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Here's a simple patch to put a upper-bound on how much system time is consumed by SystemTap. It keeps a cumulative sum of time spent in probes on each cpu, and if that exceeds the threshold within an interval, the session is aborted. Advantages: * Accounting is maintained per-cpu. * The frequency of get_cycles() is irrelevant to calculations, even if it changes. * The code is very simple. :) Disadvantages: * Doesn't account for overhead in firing the probe (e.g., the cost of a debug trap). * Doesn't detect excessive overhead from multiple scripts (e.g., ten scripts that individually run under the threshold could together bear down the system). TODO: * Share some code with STP_TIMING (which also tracks probe duration). * Make the threshold tunable (by gurus only?). * Account for other runtime overhead (transport, timer sync, etc.). * Make exceptions for some probes (begin, end) Comments and suggestions are welcome... Josh
Attachment:
stp_accounting.patch
Description: stp_accounting.patch
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