RE: [PATCH] raise tsc clocksource rating

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



> > Sigh, I don't really want to have this fight again.
> 
> i dont remember us having discussed this before, ever. If there's any
> "fight" about monotonicity and SMP then it would be a pretty onesided
> affair, with you being beaten up seriously ;-)

Actually, it is possible, even for NUMA systems with CPUs running off
completely different oscillators, and in the presence of CPU frequency
changes, power management, and even in the presence of thermal
throttling (though the latter introduces temporary inaccuracies it
doesn't affect monotonicity or rate).

Take a look at the Xen code to see how each physical CPU is
independently calibrated on an ongoing basis, how movement of VCPUs
between physical CPUs is tracked, and how shared variables are used to
ensure montonicity if a guest requires it. 

The fixed-rate TSCs on newer CPUs make some of this stuff easier, but
you still need to cope with different source oscillators and some power
management states.
 
Ian

> > I don't really see what point there is in raising the tsc's rating
> > (why is 300 insufficient again?), but regardless of the value, the
Xen
> > clocksource rating needs to be higher.
> 
> anyway, i agree that this patch cannot go in in its current form.
> 
> 	Ingo
> -
> To unsubscribe from this list: send the line "unsubscribe
linux-kernel"
> in
> the body of a message to [email protected]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux