Re: [PATCH] mm/migrate: Mark unmap_and_move() "noinline" to avoid ICE in gcc 4.7.3

[Lina Iyer <lina.iyer@linaro.org>]

On Thu, Apr 02 2015 at 15:12 -0600, Kevin Hilman wrote:
>On Thu, Apr 2, 2015 at 12:12 PM, Lina Iyer <lina.iyer@linaro.org> wrote:
>> On Wed, Apr 01 2015 at 15:57 -0600, Kevin Hilman wrote:
>>>
>>> Andrew Morton <akpm@linux-foundation.org> writes:
>>>
>>>> On Wed, 01 Apr 2015 10:47:49 +0100 Marc Zyngier <marc.zyngier@arm.com>
>>>> wrote:
>>>>
>>>>> > -static int unmap_and_move(new_page_t get_new_page, free_page_t
>>>>> > put_new_page,
>>>>> > -                     unsigned long private, struct page *page, int
>>>>> > force,
>>>>> > -                     enum migrate_mode mode)
>>>>> > +static noinline int unmap_and_move(new_page_t get_new_page,
>>>>> > +                                free_page_t put_new_page,
>>>>> > +                                unsigned long private, struct page
>>>>> > *page,
>>>>> > +                                int force, enum migrate_mode mode)
>>>>> >  {
>>>>> >       int rc = 0;
>>>>> >       int *result = NULL;
>>>>> >
>>>>>
>>>>> Ouch. That's really ugly. And on 32bit ARM, we end-up spilling half of
>>>>> the parameters on the stack, which is not going to help performance
>>>>> either (not that this would be useful on 32bit ARM anyway...).
>>>>>
>>>>> Any chance you could make this dependent on some compiler detection
>>>>> mechanism?
>>>>
>>>>
>>>> With my arm compiler (gcc-4.4.4) the patch makes no difference -
>>>> unmap_and_move() isn't being inlined anyway.
>>>>
>>>> How does this look?
>>>>
>>>> Kevin, could you please retest?  I might have fat-fingered something...
>>>
>>>
>>> Your patch on top of Geert's still compiles fine for me with gcc-4.7.3.
>>> However, I'm not sure how specific we can be on the versions.
>>>
>>> /me goes to test a few more compilers...   OK...
>>>
>>> ICE: 4.7.1, 4.7.3, 4.8.3
>>> OK: 4.6.3, 4.9.2, 4.9.3
>>>
>>> The diff below[2] on top of yours compiles fine here and at least covers
>>> the compilers I *know* to trigger the ICE.
>>
>>
>> I see ICE on arm-linux-gnueabi-gcc (Ubuntu/Linaro 4.7.4-2ubuntu1) 4.7.4
>>
>
>Thanks for checking.  I'm assuming my patch fixes it for your since
>that should catch any 4.7.x compiler.

Yes, thank you. This fixes it on 4.7.4
>
>Kevin