Messages in this thread | | | Date | Mon, 20 Aug 2007 23:25:13 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [linux-usb-devel] [4/4] 2.6.23-rc3: known regressions |
| |
On Mon, 20 Aug 2007, Arjan van de Ven wrote: > > > > So it might be much better if we instead re-introduced that kind of "DMA > > latency requirement", and letting different subsystems react to that as > > they may. > > wait.... we HAVE that infrastructure .. see kernel/latency.c ...
Heh. Just shows how wellknown that interface is - it seems like it's only used by the ipw2100 driver and "pcm_native".
But yes, that looks like the right thing.
> and the C-state code will honor it. CPUFREQ doesn't honor it yet but > that's easy to add.. (this assumes the ACPI BIOS informs us correctly > about the cpu behavior, but that's the best we can do obviously unless > you want a table inside the kernel keyed off vendor/model/stepping)
Do we actually have the latency information for these things? Especially since I assume a number of people use the specialized direct-hw-access cpufreq drivers..
I realize that we *have* "transition_latency" at the cpufreq layer, and it is supposed to be in ns, but I wonder how likely it is to bear any relationship to reality, considering that I don't think it's really used for anything.. (yeah, it affects the heuristics, but I don't think it has any _hard_ meaning, so I'd worry that it's not necessarily something that people have tried to make accurate).
But I dunno.
Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |