In article <bc2d970909071917n12256d9ucee24327aec3d527_at_mail.gmail.com>, Ryan Stone <rysto32_at_gmail.com> wrote: >I'm not entirely clear on why it's done this way, but the timer is run at >twice hz for statistics-gathering purposes*. CPU usage statistics gathering >is driven off of the timer interrupt. Running the timer at twice hz may be >an attempt to eliminate clock-aliasing problems; if so, it's a poor way of >doing so. The statistics timer is supposed to be jittered with an exponential distribution, so that applications cannot avoid being charged for CPU time by running synchronously (and out-of-phase) with the timer. This was historically broken on PC hardware, and is probably still broken on SMP PC hardware, because there are insufficient programmable timer interrupts. Ideally, you'd like a distinct statistics timers on each CPU, with a sufficiently (quickly) programmable period. -GAWollmanReceived on Tue Sep 08 2009 - 03:43:16 UTC
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