Date: Thu, 21 Nov 2013 12:19:23 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Bret Ketchum <bcketchum@gmail.com>, Alexander Motin <mav@freebsd.org> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: 9.1 callout behavior Message-ID: <CAJ-Vmokrchy4pXLvZ21sCV09fQUdYKeUYCEH1U1NdfDBxhyJQg@mail.gmail.com> In-Reply-To: <CAGm6yaTEFECTYVb94A13TaXMPSLtKLpTbw4iNdgd8SuNF1QDaA@mail.gmail.com> References: <CAGm6yaTEFECTYVb94A13TaXMPSLtKLpTbw4iNdgd8SuNF1QDaA@mail.gmail.com>
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Hi, It sounds like you may have found an interesting test case. Mav, any ideas? -adrian On 21 November 2013 05:20, Bret Ketchum <bcketchum@gmail.com> wrote: > I've a callout which runs every 100ms and does a bit of accounting > using the global ticks variable. This one-shot callout was called fairly > consistently in 8.1, every 100ms give or take a few thousand clocks. I've > recently upgraded to 9.1 and for the most part the period is consistent. > However, periodically the callout function is executed anywhere between 5ms > to 20ms after the callout was reset and the function returned while global > ticks has increased 8x. The hardware has not changed (using the same > timecounter configuration): > > CPU: Intel(R) Xeon(R) CPU E5-2640 0 @ 2.50GHz (2500.05-MHz K8-class CPU) > > kern.timecounter.hardware: TSC-low > kern.timecounter.tick: 1 > kern.timecounter.invariant_tsc: 1 > kern.timecounter.smp_tsc: 1 > > And default eventtimer configuration: > > kern.eventtimer.singlemul: 2 > kern.eventtimer.idletick: 0 > kern.eventtimer.activetick: 1 > kern.eventtimer.timer: LAPIC > kern.eventtimer.periodic: 0 > > If tickless mode is disabled the inconsistency goes away. Is the > premature expiration of the callout expected? Is the jump in global ticks > typical (say from 100 ticks to 800 ticks in 1.5ms)? > > Bret > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
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