----- Original Message ----- > From: "Steven Rostedt" <rostedt@xxxxxxxxxxx> > To: "Mathieu Desnoyers" <mathieu.desnoyers@xxxxxxxxxxxx> > Cc: "tip-bot for Thomas Gleixner" <tipbot@xxxxxxxxx>, linux-tip-commits@xxxxxxxxxxxxxxx, "john stultz" > <john.stultz@xxxxxxxxxx>, hpa@xxxxxxxxx, mingo@xxxxxxxxxx, peterz@xxxxxxxxxxxxx, tglx@xxxxxxxxxxxxx > Sent: Wednesday, July 23, 2014 8:31:02 PM > Subject: Re: [tip:timers/core] ftrace: Provide trace clocks monotonic > > On Thu, 24 Jul 2014 00:20:11 +0000 (UTC) > Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > > > > Therefore, calling it with the same name as the specific user-visible clock > > it can correlate with (CLOCK_MONOTONIC) seems like a sane choice to me. > > Then perhaps we should call it "CLOCK_MONOTONIC". "mono" to me appears > that the clock is home sick in bed because it kissed someone it > shouldn't have. The main difference here is that time returned by CLOCK_MONOTONIC is expected to never go backwards between two consecutive reads of a single caller thread. This new clock does not provide this guarantee, even though it can be correlated with CLOCK_MONOTONIC. I see this clock as being fundamentally the same clock source as clock monotonic, to which we apply a spreading filter than can fuzz the returned value so the lower bits can go slightly forward or backwards. If we call this clock "CLOCK_NMI_SAFE", and document that it can be correlated with CLOCK_MONOTONIC, we might end up in a bad situation if we ever want to apply this same trick to export another nmi-safe clock, e.g. REALTIME or MONOTONIC_RAW. Therefore, it would be good to keep the name of the clock it correlated to in the name (monotonic). We're been going through a brainstorm here, here is what we have so far. CLOCK_MONOTONIC_x, where x is: - FUZZED, - SPREAD, - DISPERSED, - DIFFUSE, - UNORDERED, - WEAK, - NMI_SAFE, - MOSTLY, - ARGUABLY, - WHEN_MOON_IS_IN_CRESCENT, and then it went downhill from there. ;-) Thoughts ? Thanks, Mathieu > > -- Steve > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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