Re: [PATCH V3 0/4] genirq/affinity: irq vector spread among online CPUs as far as possible

[Dou Liyang]

Hi Artem,

At 03/14/2018 11:29 AM, Dou Liyang wrote:
> Hi All,
>
> At 03/13/2018 05:35 PM, Rafael J. Wysocki wrote:
> > On Tue, Mar 13, 2018 at 9:39 AM, Artem Bityutskiy 
> > <dedekind1@xxxxxxxxx> wrote:
> > > On Tue, 2018-03-13 at 16:35 +0800, Ming Lei wrote:
> > > > Then looks this issue need to fix by making possible CPU count
> > > > accurate
> > > > because there are other resources allocated according to
> > > > num_possible_cpus(),
> > > > such as percpu variables.
> > >
> > > Short term the regression should be fixed. It is already v4.16-rc6, we
> > > have little time left.
> >
> > Right.
> >
> > > Longer term, yeah, I agree. Kernel's notion of possible CPU count
> > > should be realistic.
>
> I did a patch for that, Artem, could you help me to test it.

I didn't consider the nr_cpu_ids before. please ignore the old patch and
try the following RFC patch.

Thanks
	dou

--------------------------->8-------------------------------------

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 449d86d39965..96d568408515 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -671,6 +671,23 @@ static acpi_status __init 
acpi_processor_ids_walk(acpi_handle handle,

 }

+static void __init acpi_refill_possible_map(void)
+{
+       unsigned int cpu, nr = 0;
+
+       if (nr_cpu_ids <= nr_unique_ids)
+               return;
+
+       for_each_possible_cpu(cpu) {
+               if (nr >= nr_unique_ids)
+                       set_cpu_possible(cpu, false);
+               nr++;
+       }
+
+       nr_cpu_ids = nr_unique_ids;
+       pr_info("Allowing %d possible CPUs\n", nr_cpu_ids);
+}
+
 static void __init acpi_processor_check_duplicates(void)
 {
        /* check the correctness for all processors in ACPI namespace */
@@ -680,6 +697,9 @@ static void __init acpi_processor_check_duplicates(void)
                                                NULL, NULL, NULL);
        acpi_get_devices(ACPI_PROCESSOR_DEVICE_HID, 
acpi_processor_ids_walk,
                                                NULL, NULL);
+
+       /* make possible CPU count more realistic */
+       acpi_refill_possible_map();
 }

 bool acpi_duplicate_processor_id(int proc_id)