>On Fri, 30 Nov 2007 14:06:55 -0800 >"Pallipadi, Venkatesh" <venkatesh.pallipadi@xxxxxxxxx> wrote: > >Please dont go off-list like this. I put Mark's original >mailing list cc's >back. Sorry for missing some cc's earlier. I blindly did a reply-all to the mm-commits mail I got. >> I will have to Nack this. The reason max_cstate was initentionally >> removed due to couple of reasons: > >It broke userspace without any warning or migration period, afaict. Yes. That's true. I will have to take the blame for that. It has been known for a while during cpuidle development. But, it was never documented as deprecating. >> 1) All in kernel users of max_cstate should rather be using >> pm_qos/latency interfaces. All such max_cstate usages must already be >> migrated. > >That code isn't merged. All kernel part is already merged. I mean, there are do drivers that depend on max_cstate. They use latency_notifier thing today and their migration to pm_qos part is not merged yet. >> 2) Supporting max_cstate as a dynamic parameter cleanly is no longer >> possible in acpi/processor_idle.c as the C-state policy has moved to >> cpuidle instead. It can be done if it is needed. But, just >below patch >> will not really work with cpuidle. >> >> Selecting max_cstate at boot time as a debug option still >works without >> this patch. >> >> So, just this patch will not get back the functionality with cpuidle. >> Infact changing it at run time will have no effect. Question >however is: >> Is there a real need to revive this parameter so that user can change >> max_cstate at run time? > >It is not known whether Mark is actually writing to this >thing. Perhaps >read-only permissions would be a suitable fix? > Exporting it as read only should be OK. We also need to know if there are hard user space dependency on writing to this from userspace. Thanks, Venki - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
