Re: [PATCH v3 5/5] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid()

[Jia He <hejianet@gmail.com>]

On 3/28/2018 1:51 AM, Daniel Vacek Wrote:
> On Mon, Mar 26, 2018 at 5:02 AM, Jia He <hejianet@gmail.com> wrote:
>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>> where possible") optimized the loop in memmap_init_zone(). But there is
>> still some room for improvement. E.g. in early_pfn_valid(), if pfn and
>> pfn+1 are in the same memblock region, we can record the last returned
>> memblock region index and check check pfn++ is still in the same region.
>>
>> Currently it only improve the performance on arm64 and will have no
>> impact on other arches.
>>
>> Signed-off-by: Jia He <jia.he@hxt-semitech.com>
>> ---
>>   arch/x86/include/asm/mmzone_32.h |  2 +-
>>   include/linux/mmzone.h           | 12 +++++++++---
>>   mm/page_alloc.c                  |  2 +-
>>   3 files changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/mmzone_32.h b/arch/x86/include/asm/mmzone_32.h
>> index 73d8dd1..329d3ba 100644
>> --- a/arch/x86/include/asm/mmzone_32.h
>> +++ b/arch/x86/include/asm/mmzone_32.h
>> @@ -49,7 +49,7 @@ static inline int pfn_valid(int pfn)
>>          return 0;
>>   }
>>
>> -#define early_pfn_valid(pfn)   pfn_valid((pfn))
>> +#define early_pfn_valid(pfn, last_region_idx)  pfn_valid((pfn))
>>
>>   #endif /* CONFIG_DISCONTIGMEM */
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index d797716..3a686af 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -1267,9 +1267,15 @@ static inline int pfn_present(unsigned long pfn)
>>   })
>>   #else
>>   #define pfn_to_nid(pfn)                (0)
>> -#endif
>> +#endif /*CONFIG_NUMA*/
>> +
>> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +#define early_pfn_valid(pfn, last_region_idx) \
>> +                               pfn_valid_region(pfn, last_region_idx)
>> +#else
>> +#define early_pfn_valid(pfn, last_region_idx)  pfn_valid(pfn)
>> +#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>>
>> -#define early_pfn_valid(pfn)   pfn_valid(pfn)
>>   void sparse_init(void);
>>   #else
>>   #define sparse_init()  do {} while (0)
>> @@ -1288,7 +1294,7 @@ struct mminit_pfnnid_cache {
>>   };
>>
>>   #ifndef early_pfn_valid
>> -#define early_pfn_valid(pfn)   (1)
>> +#define early_pfn_valid(pfn, last_region_idx)  (1)
>>   #endif
>>
>>   void memory_present(int nid, unsigned long start, unsigned long end);
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 0bb0274..debccf3 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5484,7 +5484,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>>                  if (context != MEMMAP_EARLY)
>>                          goto not_early;
>>
>> -               if (!early_pfn_valid(pfn)) {
>> +               if (!early_pfn_valid(pfn, &idx)) {
>>   #if (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID)
>>                          /*
>>                           * Skip to the pfn preceding the next valid one (or
>> --
>> 2.7.4
>>
> Hmm, what about making index global variable instead of changing all
> the prototypes? Similar to early_pfnnid_cache for example. Something
> like:
>
> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
> extern int early_region_idx __meminitdata;
> #define early_pfn_valid(pfn) \
>                                 pfn_valid_region(pfn, &early_region_idx)
> #else
> #define early_pfn_valid(pfn)  pfn_valid(pfn)
> #endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>
> And move this to arch/arm64/include/asm/page.h ?
>
> --nX
>
Yes. ok with me

-- 
Cheers,
Jia