On August 18, 2016 5:51:31 PM GMT+02:00, Andi Kleen <a...@firstfloor.org> wrote: >> I'd prefer to make updates atomic in multi-threaded applications. >> The best proxy we have for that is -pthread. >> >> Is it slower, most definitely, but odds are we're giving folks >> garbage data otherwise, which in many ways is even worse. > >It will likely be catastrophically slower in some cases. > >Catastrophically as in too slow to be usable. > >An atomic instruction is a lot more expensive than a single increment. >Also >they sometimes are really slow depending on the state of the machine.
The important part is to optimize increments in loops - sth we have special ways to do for the regular counters. OTOH if we can delay instrumenting to late enough we can instrument loops optimized in the first place. Richard. >-Andi
