912  ops/min

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey



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