Yep, we came up to the same conclusions in UST.
if we change all assignments to, e.g.:
then we can redefine the macros for filtering much more easily than with the
" = " assignment operator.
About your comment above, what is the problem with evaluating
"__trace_sched_switch_state(prev)" twice ? It will typically be cache-hot after
the first evaluation, so I wonder if, in practice, we really save a significant
amount of cycles by saving its result between filtering and writing into trace
buffers. As I pointed out earlier, for my customers, having a very, very fast
filter "out" case is more important that trying to squeeze a few cycles out of
the filter passed case.
Also, how many of these "__trace_sched_switch_state(prev)" are static inlines vs
actual function calls ? If it's mostly static inlines to dereference a few
pointers, doing it the second time when the filter passed won't hurt much.
Operating System Efficiency R&D Consultant