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SubjectRe: [PATCH v9 03/12] mm: deferred_init_memmap improvements
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Hi Michal,

Are you OK, if I replace DEFERRED_FREE() macro with a function like this:

/*
* Helper for deferred_init_range, free the given range, and reset the
* counters
*/
static inline unsigned long __def_free(unsigned long *nr_free,
unsigned long *free_base_pfn,
struct page **page)
{
unsigned long nr = *nr_free;

deferred_free_range(*free_base_pfn, nr);
*free_base_pfn = 0;
*nr_free = 0;
*page = NULL;

return nr;
}

Since it is inline, and we operate with non-volatile counters, compiler
will be smart enough to remove all the unnecessary de-references. As a
plus, we won't be adding any new branches, and the code is still going
to stay compact.

Pasha

On 10/03/2017 11:15 AM, Pasha Tatashin wrote:
> Hi Michal,
>
>>
>> Please be explicit that this is possible only because we discard
>> memblock data later after 3010f876500f ("mm: discard memblock data
>> later"). Also be more explicit how the new code works.
>
> OK
>
>>
>> I like how the resulting code is more compact and smaller.
>
> That was the goal :)
>
>> for_each_free_mem_range also looks more appropriate but I really detest
>> the DEFERRED_FREE thingy. Maybe we can handle all that in a single goto
>> section. I know this is not an art but manipulating variables from
>> macros is more error prone and much more ugly IMHO.
>
> Sure, I can re-arrange to have a goto place. Function won't be as small,
> and if compiler is not smart enough we might end up with having more
> branches than what my current code has.
>
>>
>> please do not use macros. Btw. this deserves its own fix. I suspect that
>> no CONFIG_HOLES_IN_ZONE arch enables DEFERRED_STRUCT_PAGE_INIT but
>> purely from the review point of view it should be its own patch.
>
> Sure, I will submit this patch separately from the rest of the project.
> In my opinion DEFERRED_STRUCT_PAGE_INIT is the way of the future, so we
> should make sure it is working with as many configs as possible.
>
> Thank you,
> Pasha

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