On Mon, Jan 07, 2019 at 10:12:56AM -0500, Waiman Long wrote: > As newer systems have more and more IRQs and CPUs available in their > system, the performance of reading /proc/stat frequently is getting > worse and worse. Because the "roll-your-own" per-cpu counter implementaiton has been optimised for low possible addition overhead on the premise that summing the counters is rare and isn't a performance issue. This patchset is a direct indication that this "summing is rare and can be slow" premise is now invalid. We have percpu counter infrastructure that trades off a small amount of addition overhead for zero-cost reading of the counter value. i.e. why not just convert this whole mess to percpu_counters and then just use percpu_counter_read_positive()? Then we just don't care how often userspace reads the /proc file because there is no summing involved at all... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
