Date: Tue, 27 Oct 2015 15:50:01 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-hackers <freebsd-hackers@FreeBSD.org>, Poul-Henning Kamp <phk@phk.freebsd.dk>, Jung-uk Kim <jkim@FreeBSD.org> Subject: Re: instability of timekeeping Message-ID: <562F8109.4050203@FreeBSD.org> In-Reply-To: <20151027115810.GU2257@kib.kiev.ua> References: <56261398.60102@FreeBSD.org> <56261FE6.90302@FreeBSD.org> <56274FFC.2000608@FreeBSD.org> <20151021184850.GX2257@kib.kiev.ua> <562F3E2F.2010100@FreeBSD.org> <20151027115810.GU2257@kib.kiev.ua>
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On 27/10/2015 13:58, Konstantin Belousov wrote: > On Tue, Oct 27, 2015 at 11:04:47AM +0200, Andriy Gapon wrote: >> And now another observation. I have C1E option enabled in BIOS. It >> means that if all cores enter C1 state, then the whole processor >> is magically placed into a deep C-state (C3, I think). LAPIC timer >> on this CPU model does not run in the deep C-state. So, I had to >> disable C1E option to test the LAPIC timer in a useful way. But >> before actually testing it I first tried to reproduce the problem. As >> you might have already guessed the problem is gone with that option >> disabled. Scratching my head to understand the implications of this >> observation. > > Most obvious explanation would be that the latency of wakeup is very large. > What is the HPET frequency when the jitter occur ? > kern.timecounter.tc.TSC-low.frequency: 1607351869 kern.eventtimer.et.HPET.frequency: 14318180 Or did you mean the actual rate of timer interrupts? -- Andriy Gapon
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