On 06/18/2012 06:24 PM, Daniel Lezcano wrote:
> On 06/18/2012 02:25 PM, Deepthi Dharwar wrote:
>> Hi Daniel,
>>
>> On 06/18/2012 01:48 AM, Daniel Lezcano wrote:
>>
>>> On 06/15/2012 05:28 PM, Daniel Lezcano wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I have a dual core Intel T9500.
>>>>
>>>> I boot the cpu with the acpi_idle driver and intel_idle enabled in the
>>>> config.
>>>>
>>>> The kernel is booted with maxcpus=1.
>>>>
>>>> After the system has boot, I put cpu1 online via sysfs.
>>>>
>>>> But I don't see any 'cpuidle' directory in the cpu's sysfs entry:
>>>>
>>>> /sys/devices/system/cpu/cpu1/cpuidle (?)
>>>>
>>>> When I look at the code I see the notifier is present for hotplug in
>>>> processor_driver.c and the cpuidle intel init routine should be called
>>>> there.
>>>>
>>
>>
>> Yes, we have a hotplug notifier.
>> Commit 99b72508 by Thomas Renninger fixed this issue.
>>
>> Please let me know which kernel version you are running and what is idle
>> driver registered ?
>
> The kernel version is 3.5.0-rc1
> The registered driver is acpi_idle (with intel_idle if I am not wrong).
>
> Thomas's patch is in this version.
>
> Maybe I am wrong but I think the patch is not correct because:
>
> static int __cpuinit acpi_processor_add(struct acpi_device *device)
> {
>
> ...
>
> #ifdef CONFIG_SMP
> if (pr->id >= setup_max_cpus && pr->id != 0)
> return 0;
> #endif
>
> ...
>
> per_cpu(processors, pr->id) = pr;
>
> ...
> }
>
> With max_cpus=1 we exit before setting up 'pr'.
>
> So the condition in:
>
> static int acpi_cpu_soft_notify(...)
> {
>
> unsigned int cpu = (unsigned long)hcpu;
> struct acpi_processor *pr = per_cpu(processors, cpu);
>
> if (action == CPU_ONLINE && pr) {
>
> ...
> }
>
> Is always false because pr == NULL
>
> I did the change but I don't still see the 'cpuidle' directory
> appearing, I suspect also pr->flags.need_hotplug_init is not correctly
> initialized but I did not investigate more.
>
Well looks like variable maxcpus holds the key here.
When I am booting the system, say with 2 out of 4 available cpus,
set via maxcpus variable with intel_idle or acpi_idle and onlining the
other 2 cpus later via sysfs, I dont see cpufreq or cpuidle dir in the
sysfs path.
# cd /sys/devices/system/cpu/cpu2
xxx:/sys/devices/system/cpu/cpu2# ls
crash_notes node0 online
xxx:/sys/devices/system/cpu/cpu2# echo 1 > online
xxx:/sys/devices/system/cpu/cpu2# ls
cache crash_notes node0 online thermal_throttle topology
So looks like its designed that way for now.
So if maxcpus=X, X<Y where Y is no of available cpus.
Enabling the Y-X cpus later after the boot via sysfs is not enabling
cpuidle and cpufreq .
The question is, do we want to modify this behavior ?
Cheers,
Deepthi
