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SubjectRe: [RFC PATCH v3 00/12] Unify interrupt mode and setup it as soon as possible
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Hi Thomas,

At 05/23/2017 09:29 AM, Dou Liyang wrote:
> Dear Thomas,
>
> At 05/23/2017 04:23 AM, Thomas Gleixner wrote:
>> Dou,
>>
>> On Wed, 10 May 2017, Dou Liyang wrote:
>>
>>> According to Ingo's and Eric's advice[1,2], Try my best to optimize the
>>> init of interrupt delivery mode for x86.
>>
>> sorry for replying late. The patchset is not forgotten, it's on my todo
>> list and I'll tend to it latest next week.
>>
>
> I am very glad to hear that. :)
>
> I will check it again and wait for your advice.

I have come to a code bottleneck. Hope to spend your precious time and
let me move on.

Following is some test results for that patchset.

In a theoretical code analysis, the patchset can wrap the original
logic.

1) The original logic of the interrupt delivery mode setup:

-Step O_1) Keep in PIC mode or virtual wire mode:

Check (smp_found_config || !boot_cpu_has(X86_FEATURE_APIC))
true: PIC mode
false: virtual wire mode

-Step O_2) Try to switch to symmetric IO mode:
O_2_1) In up system:

-Check disable_apic
ture: *O_S_1* (original situation 1)
-Check whether there is a separate or integrated chip
don't has: *O_S_2*
-Check !smp_found_config
ture: *O_S_3*
-Others:
*O_S_4*

O_2_2) In smp-capable system:

-Check !smp_found_config && !acpi_lapic
true: goto *O_2_1)*
-Check if it is LAPIC
don't has: *O_S_5*
-Check !max_cpus
true: *O_S_6*
-read_apic_id() != boot_cpu_physical_apicid
true: *O_S_7*
-Others:
*O_S_8*

2) After that patchset, the new logic:

-Step N_1) Skip step O_1 and try to switch to the final interrupt mode
-Check disable_apic
ture: *N_S_1* (New situation 1)
-Check whether there is a separate or integrated chip
ture: *N_S_2*
-Check if (!smp_found_config)
ture: *N_S_3*
-Check !setup_max_cpus
ture: *N_S_4*
-Check read_apic_id() != boot_cpu_physical_apicid
ture: *N_S_5*
-Others:
*N_S_6*

O_S_1 is covered in N_S_1
O_S_2 is covered in N_S_2
O_S_3 is covered in N_S_3
O_S_4 is covered in N_S_6
O_S_5 is covered in N_S_2
O_S_6 is covered in N_S_4
O_S_7 is covered in N_S_5
O_S_8 is covered in N_S_6

--------------------------------------------

In the actual test, It also can work well in the situations of my test
matrix

The factors of test matrix:

X86 | SMP |LOCAL APIC|I/O APIC|UP_LATE_INIT|
----- |-----|----------|--------|------------|
32-bit| Y | Y | Y | Y |
64-bit| N | N | N | N |

disable_apic|X86_FEATURE_APIC|smp_found_config|
------------|----------------|----------------|
0 | 0 | 0 |
1 | 1 | 1 |

acpi_lapic|acpi_ioapic|setup_max_cpus|
----------|-----------|--------------|
0 | 0 | =0 |
1 | 1 | >0 |
>
> Thanks,
> Liyang.
>
>> Thanks,
>>
>> tglx
>>
>>
>>


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