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SubjectRe: [PATCH v5 2/5] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn()
On Mon, Apr 2, 2018 at 8:57 AM, Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
> On 2 April 2018 at 04:30, 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. if pfn and pfn+1 are in the same
>> memblock region, we can simply pfn++ instead of doing the binary search
>> in memblock_next_valid_pfn.
>>
>> Signed-off-by: Jia He <jia.he@hxt-semitech.com>
>> ---
>> arch/arm/include/asm/page.h | 1 +
>> arch/arm/mm/init.c | 28 ++++++++++++++++++++++------
>> arch/arm64/include/asm/page.h | 1 +
>> arch/arm64/mm/init.c | 28 ++++++++++++++++++++++------
>> 4 files changed, 46 insertions(+), 12 deletions(-)
>>
>
> Could we put this in a shared file somewhere? This is the second patch
> where you put make identical changes to ARM and arm64.

Ard, I was wondering if we can actually have this changed to something
like CONFIG_MEMBLOCK_PFN_VALID and shared instead of it being arm
specific? Is there a reason it's only usable for arm? The rest is
dependent on this, hence I suggested to place it close-by. But
generalizing it all would make it a lot cleaner.

arch/arm/mm/init.c:196:
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
int pfn_valid(unsigned long pfn)
{
return memblock_is_map_memory(__pfn_to_phys(pfn));
}
EXPORT_SYMBOL(pfn_valid);
#endif

arch/arm64/mm/init.c:287:
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
int pfn_valid(unsigned long pfn)
{
return memblock_is_map_memory(pfn << PAGE_SHIFT);
}
EXPORT_SYMBOL(pfn_valid);
#endif

--nX

>> diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
>> index 489875c..f38909c 100644
>> --- a/arch/arm/include/asm/page.h
>> +++ b/arch/arm/include/asm/page.h
>> @@ -157,6 +157,7 @@ extern void copy_page(void *to, const void *from);
>> typedef struct page *pgtable_t;
>>
>> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +extern int early_region_idx;
>> extern int pfn_valid(unsigned long);
>> extern unsigned long memblock_next_valid_pfn(unsigned long pfn);
>> #define skip_to_last_invalid_pfn(pfn) (memblock_next_valid_pfn(pfn) - 1)
>> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
>> index 0fb85ca..06ed190 100644
>> --- a/arch/arm/mm/init.c
>> +++ b/arch/arm/mm/init.c
>> @@ -193,6 +193,8 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
>> }
>>
>> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +int early_region_idx __meminitdata = -1;
>> +
>> int pfn_valid(unsigned long pfn)
>> {
>> return memblock_is_map_memory(__pfn_to_phys(pfn));
>> @@ -203,28 +205,42 @@ EXPORT_SYMBOL(pfn_valid);
>> unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
>> {
>> struct memblock_type *type = &memblock.memory;
>> + struct memblock_region *regions = type->regions;
>> unsigned int right = type->cnt;
>> unsigned int mid, left = 0;
>> + unsigned long start_pfn, end_pfn;
>> phys_addr_t addr = PFN_PHYS(++pfn);
>>
>> + /* fast path, return pfn+1 if next pfn is in the same region */
>> + if (early_region_idx != -1) {
>> + start_pfn = PFN_DOWN(regions[early_region_idx].base);
>> + end_pfn = PFN_DOWN(regions[early_region_idx].base +
>> + regions[early_region_idx].size);
>> +
>> + if (pfn >= start_pfn && pfn < end_pfn)
>> + return pfn;
>> + }
>> +
>> + /* slow path, do the binary searching */
>> do {
>> mid = (right + left) / 2;
>>
>> - if (addr < type->regions[mid].base)
>> + if (addr < regions[mid].base)
>> right = mid;
>> - else if (addr >= (type->regions[mid].base +
>> - type->regions[mid].size))
>> + else if (addr >= (regions[mid].base + regions[mid].size))
>> left = mid + 1;
>> else {
>> - /* addr is within the region, so pfn is valid */
>> + early_region_idx = mid;
>> return pfn;
>> }
>> } while (left < right);
>>
>> if (right == type->cnt)
>> return -1UL;
>> - else
>> - return PHYS_PFN(type->regions[right].base);
>> +
>> + early_region_idx = right;
>> +
>> + return PHYS_PFN(regions[early_region_idx].base);
>> }
>> EXPORT_SYMBOL(memblock_next_valid_pfn);
>> #endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>> diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
>> index e57d3f2..f0d8c8e5 100644
>> --- a/arch/arm64/include/asm/page.h
>> +++ b/arch/arm64/include/asm/page.h
>> @@ -38,6 +38,7 @@ extern void clear_page(void *to);
>> typedef struct page *pgtable_t;
>>
>> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +extern int early_region_idx;
>> extern int pfn_valid(unsigned long);
>> extern unsigned long memblock_next_valid_pfn(unsigned long pfn);
>> #define skip_to_last_invalid_pfn(pfn) (memblock_next_valid_pfn(pfn) - 1)
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 13e43ff..342e4e2 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -285,6 +285,8 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>> #endif /* CONFIG_NUMA */
>>
>> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +int early_region_idx __meminitdata = -1;
>> +
>> int pfn_valid(unsigned long pfn)
>> {
>> return memblock_is_map_memory(pfn << PAGE_SHIFT);
>> @@ -295,28 +297,42 @@ EXPORT_SYMBOL(pfn_valid);
>> unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
>> {
>> struct memblock_type *type = &memblock.memory;
>> + struct memblock_region *regions = type->regions;
>> unsigned int right = type->cnt;
>> unsigned int mid, left = 0;
>> + unsigned long start_pfn, end_pfn;
>> phys_addr_t addr = PFN_PHYS(++pfn);
>>
>> + /* fast path, return pfn+1 if next pfn is in the same region */
>> + if (early_region_idx != -1) {
>> + start_pfn = PFN_DOWN(regions[early_region_idx].base);
>> + end_pfn = PFN_DOWN(regions[early_region_idx].base +
>> + regions[early_region_idx].size);
>> +
>> + if (pfn >= start_pfn && pfn < end_pfn)
>> + return pfn;
>> + }
>> +
>> + /* slow path, do the binary searching */
>> do {
>> mid = (right + left) / 2;
>>
>> - if (addr < type->regions[mid].base)
>> + if (addr < regions[mid].base)
>> right = mid;
>> - else if (addr >= (type->regions[mid].base +
>> - type->regions[mid].size))
>> + else if (addr >= (regions[mid].base + regions[mid].size))
>> left = mid + 1;
>> else {
>> - /* addr is within the region, so pfn is valid */
>> + early_region_idx = mid;
>> return pfn;
>> }
>> } while (left < right);
>>
>> if (right == type->cnt)
>> return -1UL;
>> - else
>> - return PHYS_PFN(type->regions[right].base);
>> +
>> + early_region_idx = right;
>> +
>> + return PHYS_PFN(regions[early_region_idx].base);
>> }
>> EXPORT_SYMBOL(memblock_next_valid_pfn);
>> #endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>> --
>> 2.7.4
>>

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