Daniel Sun created GROOVY-12191:
-----------------------------------
Summary: Scope indy SwitchPoint invalidation and harden PIC/math
paths
Key: GROOVY-12191
URL: https://issues.apache.org/jira/browse/GROOVY-12191
Project: Groovy
Issue Type: Improvement
Reporter: Daniel Sun
h3. Problem this targets
With invokedynamic enabled (default since Groovy 4), a *single process-wide*
{{SwitchPoint}} guarded essentially all linked MOP call sites. Any MetaClass
registry change or category enter/leave invalidated that switch point, so *all*
sites fell back and re-linked — including sites whose receiver type was
unrelated.
That global invalidation shows up as:
* Startup / request paths with ExpandoMetaClass / mixins (Grails-like
patterns) pay repeated re-link cost
* Category {{use}} thrashing deoptimizes the whole application
* JMH benches under {{subprojects/performance}} document this cost pattern
h3. What changes proposed
Four complementary layers under the indy / MOP runtime:
||#||Area||Behaviour||
|1|Scoped SwitchPoint invalidation|Per-{{{}ClassInfo{}}} domain + hierarchy
fan-out to loaded subtypes; separate *category-global* domain for
{{{}use(Category){}}}. MetaClass change for class {{A}} no longer invalidates
sites for unrelated class {{B}}|
|2|PIC polymorphism policy|{{CallSiteTracker}} counts distinct receiver shapes;
at {{max.poly}} the site becomes sticky *megamorphic* (pin default boot target,
no monomorphic {{setTarget}} thrash). Selection stays amortized via the PIC|
|3|Bimorphic promote|Two stable receiver shapes can share one nested
{{guardWithTest}} target instead of alternating monomorphic targets|
|4|IndyMath completeness|BigDecimal-category ops (and mixed integral+BD) via
{{{}NumberMath{}}}; {{div}} / {{{}intdiv{}}}; primitive {{rightShiftUnsigned}}
table entries. Shift ops stay off the GeneratedMetaMethod→IndyMath fast path so
mixed {{{}int{}}}/{{{}long{}}} keeps left-operand result typing|
h3. Invalidation model (after the changes)
||Domain||Invalidated when||Guards||
|Per-class (+ subtypes)|{{ClassInfo.incVersion}} / MetaClass registry change
for that type|Receiver class (or {{Class}} for static sites); hierarchy fan-out
invalidates subtype SwitchPoints|
|Category-global|Category enter/leave
({{{}VMPlugin.invalidateCallSites{}}})|Always dual-guarded with the class
domain; *never* fails over (correctness)|
Per-class SwitchPoint can fail over after repeated retirements (default 100) to
a {{ClassInfo.version}} equality guard (avoids permanent-invalid SP recursion).
Concurrent failover drains any raced-in SwitchPoint so none remains valid after
the domain has failed over. Category domain stays unlimited.
Generation bump on MetaClass *replacement* / clear retires that class's
SwitchPoint; first MetaClass install only bumps version (no linked sites yet).
Hierarchy fan-out remains on {{incVersion}} and registry listeners.
h3. Tunables (system properties)
||Property||Default||Meaning||
|{{groovy.indy.switchpoint.max.failures}}|{{100}}|Live SP retirements before
per-class failover (value less than or equal to 0 = unlimited)|
|{{groovy.indy.invalidation.stats}}|{{false}}|Log invalidation counters|
|{{groovy.indy.callsite.max.poly}}|{{8}}|Distinct shapes to sticky megamorphic
(value less than or equal to 0 disables)|
|{{groovy.indy.callsite.mega.sticky}}|{{true}}|Mega flag survives shape clear|
|{{groovy.indy.callsite.bimorphic}}|{{true}}|Allow dual-shape target promote|
|{{groovy.indy.callsite.cache.size}}|{{8}}|PIC LRU size|
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