On Wed, 2013-08-07 at 07:06 +0200, Ondřej Bílka wrote: > Add short_counter,long_counter and before increment counter before each > jump. That way we will know how many short/long jumps were taken.
That's not trivial at all. The jump is a single location (in an asm goto() statement) that happens to be inlined through out the kernel. The assembler decides if it will be a short or long jump. How do you add a counter to count the difference? The output I gave is from the boot up code that converts the jmp back to a nop (or in this case, the default nop to the ideal nop). It knows the size by reading the op code. This is a static analysis, not a running one. It's no trivial task to have a counter for each jump. There is a way though. If we enable all the jumps (all tracepoints, and other users of jumplabel), record the trace and then compare the trace to the output that shows which ones were short jumps, and all others are long jumps. I'll post the patches soon and you can have fun doing the compare :-) Actually, I'm working on the 4 patches of the series that is more about clean ups and safety checks than the jmp conversion. That is not controversial, and I'll be posting them for 3.12 soon. After that, I'll post the updated patches that have the conversion as well as the counter, for RFC and for others to play with. -- Steve
