On Mon, Jan 7, 2019 at 5:32 PM Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > 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. Focusing on counter performance is, IMHO, missing the mark. Even if interrupt count collection were made fast, there's *something* in any particular /proc file that a particular reader doesn't need and that, by being uselessly collected, needlessly slows that reader. There should be a general-purpose way for /proc file readers to tell the kernel which bits of information interest them on a particular read syscall sequence or particular open(2) or something. Creating a new proc file for every useful combination of attributes doesn't scale either.
