search for: __cov_increment

On Fri, Apr 18, 2014 at 12:13 AM, Dmitry Vyukov <dvyukov at google.com> wrote: > Hi, > > This is long thread, so I will combine several comments into single email. > > > >> - 8-bit per-thread counters, dumping into central counters on overflow. > >The overflow will happen very quickly with 8bit counter. > > Yes, but it reduces contention by 256x (a thread

...). > But statistically it should be no more than 2x away from the real counter. > Will this accuracy be enough for the major use cases? > > Moreover, this approach allows to implement the counter increment using a callback: > if ((fast_thread_local_rand() & counter) == 0) __cov_increment(&counter); > which in turn will let us use the same hack as in AsanCoverage: use the PC to map the counter to the source code. > (= no need to create separate section in the objects). > > Thoughts? > > —kcc I can see that the behavior of our current instrumentation is goi...