Bpf next rdtsc #7977
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Bpf next rdtsc #7977
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New kfunc to return ARCH-specific timecounter. For x86 BPF JIT converts it into rdtsc ordered call. Other architectures will get JIT implementation too if supported. The fallback is to __arch_get_hw_counter(). Signed-off-by: Vadim Fedorenko <[email protected]> v2 -> v3: * change name of the helper to bpf_get_cpu_cycles_counter to explicitly mention what counter it provides (Andrii) * move kfunc definition to bpf.h to use it in JIT. * introduce another kfunc to convert cycles into nanoseconds as more meaningful time units for generic tracing use case (Andrii) v1 -> v2: * Fix incorrect function return value type to u64 * Introduce bpf_jit_inlines_kfunc_call() and use it in mark_fastcall_pattern_for_call() to avoid clobbering in case of running programs with no JIT (Eduard) * Avoid rewriting instruction and check function pointer directly in JIT (Alexei) * Change includes to fix compile issues on non x86 architectures
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The new helper should be used to convert cycles received by bpf_get_cpu_cycle_counter() into nanoseconds. Signed-off-by: Vadim Fedorenko <[email protected]>
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get_cpu_cycles_counter() is replaced with rdtsc instruction on x86_64. Add tests to check it. Signed-off-by: Vadim Fedorenko <[email protected]>
The selftest provides an example of how to measure the latency of bpf kfunc/helper call in cycles and nanoseconds. Signed-off-by: Vadim Fedorenko <[email protected]>
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