Messages in this thread |  | | Date | Fri, 16 Feb 2007 23:36:57 -0500 | From | Jeff Muizelaar <> | Subject | Re: Using sched_clock for mmio-trace |
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On Fri, Feb 16, 2007 at 02:47:45PM -0800, Daniel Walker wrote: > > > Gets pretty ugly .. The clocksource interface already has a positive > > > rating to describe the "best" clocks in the system, which is used to > > > return the "best" clock .. Where the maintainers of the system give each > > > clock a rating. I would imagine most people would just get the so called > > > "best" clock which has the best rating.. > > > > > > I'm starting to think this long flags stringing effect could happen with > > > negative flags also, but it's seems a lot less likely. > > > > The amount of flag stringing should be the same. > > I don't think so .. The common case with negative flags is no flags, > then next would be CLOCKSOURCE_UNSTABLE. At most I would guess two > flags .. The other direction your likely to have people using all flags > most of the time. That's why I showed a function call with all the flags > listed.
I think you still misunderstand me. The common case is still no flags.
clocksource_get_clock_must_have(0) would return clocks that are stable and unstable. clocksource_get_clock_must_have(CLOCKSOURCE_STABLE) would only return clocks that are stable, just like clocksource_get_clock_masked(CLOCKSOURCE_UNSTABLE) only returns clocks that are stable.
> > > > instead of > > > > > > > > clocksource_get_clock_masked(CLOCKSOURCE_UNSTABLE) > > > > clocksource_get_clock_masked(CLOCKSOURCE_PM_AFFECTED) > > > > > > > > Especially awkward is the CLOCKSOURCE_64BIT flag, as there isn't really > > > > anyway to specify that I want a 64bit timer, only a way to specify that > > > > I don't. > > > > > > I might add a way to get specific flags, but I still think the flags > > > should be mostly negative features. > > > > Yeah, the problem is that all of the features are negative except for > > CLOCKSOURCE_64BIT, so you can't mask for it. > > It's meant as a negative feature. So you can mask it if you can't handle > the math .. The only 64bit clock I know off is the tsc, and it's got the > highest rating of all clocks.
Ah ok, I see that now. Maybe CLOCKSOURCE_OVER_32BITS would be a better name? It might convey the negativity better...
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