Hi - On Tue, Apr 28, 2009 at 11:10:10AM -0700, Roland McGrath wrote: > [...] > The microbenchmark makes that seem like more of a sensical comparison than > it really is. They are really apples and oranges. The TIF_SYSCALL_TRACE > types (process.syscall) add some overhead to every system call. The probe > types (kprobe/tracepoint/marker) add overhead only to the probed call.
Certainly, in general. But in this specific test, only the under-test system calls occurred in essnetially the whole system, so the overhead measurements were in a way the bare minimums imposed by the kprobes vs. utrace callback infrastructure itself. > In real situations [...] the distribution of overheads will be > quite different. Or rather, the basic overhead quanta measured above may be multiplied along several different axes. - FChE