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  "title": "High latency cause detection using multilevel dynamic analysis",
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  "authors": [
    "Naser Ezzati-Jivan",
    "Genevieve Bastien",
    "Michel R. Dagenais"
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    "venue": "IEEE Systems Conference",
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  "description": "The paper correlates PHP user-space events with LTTng kernel events in a unified multilevel model to explain high-latency web requests.",
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    "method": "Instrument PHP and correlate its call/compile events with LTTng-UST and kernel states in a common timestamped model. Mapping rules and an FSM reconstruct PHP call-stack state; synchronized views and a Critical Path View expose blocking and preemption.",
    "findings": "The simple example identifies compile/cache time, while the Drupal example identifies OPcache shared-memory lock contention that is invisible in PHP-only analysis. Minimal cross-layer tracing limits overhead to below 7.5% in the reported client sweep.",
    "limitations": "The implementation and evaluation are PHP-specific; the paper does not establish transferability to other runtimes or web stacks. Full tracing has substantial throughput cost, and the compile percentage is case-specific.",
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