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https://issues.apache.org/jira/browse/GROOVY-12191?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Sun updated GROOVY-12191:
--------------------------------
Description:
h3. Problem
With invokedynamic enabled (default since Groovy 4), linked MOP call sites were
guarded by a *single process-wide* {{SwitchPoint}}
({{{}IndyInterface.switchPoint{}}}).
Any MetaClass registry change or category enter/leave invalidated that switch
point, so *every* linked site fell back and re-linked — including sites whose
receiver type was unrelated.
That global invalidation is expensive when MetaClass churn is common (e.g.
ExpandoMetaClass / mixins on startup or per-request paths, Grails-like
patterns). Unrelated hot monomorphic sites pay re-link and JIT deopt cost they
should not.
h3. Goal
Keep linked call sites optimized unless the *relevant* MetaClass state for that
site actually changed.
h3. Approach
One SwitchPoint domain {*}per class{*}, stored on {{{}ClassInfo{}}}:
* MetaClass change for type {{T}} retires {{{}T{}}}'s SwitchPoint *and* those
of loaded subtypes / implementors (hierarchy fan-out).
* Unrelated types keep their SwitchPoints; their call sites stay optimized.
* Category enter/leave (and {{{}VMPlugin.invalidateCallSites(){}}})
bulk-retire *all* loaded class SwitchPoints so sites re-link under the new
category state. There is *no* second category SwitchPoint on the hot path.
* Linked handles always install a *single* class-domain guard via
{{IndyInvalidation.guardWithMopSwitchPoints(...)}} — same monomorphic guard
shape as before, without global deopt on unrelated MetaClass churn.
Final classes short-circuit hierarchy fan-out (no full {{ClassInfo}} scan).
Non-final types batch retirements with {{{}SwitchPoint.invalidateAll{}}}.
h3. Invalidation map
||Event||What is retired||
|MetaClass change for type {{T}} (registry /
{{{}ClassInfo.incVersion{}}})|{{T}} + loaded subtypes / implementors|
|Category enter/leave, {{invalidateCallSites()}}|All loaded class SwitchPoints
(bulk)|
|Unattributed MetaClass registry event|All loaded class SwitchPoints (bulk)|
|First MetaClass *install* on a class|Version bump only (no linked sites yet);
replacement / clear retires that class's SwitchPoint|
was:
h3. Problem
With invokedynamic enabled (default since Groovy 4), linked MOP call sites were
guarded by a *single process-wide* {{SwitchPoint}}
({{IndyInterface.switchPoint}}).
Any MetaClass registry change or category enter/leave invalidated that switch
point, so *every* linked site fell back and re-linked — including sites whose
receiver type was unrelated.
That global invalidation is expensive when MetaClass churn is common (e.g.
ExpandoMetaClass / mixins on startup or per-request paths, Grails-like
patterns). Unrelated hot monomorphic sites pay re-link and JIT deopt cost they
should not.
h3. Goal
Keep linked call sites optimized unless the *relevant* MetaClass state for that
site actually changed.
h3. Approach (minimal model)
One SwitchPoint domain *per class*, stored on {{ClassInfo}}:
* MetaClass change for type {{T}} retires {{T}}'s SwitchPoint *and* those of
loaded subtypes / implementors (hierarchy fan-out).
* Unrelated types keep their SwitchPoints; their call sites stay optimized.
* Category enter/leave (and {{VMPlugin.invalidateCallSites()}}) bulk-retire
*all* loaded class SwitchPoints so sites re-link under the new category state.
There is *no* second category SwitchPoint on the hot path.
* Linked handles always install a *single* class-domain guard via
{{IndyInvalidation.guardWithMopSwitchPoints(...)}} — same monomorphic guard
shape as before, without global deopt on unrelated MetaClass churn.
Final classes short-circuit hierarchy fan-out (no full {{ClassInfo}} scan).
Non-final types batch retirements with {{SwitchPoint.invalidateAll}}.
h3. Invalidation map
||Event||What is retired||
|MetaClass change for type {{T}} (registry / {{ClassInfo.incVersion}})|{{T}} +
loaded subtypes / implementors|
|Category enter/leave, {{invalidateCallSites()}}|All loaded class SwitchPoints
(bulk)|
|Unattributed MetaClass registry event|All loaded class SwitchPoints (bulk)|
|First MetaClass *install* on a class|Version bump only (no linked sites yet);
replacement / clear retires that class's SwitchPoint|
h3. Binary compatibility
{{IndyInterface.switchPoint}} is retained and rotated on category /
{{invalidateCallSites}} for external observers, but is *no longer* the MOP
guard on linked call sites (documented as deprecated for that use). New code
uses {{IndyInvalidation}}.
> Scope indy SwitchPoint invalidation
> -----------------------------------
>
> Key: GROOVY-12191
> URL: https://issues.apache.org/jira/browse/GROOVY-12191
> Project: Groovy
> Issue Type: Improvement
> Reporter: Daniel Sun
> Priority: Major
>
> h3. Problem
> With invokedynamic enabled (default since Groovy 4), linked MOP call sites
> were guarded by a *single process-wide* {{SwitchPoint}}
> ({{{}IndyInterface.switchPoint{}}}).
> Any MetaClass registry change or category enter/leave invalidated that switch
> point, so *every* linked site fell back and re-linked — including sites whose
> receiver type was unrelated.
> That global invalidation is expensive when MetaClass churn is common (e.g.
> ExpandoMetaClass / mixins on startup or per-request paths, Grails-like
> patterns). Unrelated hot monomorphic sites pay re-link and JIT deopt cost
> they should not.
> h3. Goal
> Keep linked call sites optimized unless the *relevant* MetaClass state for
> that site actually changed.
> h3. Approach
> One SwitchPoint domain {*}per class{*}, stored on {{{}ClassInfo{}}}:
> * MetaClass change for type {{T}} retires {{{}T{}}}'s SwitchPoint *and*
> those of loaded subtypes / implementors (hierarchy fan-out).
> * Unrelated types keep their SwitchPoints; their call sites stay optimized.
> * Category enter/leave (and {{{}VMPlugin.invalidateCallSites(){}}})
> bulk-retire *all* loaded class SwitchPoints so sites re-link under the new
> category state. There is *no* second category SwitchPoint on the hot path.
> * Linked handles always install a *single* class-domain guard via
> {{IndyInvalidation.guardWithMopSwitchPoints(...)}} — same monomorphic guard
> shape as before, without global deopt on unrelated MetaClass churn.
> Final classes short-circuit hierarchy fan-out (no full {{ClassInfo}} scan).
> Non-final types batch retirements with {{{}SwitchPoint.invalidateAll{}}}.
> h3. Invalidation map
> ||Event||What is retired||
> |MetaClass change for type {{T}} (registry /
> {{{}ClassInfo.incVersion{}}})|{{T}} + loaded subtypes / implementors|
> |Category enter/leave, {{invalidateCallSites()}}|All loaded class
> SwitchPoints (bulk)|
> |Unattributed MetaClass registry event|All loaded class SwitchPoints (bulk)|
> |First MetaClass *install* on a class|Version bump only (no linked sites
> yet); replacement / clear retires that class's SwitchPoint|
>
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