Hi! > On Wed, Feb 15, 2017 at 11:24:26AM +0100, Pavel Machek wrote: > > On Sun 2017-02-12 00:41:54, Willy Tarreau wrote: > > > The "activity" trigger was inspired by the heartbeat one, but aims at > > > providing instant indication of the immediate CPU usage. Under idle > > > condition, it flashes 10ms every second. At 100% usage, it flashes > > > 90ms every 100ms. The blinking frequency increases from 1 to 10 Hz > > > until either the load is high enough to saturate one CPU core or 50% > > > load is reached on a single-core system. Then past this point only the > > > duty cycle increases from 10 to 90%. > > > > > > This results in a very visible activity reporting allowing one to > > > immediately tell whether a machine is under load or not, making it > > > quite suitable to be used in clusters. > > > > > > Signed-off-by: Willy Tarreau <w@xxxxxx> > > > > Hmm. Evil question. Why not use LEDS_TRIGGER_CPU instead? > > > > Recently it gained support for "summarizing" all the cpus onto one > > led. > > That's not an evil question, it's perfectly correct as it's the first > one I've tried :-) But it's basically an all on or all off report, you > see if the CPU is instantly being used or not. Also, when the CPU is > idle you have no way to tell the machine is not dead, and when it's > saturated you have no way to check it's not stuck. In the end I found > the lack of progressivity in the visual report to be very problematic > for my typical use case where I want to be able to spot in one second > if a machine in my build farm is under-loaded. Well, when I used this kind of LED, it usually did flicker even on "idle" systems, because system is never idle. But you are right, it is easy for 100% cpu to be used, and then you could not tell if it is stuck. > I thought about modifying the cpu trigger to support a different mode > of reporting but I noticed that the two approaches are quite different > and very likely suit different purposes, even if there can be some > overlap for a number of use cases. I think that most users just want > to see if something is running or draining their battery and CPU is > better suited there. But to differenciate between 10, 50 and 100% > usage, it really is not (at least for me). ...so this makes sense. Best regards, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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