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Message-Id: <1236934167.5188.195.camel@laptop> Date: Fri, 13 Mar 2009 09:49:27 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Jan Engelhardt <jengelh@...ozas.de> Cc: Arjan van de Ven <arjan@...radead.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: System tick rate On Thu, 2009-03-12 at 15:45 +0100, Jan Engelhardt wrote: > On Thursday 2009-03-12 15:21, Arjan van de Ven wrote: > >On Thu, 12 Mar 2009 14:38:19 +0100 (CET) Jan Engelhardt wrote: > >> > >> is there an "official" way of obtaining the current tick rate when > >> CONFIG_NO_HZ? > > > >what does "current tick rate" mean for you in a no-hz situation ? > >is it the HZ value (which is supposed to be invisible from userspace, > >so good luck) or the wakeup count ? > > Hm, I guess what I want is the number of timer interrupts which > occurred within the observation period that called the scheduler > code. (So that excludes RTC on usual x86en.) There is no tick rate with NO_HZ mode, only a max tick rate, but as Arjan said, not even that is exposed to user-space. I think Dave's Niagra has the crown here, because he ran into some bug in the NO_HZ code some while back because he idled longer than we ever seen before. I think it was in the order of 30 minutes or something without a single wakeup of the CPU. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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