Date: Sun, 21 Jan 2018 14:22:05 -0700 From: Ian Lepore <ian@freebsd.org> To: Hans Petter Selasky <hps@selasky.org>, Johannes Lundberg <johalun0@gmail.com> Cc: freebsd-current <freebsd-current@freebsd.org> Subject: Re: Periodical interrupt storm when playing game with USB keyboard Message-ID: <1516569725.42536.99.camel@freebsd.org> In-Reply-To: <64218617-98d2-0e6e-5872-e44106e61bf7@selasky.org> References: <CAECmPwvDQBYw=mKJpZfUdKpXSC8GysZKSk0f9qaZEXCvy_QeMA@mail.gmail.com> <e2851846-0678-5cb9-0fce-e9cf49c41a2e@selasky.org> <CAECmPwvgMDBTUjhAERe4bKLgNYCim9bwdHw2JEL0RgTckMjSDw@mail.gmail.com> <CAECmPwtWr0t5_xLgg4NMxnjz317sqnfR9-ttH62szq4fwPdO=Q@mail.gmail.com> <64218617-98d2-0e6e-5872-e44106e61bf7@selasky.org>
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On Sun, 2018-01-21 at 22:07 +0100, Hans Petter Selasky wrote: > On 01/21/18 21:45, Johannes Lundberg wrote: > > > > What does kern.eventtimer.periodic do? The sysctl description > > wasn't > > that elaborate... > It turns off re-programming the timer every time there is a new > callout > with earlier completion time. > > --HPS Well, it does more than that. It makes the system run "the old way" where there are periodic timer interrupts that happen whether they need to or not (bad for power saving), and there's no way to schedule anything to happen on intervals other than when the periodic ticks occur (so if kern.hz = 1000 and you ask to sleep for a microsecond you may actually sleep up to a millisecond). -- Ian
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