Hi, I am doing some clean up in x86 ftrace code. I check the performance by switching between different tracers and by enabling and disabling them.
The operation has started to be much slower after rebasing on the kernel tip tree. Bisecting has shown that the difference was caused by the commit c229828ca6bc62d6c654 (rcu: Throttle rcu_try_advance_all_cbs() execution) The following times are from Intel 2xCore i7-3770 CPU @ 3.40GHz when calling the attached test script (time ./test-ftrace). It 100x switches between "function" and "nop" tracer. It also enables and disables the tracer each time. Results with the commit c229828ca6bc62d6c654: real 0m49.393s 0m49.632s 0m49.359s user 0m0.004s 0m0.000s 0m0.004s sys 0m0.996s 0m0.880s 0m0.892s Results after reverting the commit c229828ca6bc62d6c654: real 0m35.320s 0m35.687s 0m35.920s user 0m0.004s 0m0.004s 0m0.000s sys 0m1.140s 0m1.208s 0m1.152s I might do some more debugging on Monday. I wonder if you have any hints or ideas. Best Regards, Petr
test-ftrace
Description: application/shellscript
