Messages in this thread | | | Date | Sat, 05 Jan 2008 11:27:21 -0500 | From | Mark Lord <> | Subject | Re: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree |
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Pallipadi, Venkatesh wrote: >> -----Original Message----- >> From: Mark Lord [mailto:lkml@rtr.ca] .. >> Okay, with !CONFIG_CPU_IDLE, this works fine -- same as 2.6.23 >> and earlier. >> > > Good to know. Atleast we do not have a regression for 2.6.24 now. ..
Agreed. We're happy here, for now.
>>> Meanwhile, can you give a short summary of how behaviour differs >>> between CONFIG_CPU_IDLE and !CONFIG_CPU_IDLE ?? >>> >>> I'm not at all clear on how this really affects things. > > With CPU_IDLE, the C-state policy is removed from acpi driver. Ideally > policy should have nothing to do with ACPI, as ACPI only provides the > C-state mechanisms. So, with CPU_IDLE, it is not easy to control this > variable through a acpi driver module at run time. Also, the latency > interface that was mentioned before is to serve the same purpose in a > more clear manner (based on the wakeup latency) instead of a C-state > number which may not mean much from the end user point of view. > > I will look at why latency does not work on a single core system > soon(Was that with UP kernel or SMP kernel?). That way we will have a > proper cover for this with CPU_IDLE in future. ..
That was with a UP kernel on a UP box.
The latency thingie really seemed to have little or no effect, whereas setting max_cstate=1 has a quite noticeable positive impact.
Things seemed okay (with the latency thingie) on the SMP machine, but with two cores it is probably simply more forgiving.
cheers
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