v.25.9Improvement

Add ability to tune pending signals

Official CH changelog text
Add ability to tune pending signals in attempt to overcome CANNOT_CREATE_TIMER (for query profilers, query_profiler_real_time_period_ns/query_profiler_cpu_time_period_ns). And also collect SigQ from the /proc/self/status for introspection (if ProcessSignalQueueSize is near to ProcessSignalQueueLimit, then you will likely get CANNOT_CREATE_TIMER errors). #86760 (Azat Khuzhin).
Added tuning options for pending signals to help prevent CANNOT_CREATE_TIMER errors in query profilers by adjusting query_profiler_real_time_period_ns and query_profiler_cpu_time_period_ns. Also introduced collection of SigQ from /proc/self/status to monitor signal queue usage for better introspection.

Why it matters

This feature addresses the issue where excessive signals cause CANNOT_CREATE_TIMER errors during query profiling. By tuning the pending signal parameters and monitoring the signal queue size via SigQ, users can diagnose and mitigate timer creation failures, improving reliability and stability of query profiling.

How to use it

Users can tune the signal period settings by configuring query_profiler_real_time_period_ns and query_profiler_cpu_time_period_ns to reduce pending signals. Additionally, SigQ metrics from /proc/self/status are collected automatically for introspection. Monitoring the ProcessSignalQueueSize against ProcessSignalQueueLimit helps determine if tuning is needed to avoid CANNOT_CREATE_TIMER errors.

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