Zero-Overhead USDT Probes Without sys/sdt.h
The previous two posts built a GCC plugin that writes a trace file on every function entry and exit. That works well for offline analysis but has a cost: every call executes a spinlock check, a gettid syscall, a hex formatting loop, and a writev. Even with the lock already open and O_APPEND in place, that is work happening on every function call in your program.
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